{"id":630,"date":"2024-06-01T17:14:43","date_gmt":"2024-06-01T09:14:43","guid":{"rendered":"https:\/\/levin.ink\/?p=630"},"modified":"2024-06-17T23:33:54","modified_gmt":"2024-06-17T15:33:54","slug":"js-3-5-%e5%87%bd%e6%95%b0%e8%bf%9b%e9%98%b6%e5%86%85%e5%ae%b9","status":"publish","type":"post","link":"https:\/\/levin.ink\/?p=630","title":{"rendered":"JS &#8211; 3-5 \u51fd\u6570\u8fdb\u9636\u5185\u5bb9"},"content":{"rendered":"<h1>\u9012\u5f52\u548c\u5806\u6808<\/h1>\n<p>...<\/p>\n<h1>Rest\u53c2\u6570\u548cSpread\u8bed\u6cd5<\/h1>\n<p>\u5728 JavaScript \u4e2d\uff0c\u5f88\u591a\u5185\u5efa\u51fd\u6570\u90fd\u652f\u6301\u4f20\u5165\u4efb\u610f\u6570\u91cf\u7684\u53c2\u6570\u3002<br \/>\n\u4f8b\u5982\uff1a<\/p>\n<ul>\n<li><code>Math.max(arg1, arg2, ..., argN)<\/code>\u00a0\u2014\u2014 \u8fd4\u56de\u53c2\u6570\u4e2d\u7684\u6700\u5927\u503c\u3002<\/li>\n<li><code>Object.assign(dest, src1, ..., srcN)<\/code>\u00a0\u2014\u2014 \u4f9d\u6b21\u5c06\u5c5e\u6027\u4ece\u00a0<code>src1..N<\/code>\u00a0\u590d\u5236\u5230\u00a0<code>dest<\/code>\u3002<\/li>\n<li>\u2026\u2026\u7b49\u3002<br \/>\n\u5728\u672c\u7ae0\u4e2d\uff0c\u6211\u4eec\u5c06\u5b66\u4e60\u5982\u4f55\u7f16\u5199\u652f\u6301\u4f20\u5165\u4efb\u610f\u6570\u91cf\u53c2\u6570\u7684\u51fd\u6570\uff0c\u4ee5\u53ca\u5982\u4f55\u5c06\u6570\u7ec4\u4f5c\u4e3a\u53c2\u6570\u4f20\u9012\u7ed9\u8fd9\u7c7b\u51fd\u6570\u3002<\/li>\n<\/ul>\n<h2>Rest\u53c2\u6570 ...<\/h2>\n<p>\u5728 JavaScript \u4e2d\uff0c\u65e0\u8bba\u51fd\u6570\u662f\u5982\u4f55\u5b9a\u4e49\u7684\uff0c\u4f60\u90fd\u53ef\u4ee5\u5728\u8c03\u7528\u5b83\u65f6\u4f20\u5165\u4efb\u610f\u6570\u91cf\u7684\u53c2\u6570\u3002<br \/>\n\u867d\u7136\u8fd9\u91cc\u8fd9\u4e2a\u51fd\u6570\u4e0d\u4f1a\u56e0\u4e3a\u4f20\u5165\u8fc7\u591a\u7684\u53c2\u6570\u800c\u62a5\u9519\u3002\u4f46\u662f\uff0c\u5f53\u7136\uff0c\u53ea\u6709\u524d\u4e24\u4e2a\u53c2\u6570\u88ab\u6c42\u548c\u4e86\u3002<br \/>\n\u6211\u4eec\u53ef\u4ee5\u5728\u51fd\u6570\u5b9a\u4e49\u4e2d\u58f0\u660e\u4e00\u4e2a\u6570\u7ec4\u6765\u6536\u96c6\u53c2\u6570\u3002\u8bed\u6cd5\u662f\u8fd9\u6837\u7684\uff1a<code>...\u53d8\u91cf\u540d<\/code>\uff0c\u8fd9\u5c06\u4f1a\u58f0\u660e\u4e00\u4e2a\u6570\u7ec4\u5e76\u6307\u5b9a\u5176\u540d\u79f0\uff0c\u5176\u4e2d\u5b58\u6709\u5269\u4f59\u7684\u53c2\u6570\u3002\u8fd9\u4e09\u4e2a\u70b9\u7684\u8bed\u4e49\u5c31\u662f\u201c\u6536\u96c6\u5269\u4f59\u7684\u53c2\u6570\u5e76\u5b58\u8fdb\u6307\u5b9a\u6570\u7ec4\u4e2d\u201d\u3002<\/p>\n<blockquote>\n<p>Rest \u53c2\u6570\u5fc5\u987b\u653e\u5230\u53c2\u6570\u5217\u8868\u7684\u672b\u5c3e<\/p>\n<\/blockquote>\n<h2>\u201carguments\u201d\u53d8\u91cf<\/h2>\n<p>\u6709\u4e00\u4e2a\u540d\u4e3a\u00a0<code>arguments<\/code>\u00a0\u7684\u7279\u6b8a\u7c7b\u6570\u7ec4\u5bf9\u8c61\u53ef\u4ee5\u5728\u51fd\u6570\u4e2d\u88ab\u8bbf\u95ee\uff0c\u8be5\u5bf9\u8c61\u4ee5\u53c2\u6570\u5728\u53c2\u6570\u5217\u8868\u4e2d\u7684\u7d22\u5f15\u4f5c\u4e3a\u952e\uff0c\u5b58\u50a8\u6240\u6709\u53c2\u6570\u3002<\/p>\n<pre><code class=\"language-js\">function showName() {\n  alert( arguments.length );\n  alert( arguments[0] );\n  alert( arguments[1] );\n\n  \/\/ \u5b83\u662f\u53ef\u904d\u5386\u7684\n  \/\/ for(let arg of arguments) alert(arg);\n}\n\n\/\/ \u4f9d\u6b21\u663e\u793a\uff1a2\uff0cJulius\uff0cCaesar\nshowName(&quot;Julius&quot;, &quot;Caesar&quot;);\n\n\/\/ \u4f9d\u6b21\u663e\u793a\uff1a1\uff0cIlya\uff0cundefined\uff08\u6ca1\u6709\u7b2c\u4e8c\u4e2a\u53c2\u6570\uff09\nshowName(&quot;Ilya&quot;);\n<\/code><\/pre>\n<p>\u5728\u8fc7\u53bb\uff0cJavaScript \u4e2d\u4e0d\u652f\u6301 rest \u53c2\u6570\u8bed\u6cd5\uff0c\u800c\u4f7f\u7528\u00a0<code>arguments<\/code>\u00a0\u662f\u83b7\u53d6\u51fd\u6570\u6240\u6709\u53c2\u6570\u7684\u552f\u4e00\u65b9\u6cd5\u3002\u73b0\u5728\u5b83\u4ecd\u7136\u6709\u6548\uff0c\u6211\u4eec\u53ef\u4ee5\u5728\u4e00\u4e9b\u8001\u4ee3\u7801\u91cc\u627e\u5230\u5b83\u3002<br \/>\n\u4f46\u7f3a\u70b9\u662f\uff0c\u5c3d\u7ba1\u00a0<code>arguments<\/code>\u00a0\u662f\u4e00\u4e2a\u7c7b\u6570\u7ec4\uff0c\u4e5f\u662f\u53ef\u8fed\u4ee3\u5bf9\u8c61\uff0c\u4f46\u5b83\u7ec8\u7a76\u4e0d\u662f\u6570\u7ec4\u3002\u5b83\u4e0d\u652f\u6301\u6570\u7ec4\u65b9\u6cd5\uff0c\u56e0\u6b64\u6211\u4eec\u4e0d\u80fd\u8c03\u7528\u00a0<code>arguments.map(...)<\/code>\u00a0\u7b49\u65b9\u6cd5\u3002<br \/>\n\u6b64\u5916\uff0c\u5b83\u59cb\u7ec8\u5305\u542b\u6240\u6709\u53c2\u6570\uff0c\u6211\u4eec\u4e0d\u80fd\u50cf\u4f7f\u7528 rest \u53c2\u6570\u90a3\u6837\u53ea\u622a\u53d6\u53c2\u6570\u7684\u4e00\u90e8\u5206\u3002<br \/>\n\u56e0\u6b64\uff0c\u5f53\u6211\u4eec\u9700\u8981\u8fd9\u4e9b\u529f\u80fd\u65f6\uff0c\u6700\u597d\u4f7f\u7528 rest \u53c2\u6570\u3002<\/p>\n<blockquote>\n<p>\u7bad\u5934\u51fd\u6570\u6ca1\u6709\u00a0<code>&quot;arguments&quot;<\/code><br \/>\n\u5982\u679c\u6211\u4eec\u5728\u7bad\u5934\u51fd\u6570\u4e2d\u8bbf\u95ee\u00a0<code>arguments<\/code>\uff0c\u8bbf\u95ee\u5230\u7684\u00a0<code>arguments<\/code>\u00a0\u5e76\u4e0d\u5c5e\u4e8e\u7bad\u5934\u51fd\u6570\uff0c\u800c\u662f\u5c5e\u4e8e\u7bad\u5934\u51fd\u6570\u5916\u90e8\u7684\u201c\u666e\u901a\u201d\u51fd\u6570\u3002<br \/>\n\u6211\u4eec\u5df2\u7ecf\u77e5\u9053\uff0c\u7bad\u5934\u51fd\u6570\u6ca1\u6709\u81ea\u8eab\u7684\u00a0<code>this<\/code>\u3002\u73b0\u5728\u6211\u4eec\u77e5\u9053\u4e86\u5b83\u4eec\u4e5f\u6ca1\u6709\u7279\u6b8a\u7684\u00a0<code>arguments<\/code>\u00a0\u5bf9\u8c61\u3002<\/p>\n<\/blockquote>\n<h2>Spread \u8bed\u6cd5<\/h2>\n<p>\u6211\u4eec\u521a\u521a\u770b\u5230\u4e86\u5982\u4f55\u4ece\u53c2\u6570\u5217\u8868\u4e2d\u83b7\u53d6\u6570\u7ec4\u3002<br \/>\n\u6709\u65f6\u5019\u6211\u4eec\u4e5f\u9700\u8981\u505a\u4e0e\u4e4b\u76f8\u53cd\u7684\u4e8b\u3002<br \/>\n\u4f8b\u5982\uff0c\u5185\u5efa\u51fd\u6570\u00a0<a href=\"https:\/\/developer.mozilla.org\/zh\/docs\/Web\/JavaScript\/Reference\/Global_Objects\/Math\/max\">Math.max<\/a>\u00a0\u4f1a\u8fd4\u56de\u53c2\u6570\u4e2d\u6700\u5927\u7684\u503c<br \/>\n\u5982\u679c\u6211\u4eec\u6709\u4e00\u4e2a\u6570\u7ec4\u00a0<code>[3, 5, 1]<\/code>\uff0c\u6211\u4eec\u8be5\u5982\u4f55\u7528\u5b83\u8c03\u7528\u00a0<code>Math.max<\/code>\u00a0\u5462\uff1f<br \/>\n\u76f4\u63a5\u201c\u539f\u6837\u201d\u4f20\u5165\u8fd9\u4e2a\u6570\u7ec4\u662f\u4e0d\u4f1a\u594f\u6548\u7684\uff0c\u56e0\u4e3a\u00a0<code>Math.max<\/code>\u00a0\u671f\u671b\u7684\u662f\u5217\u8868\u5f62\u5f0f\u7684\u6570\u503c\u578b\u53c2\u6570\uff0c\u800c\u4e0d\u662f\u4e00\u4e2a\u6570\u7ec4<br \/>\n\u6beb\u65e0\u7591\u95ee\uff0c\u6211\u4eec\u4e0d\u80fd\u624b\u52a8\u5730\u53bb\u4e00\u4e00\u8bbe\u7f6e\u53c2\u6570\u00a0<code>Math.max(arg[0], arg[1], arg[2])<\/code>\uff0c\u56e0\u4e3a\u6211\u4eec\u4e0d\u786e\u5b9a\u8fd9\u513f\u6709\u591a\u5c11\u4e2a\u3002\u5728\u4ee3\u7801\u6267\u884c\u65f6\uff0c\u53c2\u6570\u6570\u7ec4\u4e2d\u53ef\u80fd\u6709\u5f88\u591a\u4e2a\u5143\u7d20\uff0c\u4e5f\u53ef\u80fd\u4e00\u4e2a\u90fd\u6ca1\u6709\u3002\u800c\u4e14\uff0c\u8fd9\u6837\u7684\u4ee3\u7801\u4e5f\u5f88\u4e0d\u4f18\u96c5\u3002<br \/>\n<strong>Spread \u8bed\u6cd5<\/strong>\u00a0\u53ef\u4ee5\u89e3\u51b3\u8fd9\u4e2a\u95ee\u9898\uff01\u5b83\u770b\u8d77\u6765\u548c rest \u53c2\u6570\u5f88\u50cf\uff0c\u4e5f\u4f7f\u7528\u00a0<code>...<\/code>\uff0c\u4f46\u662f\u4e8c\u8005\u7684\u7528\u9014\u5b8c\u5168\u76f8\u53cd\u3002<br \/>\n\u5f53\u5728\u51fd\u6570\u8c03\u7528\u4e2d\u4f7f\u7528\u00a0<code>...arr<\/code>\u00a0\u65f6\uff0c\u5b83\u4f1a\u628a\u53ef\u8fed\u4ee3\u5bf9\u8c61\u00a0<code>arr<\/code>\u00a0\u201c\u5c55\u5f00\u201d\u5230\u53c2\u6570\u5217\u8868\u4e2d\u3002<br \/>\nSpread \u8bed\u6cd5\u5185\u90e8\u4f7f\u7528\u4e86\u8fed\u4ee3\u5668\u6765\u6536\u96c6\u5143\u7d20\uff0c\u4e0e\u00a0<code>for..of<\/code>\u00a0\u7684\u65b9\u5f0f\u76f8\u540c\u3002<br \/>\n\u56e0\u6b64\uff0c\u5bf9\u4e8e\u4e00\u4e2a\u5b57\u7b26\u4e32\uff0c<code>for..of<\/code>\u00a0\u4f1a\u9010\u4e2a\u8fd4\u56de\u8be5\u5b57\u7b26\u4e32\u4e2d\u7684\u5b57\u7b26\uff0c<code>...str<\/code>\u00a0\u4e5f\u540c\u7406\u4f1a\u5f97\u5230\u00a0<code>&quot;H&quot;,&quot;e&quot;,&quot;l&quot;,&quot;l&quot;,&quot;o&quot;<\/code>\u00a0\u8fd9\u6837\u7684\u7ed3\u679c\u3002\u968f\u540e\uff0c\u5b57\u7b26\u5217\u8868\u88ab\u4f20\u9012\u7ed9\u6570\u7ec4\u521d\u59cb\u5316\u5668\u00a0<code>[...str]<\/code>\u3002<br \/>\n\u5bf9\u4e8e\u8fd9\u4e2a\u7279\u5b9a\u4efb\u52a1\uff0c\u6211\u4eec\u8fd8\u53ef\u4ee5\u4f7f\u7528\u00a0<code>Array.from<\/code>\u00a0\u6765\u5b9e\u73b0\uff0c\u56e0\u4e3a\u8be5\u65b9\u6cd5\u4f1a\u5c06\u4e00\u4e2a\u53ef\u8fed\u4ee3\u5bf9\u8c61\uff08\u5982\u5b57\u7b26\u4e32\uff09\u8f6c\u6362\u4e3a\u6570\u7ec4<br \/>\n\u4e0d\u8fc7\u00a0<code>Array.from(obj)<\/code>\u00a0\u548c\u00a0<code>[...obj]<\/code>\u00a0\u5b58\u5728\u4e00\u4e2a\u7ec6\u5fae\u7684\u5dee\u522b\uff1a<\/p>\n<ul>\n<li><code>Array.from<\/code>\u00a0\u9002\u7528\u4e8e\u7c7b\u6570\u7ec4\u5bf9\u8c61\u4e5f\u9002\u7528\u4e8e\u53ef\u8fed\u4ee3\u5bf9\u8c61\u3002<\/li>\n<li>Spread \u8bed\u6cd5\u53ea\u9002\u7528\u4e8e\u53ef\u8fed\u4ee3\u5bf9\u8c61\u3002<br \/>\n\u56e0\u6b64\uff0c\u5bf9\u4e8e\u5c06\u4e00\u4e9b\u201c\u4e1c\u897f\u201d\u8f6c\u6362\u4e3a\u6570\u7ec4\u7684\u4efb\u52a1\uff0c<code>Array.from<\/code>\u00a0\u5f80\u5f80\u66f4\u901a\u7528\u3002<\/li>\n<\/ul>\n<h2>\u590d\u5236 array\/object<\/h2>\n<p>\u8fd8\u8bb0\u5f97\u6211\u4eec\u00a0<a href=\"https:\/\/zh.javascript.info\/object-copy#cloning-and-merging-object-assign\">\u4e4b\u524d\u8bb2\u8fc7\u7684<\/a>\u00a0<code>Object.assign()<\/code>\u00a0\u5417\uff1f<br \/>\n\u4f7f\u7528 spread \u8bed\u6cd5\u4e5f\u53ef\u4ee5\u505a\u540c\u6837\u7684\u4e8b\u60c5\uff08\u8bd1\u6ce8\uff1a\u4e5f\u5c31\u662f\u8fdb\u884c\u6d45\u62f7\u8d1d\uff09\u3002<\/p>\n<pre><code class=\"language-js\">let arrCopy = [...arr]; \/\/ \u5c06\u6570\u7ec4 spread \u5230\u53c2\u6570\u5217\u8868\u4e2d\n                        \/\/ \u7136\u540e\u5c06\u7ed3\u679c\u653e\u5230\u4e00\u4e2a\u65b0\u6570\u7ec4\nlet objCopy = { ...obj }; \/\/ \u5c06\u5bf9\u8c61 spread \u5230\u53c2\u6570\u5217\u8868\u4e2d\n                          \/\/ \u7136\u540e\u5c06\u7ed3\u679c\u8fd4\u56de\u5230\u4e00\u4e2a\u65b0\u5bf9\u8c61\n<\/code><\/pre>\n<p>\u8fd9\u79cd\u65b9\u5f0f\u6bd4\u4f7f\u7528\u00a0<code>let arrCopy = Object.assign([], arr)<\/code>\u00a0\u590d\u5236\u6570\u7ec4\uff0c\u6216\u4f7f\u7528\u00a0<code>let objCopy = Object.assign({}, obj)<\/code>\u00a0\u590d\u5236\u5bf9\u8c61\u6765\u8bf4\u66f4\u4e3a\u7b80\u4fbf\u3002\u56e0\u6b64\uff0c\u53ea\u8981\u60c5\u51b5\u5141\u8bb8\uff0c\u6211\u4eec\u503e\u5411\u4e8e\u4f7f\u7528\u5b83\u3002<\/p>\n<h1>\u53d8\u91cf\u4f5c\u7528\u57df\uff0c\u95ed\u5305<\/h1>\n<p>JavaScript \u662f\u4e00\u79cd\u975e\u5e38\u9762\u5411\u51fd\u6570\u7684\u8bed\u8a00\u3002\u5b83\u7ed9\u4e86\u6211\u4eec\u5f88\u5927\u7684\u81ea\u7531\u5ea6\u3002\u5728 JavaScript \u4e2d\uff0c\u6211\u4eec\u53ef\u4ee5\u968f\u65f6\u521b\u5efa\u51fd\u6570\uff0c\u53ef\u4ee5\u5c06\u51fd\u6570\u4f5c\u4e3a\u53c2\u6570\u4f20\u9012\u7ed9\u53e6\u4e00\u4e2a\u51fd\u6570\uff0c\u5e76\u5728\u5b8c\u5168\u4e0d\u540c\u7684\u4ee3\u7801\u4f4d\u7f6e\u8fdb\u884c\u8c03\u7528\u3002<br \/>\n\u6211\u4eec\u5df2\u7ecf\u77e5\u9053\u51fd\u6570\u53ef\u4ee5\u8bbf\u95ee\u5176\u5916\u90e8\u7684\u53d8\u91cf\u3002<br \/>\n\u4f46\u662f\uff0c\u5982\u679c\u5728\u51fd\u6570\u88ab\u521b\u5efa\u4e4b\u540e\uff0c\u5916\u90e8\u53d8\u91cf\u53d1\u751f\u4e86\u53d8\u5316\u4f1a\u600e\u6837\uff1f\u51fd\u6570\u4f1a\u83b7\u5f97\u65b0\u503c\u8fd8\u662f\u65e7\u503c\uff1f<br \/>\n\u5982\u679c\u5c06\u51fd\u6570\u4f5c\u4e3a\u53c2\u6570\uff08argument\uff09\u4f20\u9012\u5e76\u5728\u4ee3\u7801\u4e2d\u7684\u53e6\u4e00\u4e2a\u4f4d\u7f6e\u8c03\u7528\u5b83\uff0c\u8be5\u51fd\u6570\u5c06\u8bbf\u95ee\u7684\u662f\u65b0\u4f4d\u7f6e\u7684\u5916\u90e8\u53d8\u91cf\u5417\uff1f<br \/>\n\u8ba9\u6211\u4eec\u901a\u8fc7\u672c\u6587\u6765\u5b66\u4e60\u8fd9\u4e9b\u76f8\u5173\u77e5\u8bc6\uff0c\u4ee5\u4e86\u89e3\u5728\u8fd9\u4e9b\u573a\u666f\u4ee5\u53ca\u66f4\u590d\u6742\u7684\u573a\u666f\u4e0b\u5230\u5e95\u4f1a\u53d1\u751f\u4ec0\u4e48\u3002<\/p>\n<blockquote>\n<p>\u6211\u4eec\u5c06\u5728\u8fd9\u63a2\u8ba8\u4e00\u4e0b\u00a0<code>let\/const<\/code><br \/>\n\u5728 JavaScript \u4e2d\uff0c\u6709\u4e09\u79cd\u58f0\u660e\u53d8\u91cf\u7684\u65b9\u5f0f\uff1a<code>let<\/code>\uff0c<code>const<\/code>\uff08\u73b0\u4ee3\u65b9\u5f0f\uff09\uff0c<code>var<\/code>\uff08\u8fc7\u53bb\u7559\u4e0b\u6765\u7684\u65b9\u5f0f\uff09\u3002<\/p>\n<ul>\n<li>\u5728\u672c\u6587\u7684\u793a\u4f8b\u4e2d\uff0c\u6211\u4eec\u5c06\u4f7f\u7528\u00a0<code>let<\/code>\u00a0\u58f0\u660e\u53d8\u91cf\u3002<\/li>\n<li>\u7528\u00a0<code>const<\/code>\u00a0\u58f0\u660e\u7684\u53d8\u91cf\u7684\u884c\u4e3a\u4e5f\u76f8\u540c\uff08\u8bd1\u6ce8\uff1a\u4e0e\u00a0<code>let<\/code>\u00a0\u5728\u4f5c\u7528\u57df\u7b49\u7279\u6027\u4e0a\u662f\u76f8\u540c\u7684\uff09\uff0c\u56e0\u6b64\uff0c\u672c\u6587\u4e5f\u6d89\u53ca\u7528\u00a0<code>const<\/code>\u00a0\u8fdb\u884c\u53d8\u91cf\u58f0\u660e\u3002<\/li>\n<li>\u65e7\u7684\u00a0<code>var<\/code>\u00a0\u4e0e\u4e0a\u9762\u4e24\u4e2a\u6709\u7740\u660e\u663e\u7684\u533a\u522b\uff0c\u6211\u4eec\u5c06\u5728\u00a0<a href=\"https:\/\/zh.javascript.info\/var\">\u8001\u65e7\u7684 &quot;var&quot;<\/a>\u00a0\u4e2d\u8be6\u7ec6\u4ecb\u7ecd\u3002<\/li>\n<\/ul>\n<\/blockquote>\n<h2>\u4ee3\u7801\u5757<\/h2>\n<p>\u5982\u679c\u5728\u4ee3\u7801\u5757\u00a0<code>{...}<\/code>\u00a0\u5185\u58f0\u660e\u4e86\u4e00\u4e2a\u53d8\u91cf\uff0c\u90a3\u4e48\u8fd9\u4e2a\u53d8\u91cf\u53ea\u5728\u8be5\u4ee3\u7801\u5757\u5185\u53ef\u89c1\u3002\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u5b83\u6765\u9694\u79bb\u4e00\u6bb5\u4ee3\u7801\uff0c\u8be5\u6bb5\u4ee3\u7801\u6267\u884c\u81ea\u5df1\u7684\u4efb\u52a1\uff0c\u5e76\u4f7f\u7528\u4ec5\u5c5e\u4e8e\u81ea\u5df1\u7684\u53d8\u91cf<\/p>\n<pre><code class=\"language-js\">{\n  \/\/ \u4f7f\u7528\u5728\u4ee3\u7801\u5757\u5916\u4e0d\u53ef\u89c1\u7684\u5c40\u90e8\u53d8\u91cf\u505a\u4e00\u4e9b\u5de5\u4f5c\n\n  let message = &quot;Hello&quot;; \/\/ \u53ea\u5728\u6b64\u4ee3\u7801\u5757\u5185\u53ef\u89c1\n\n  alert(message); \/\/ Hello\n}\n\nalert(message); \/\/ Error: message is not defined\n<\/code><\/pre>\n<blockquote>\n<p>\u5982\u679c\u6ca1\u6709\u4ee3\u7801\u5757\u5219\u4f1a\u62a5\u9519<br \/>\n\u8bf7\u6ce8\u610f\uff0c\u5982\u679c\u6211\u4eec\u4f7f\u7528\u00a0<code>let<\/code>\u00a0\u5bf9\u5df2\u5b58\u5728\u7684\u53d8\u91cf\u8fdb\u884c\u91cd\u590d\u58f0\u660e\uff0c\u5982\u679c\u5bf9\u5e94\u7684\u53d8\u91cf\u6ca1\u6709\u5355\u72ec\u7684\u4ee3\u7801\u5757\uff0c\u5219\u4f1a\u51fa\u73b0\u9519\u8bef<\/p>\n<\/blockquote>\n<p>\u5bf9\u4e8e\u00a0<code>if<\/code>\uff0c<code>for<\/code>\u00a0\u548c\u00a0<code>while<\/code>\u00a0\u7b49\uff0c\u5728\u00a0<code>{...}<\/code>\u00a0\u4e2d\u58f0\u660e\u7684\u53d8\u91cf\u4e5f\u4ec5\u5728\u5185\u90e8\u53ef\u89c1\u5bf9\u4e8e\u00a0<code>for<\/code>\u00a0\u548c\u00a0<code>while<\/code>\u00a0\u5faa\u73af\u4e5f\u662f\u5982\u6b64<br \/>\n\u4ece\u89c6\u89c9\u4e0a\u770b\uff0c<code>let i<\/code>\u00a0\u4f4d\u4e8e\u00a0<code>{...}<\/code>\u00a0\u4e4b\u5916\u3002\u4f46\u662f\u00a0<code>for<\/code>\u00a0\u6784\u9020\u5728\u8fd9\u91cc\u5f88\u7279\u6b8a\uff1a\u5728\u5176\u4e2d\u58f0\u660e\u7684\u53d8\u91cf\u88ab\u89c6\u4e3a\u5757\u7684\u4e00\u90e8\u5206\u3002<\/p>\n<h2>\u5d4c\u5957\u51fd\u6570<\/h2>\n<p>\u5982\u679c\u4e00\u4e2a\u51fd\u6570\u662f\u5728\u53e6\u4e00\u4e2a\u51fd\u6570\u4e2d\u521b\u5efa\u7684\uff0c\u8be5\u51fd\u6570\u5c31\u88ab\u79f0\u4e3a\u201c\u5d4c\u5957\u201d\u51fd\u6570\u3002<br \/>\n\u5728 JavaScript \u4e2d\u5f88\u5bb9\u6613\u5b9e\u73b0\u8fd9\u4e00\u70b9\u3002<br \/>\n\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u5d4c\u5957\u6765\u7ec4\u7ec7\u4ee3\u7801<br \/>\n\u8fd9\u91cc\u521b\u5efa\u7684\u00a0<strong>\u5d4c\u5957<\/strong>\u00a0\u51fd\u6570\u00a0<code>getFullName()<\/code>\u00a0\u662f\u4e3a\u4e86\u66f4\u52a0\u65b9\u4fbf\u3002\u5b83\u53ef\u4ee5\u8bbf\u95ee\u5916\u90e8\u53d8\u91cf\uff0c\u56e0\u6b64\u53ef\u4ee5\u8fd4\u56de\u5168\u540d\u3002\u5d4c\u5957\u51fd\u6570\u5728 JavaScript \u4e2d\u5f88\u5e38\u89c1\u3002<br \/>\n\u66f4\u6709\u610f\u601d\u7684\u662f\uff0c\u53ef\u4ee5\u8fd4\u56de\u4e00\u4e2a\u5d4c\u5957\u51fd\u6570\uff1a\u4f5c\u4e3a\u4e00\u4e2a\u65b0\u5bf9\u8c61\u7684\u5c5e\u6027\u6216\u4f5c\u4e3a\u7ed3\u679c\u8fd4\u56de\u3002\u4e4b\u540e\u53ef\u4ee5\u5728\u5176\u4ed6\u5730\u65b9\u4f7f\u7528\u3002\u4e0d\u8bba\u5728\u54ea\u91cc\u8c03\u7528\uff0c\u5b83\u4ecd\u7136\u53ef\u4ee5\u8bbf\u95ee\u76f8\u540c\u7684\u5916\u90e8\u53d8\u91cf\u3002<br \/>\n\u4e0b\u9762\u7684\u00a0<code>makeCounter<\/code>\u00a0\u521b\u5efa\u4e86\u4e00\u4e2a \u201ccounter\u201d \u51fd\u6570\uff0c\u8be5\u51fd\u6570\u5728\u6bcf\u6b21\u8c03\u7528\u65f6\u8fd4\u56de\u4e0b\u4e00\u4e2a\u6570\u5b57\uff1a<\/p>\n<pre><code class=\"language-js\">function makeCounter() {\n  let count = 0;\n\n  return function() {\n    return count++;\n  };\n}\n\nlet counter = makeCounter();\n\nalert( counter() ); \/\/ 0\nalert( counter() ); \/\/ 1\nalert( counter() ); \/\/ 2\n<\/code><\/pre>\n<p>\u5c3d\u7ba1\u5f88\u7b80\u5355\uff0c\u4f46\u7a0d\u52a0\u53d8\u578b\u5c31\u5177\u6709\u5f88\u5f3a\u7684\u5b9e\u9645\u7528\u9014\uff0c\u6bd4\u5982\uff0c\u7528\u4f5c\u00a0<a href=\"https:\/\/en.wikipedia.org\/wiki\/Pseudorandom_number_generator\">\u968f\u673a\u6570\u751f\u6210\u5668<\/a>\u00a0\u4ee5\u751f\u6210\u7528\u4e8e\u81ea\u52a8\u5316\u6d4b\u8bd5\u7684\u968f\u673a\u6570\u503c\u3002<br \/>\n\u8fd9\u662f\u5982\u4f55\u8fd0\u4f5c\u7684\u5462\uff1f\u5982\u679c\u6211\u4eec\u521b\u5efa\u591a\u4e2a\u8ba1\u6570\u5668\uff0c\u5b83\u4eec\u4f1a\u662f\u72ec\u7acb\u7684\u5417\uff1f\u8fd9\u91cc\u7684\u53d8\u91cf\u662f\u600e\u4e48\u56de\u4e8b\uff1f<br \/>\n\u7406\u89e3\u8fd9\u4e9b\u5185\u5bb9\u5bf9\u4e8e\u638c\u63e1 JavaScript \u7684\u6574\u4f53\u77e5\u8bc6\u5f88\u6709\u5e2e\u52a9\uff0c\u5e76\u4e14\u5bf9\u4e8e\u5e94\u5bf9\u66f4\u590d\u6742\u7684\u573a\u666f\u4e5f\u5f88\u6709\u76ca\u5904\u3002\u56e0\u6b64\uff0c\u8ba9\u6211\u4eec\u7ee7\u7eed\u6df1\u5165\u63a2\u7a76\u3002<\/p>\n<h2>\u8bcd\u6cd5\u73af\u5883<\/h2>\n<blockquote>\n<p>\u524d\u65b9\u9ad8\u80fd\uff01<br \/>\n\u4e00\u5927\u6ce2\u6df1\u5165\u7684\u6280\u672f\u8bb2\u89e3\u5373\u5c06\u5230\u6765\u3002<br \/>\n\u5c3d\u7ba1\u6211\u5f88\u60f3\u907f\u514d\u7f16\u7a0b\u8bed\u8a00\u7684\u4e00\u4e9b\u5e95\u5c42\u7ec6\u8282\uff0c\u4f46\u662f\u5982\u679c\u6ca1\u6709\u5b83\u4eec\uff0c\u6211\u4eec\u5c31\u65e0\u6cd5\u5b8c\u6574\u5730\u7406\u89e3\u8bcd\u6cd5\u4f5c\u7528\u57df\uff0c\u6240\u4ee5\u6211\u4eec\u8fd9\u5c31\u5f00\u59cb\u5427\uff01<\/p>\n<\/blockquote>\n<h3>Step 1.\u53d8\u91cf<\/h3>\n<p>\u5728 JavaScript \u4e2d\uff0c\u6bcf\u4e2a\u8fd0\u884c\u7684\u51fd\u6570\uff0c\u4ee3\u7801\u5757\u00a0<code>{...}<\/code>\u00a0\u4ee5\u53ca\u6574\u4e2a\u811a\u672c\uff0c\u90fd\u6709\u4e00\u4e2a\u88ab\u79f0\u4e3a\u00a0<strong>\u8bcd\u6cd5\u73af\u5883\uff08Lexical Environment\uff09<\/strong>\u00a0\u7684\u5185\u90e8\uff08\u9690\u85cf\uff09\u7684\u5173\u8054\u5bf9\u8c61\u3002<br \/>\n\u8bcd\u6cd5\u73af\u5883\u5bf9\u8c61\u7531\u4e24\u90e8\u5206\u7ec4\u6210\uff1a<\/p>\n<ol>\n<li><strong>\u73af\u5883\u8bb0\u5f55\uff08Environment Record\uff09<\/strong>\u00a0\u2014\u2014 \u4e00\u4e2a\u5b58\u50a8\u6240\u6709\u5c40\u90e8\u53d8\u91cf\u4f5c\u4e3a\u5176\u5c5e\u6027\uff08\u5305\u62ec\u4e00\u4e9b\u5176\u4ed6\u4fe1\u606f\uff0c\u4f8b\u5982\u00a0<code>this<\/code>\u00a0\u7684\u503c\uff09\u7684\u5bf9\u8c61\u3002<\/li>\n<li>\u5bf9\u00a0<strong>\u5916\u90e8\u8bcd\u6cd5\u73af\u5883<\/strong>\u00a0\u7684\u5f15\u7528\uff0c\u4e0e\u5916\u90e8\u4ee3\u7801\u76f8\u5173\u8054\u3002<\/li>\n<\/ol>\n<blockquote>\n<p>\u8bcd\u6cd5\u73af\u5883\u662f\u4e00\u4e2a\u89c4\u8303\u5bf9\u8c61<br \/>\n\u201c\u8bcd\u6cd5\u73af\u5883\u201d\u662f\u4e00\u4e2a\u89c4\u8303\u5bf9\u8c61\uff08specification object\uff09\uff1a\u5b83\u53ea\u5b58\u5728\u4e8e\u00a0<a href=\"https:\/\/tc39.es\/ecma262\/#sec-lexical-environments\">\u8bed\u8a00\u89c4\u8303<\/a>\u00a0\u7684\u201c\u7406\u8bba\u201d\u5c42\u9762\uff0c\u7528\u4e8e\u63cf\u8ff0\u4e8b\u7269\u662f\u5982\u4f55\u5de5\u4f5c\u7684\u3002\u6211\u4eec\u65e0\u6cd5\u5728\u4ee3\u7801\u4e2d\u83b7\u53d6\u8be5\u5bf9\u8c61\u5e76\u76f4\u63a5\u5bf9\u5176\u8fdb\u884c\u64cd\u4f5c\u3002<br \/>\n\u4f46 JavaScript \u5f15\u64ce\u540c\u6837\u53ef\u4ee5\u4f18\u5316\u5b83\uff0c\u6bd4\u5982\u6e05\u9664\u672a\u88ab\u4f7f\u7528\u7684\u53d8\u91cf\u4ee5\u8282\u7701\u5185\u5b58\u548c\u6267\u884c\u5176\u4ed6\u5185\u90e8\u6280\u5de7\u7b49\uff0c\u4f46\u663e\u6027\u884c\u4e3a\u5e94\u8be5\u662f\u548c\u4e0a\u8ff0\u7684\u65e0\u5dee\u3002<\/p>\n<\/blockquote>\n<h3>Step 2.\u51fd\u6570\u58f0\u660e<\/h3>\n<p>\u4e00\u4e2a\u51fd\u6570\u5176\u5b9e\u4e5f\u662f\u4e00\u4e2a\u503c\uff0c\u5c31\u50cf\u53d8\u91cf\u4e00\u6837\u3002<br \/>\n<strong>\u4e0d\u540c\u4e4b\u5904\u5728\u4e8e\u51fd\u6570\u58f0\u660e\u7684\u521d\u59cb\u5316\u4f1a\u88ab\u7acb\u5373\u5b8c\u6210\u3002<\/strong><br \/>\n\u5f53\u521b\u5efa\u4e86\u4e00\u4e2a\u8bcd\u6cd5\u73af\u5883\uff08Lexical Environment\uff09\u65f6\uff0c\u51fd\u6570\u58f0\u660e\u4f1a\u7acb\u5373\u53d8\u4e3a\u5373\u7528\u578b\u51fd\u6570\uff08\u4e0d\u50cf\u00a0<code>let<\/code>\u00a0\u90a3\u6837\u76f4\u5230\u58f0\u660e\u5904\u624d\u53ef\u7528\uff09\u3002<br \/>\n\u6b63\u5e38\u6765\u8bf4\uff0c\u8fd9\u79cd\u884c\u4e3a\u4ec5\u9002\u7528\u4e8e\u51fd\u6570\u58f0\u660e\uff0c\u800c\u4e0d\u9002\u7528\u4e8e\u6211\u4eec\u5c06\u51fd\u6570\u5206\u914d\u7ed9\u53d8\u91cf\u7684\u51fd\u6570\u8868\u8fbe\u5f0f\uff0c\u4f8b\u5982\u00a0<code>let say = function(name)...<\/code>\u3002<\/p>\n<h3>Step 3.\u5185\u90e8\u548c\u5916\u90e8\u7684\u8bcd\u6cd5\u73af\u5883<\/h3>\n<p>\u5728\u4e00\u4e2a\u51fd\u6570\u8fd0\u884c\u65f6\uff0c\u5728\u8c03\u7528\u521a\u5f00\u59cb\u65f6\uff0c\u4f1a\u81ea\u52a8\u521b\u5efa\u4e00\u4e2a\u65b0\u7684\u8bcd\u6cd5\u73af\u5883\u4ee5\u5b58\u50a8\u8fd9\u4e2a\u8c03\u7528\u7684\u5c40\u90e8\u53d8\u91cf\u548c\u53c2\u6570\u3002<br \/>\n\u5728\u8fd9\u4e2a\u51fd\u6570\u8c03\u7528\u671f\u95f4\uff0c\u6211\u4eec\u6709\u4e24\u4e2a\u8bcd\u6cd5\u73af\u5883\uff1a\u5185\u90e8\u4e00\u4e2a\uff08\u7528\u4e8e\u51fd\u6570\u8c03\u7528\uff09\u548c\u5916\u90e8\u4e00\u4e2a\uff08\u5168\u5c40\uff09\uff1a<\/p>\n<ul>\n<li>\u5185\u90e8\u8bcd\u6cd5\u73af\u5883\u4e0e\u00a0<code>say<\/code>\u00a0\u7684\u5f53\u524d\u6267\u884c\u76f8\u5bf9\u5e94\u3002\u5b83\u5177\u6709\u4e00\u4e2a\u5355\u72ec\u7684\u5c5e\u6027\uff1a<code>name<\/code>\uff0c\u51fd\u6570\u7684\u53c2\u6570\u3002\u6211\u4eec\u8c03\u7528\u7684\u662f\u00a0<code>say(&quot;John&quot;)<\/code>\uff0c\u6240\u4ee5\u00a0<code>name<\/code>\u00a0\u7684\u503c\u4e3a\u00a0<code>&quot;John&quot;<\/code>\u3002<\/li>\n<li>\u5916\u90e8\u8bcd\u6cd5\u73af\u5883\u662f\u5168\u5c40\u8bcd\u6cd5\u73af\u5883\u3002\u5b83\u5177\u6709\u00a0<code>phrase<\/code>\u00a0\u53d8\u91cf\u548c\u51fd\u6570\u672c\u8eab\u3002<br \/>\n\u5185\u90e8\u8bcd\u6cd5\u73af\u5883\u5f15\u7528\u4e86\u00a0<code>outer<\/code>\u3002<br \/>\n<strong>\u5f53\u4ee3\u7801\u8981\u8bbf\u95ee\u4e00\u4e2a\u53d8\u91cf\u65f6 \u2014\u2014 \u9996\u5148\u4f1a\u641c\u7d22\u5185\u90e8\u8bcd\u6cd5\u73af\u5883\uff0c\u7136\u540e\u641c\u7d22\u5916\u90e8\u73af\u5883\uff0c\u7136\u540e\u641c\u7d22\u66f4\u5916\u90e8\u7684\u73af\u5883\uff0c\u4ee5\u6b64\u7c7b\u63a8\uff0c\u76f4\u5230\u5168\u5c40\u8bcd\u6cd5\u73af\u5883\u3002<\/strong><br \/>\n\u5982\u679c\u5728\u4efb\u4f55\u5730\u65b9\u90fd\u627e\u4e0d\u5230\u8fd9\u4e2a\u53d8\u91cf\uff0c\u90a3\u4e48\u5728\u4e25\u683c\u6a21\u5f0f\u4e0b\u5c31\u4f1a\u62a5\u9519\uff08\u5728\u975e\u4e25\u683c\u6a21\u5f0f\u4e0b\uff0c\u4e3a\u4e86\u5411\u4e0b\u517c\u5bb9\uff0c\u7ed9\u672a\u5b9a\u4e49\u7684\u53d8\u91cf\u8d4b\u503c\u4f1a\u521b\u5efa\u4e00\u4e2a\u5168\u5c40\u53d8\u91cf\uff09\u3002<\/li>\n<\/ul>\n<h3>Step 4.\u8fd4\u56de\u51fd\u6570<\/h3>\n<p>\u8ba9\u6211\u4eec\u56de\u5230\u00a0<code>makeCounter<\/code>\u00a0\u8fd9\u4e2a\u4f8b\u5b50\u3002<br \/>\n\u5728\u6bcf\u6b21\u00a0<code>makeCounter()<\/code>\u00a0\u8c03\u7528\u7684\u5f00\u59cb\uff0c\u90fd\u4f1a\u521b\u5efa\u4e00\u4e2a\u65b0\u7684\u8bcd\u6cd5\u73af\u5883\u5bf9\u8c61\uff0c\u4ee5\u5b58\u50a8\u8be5\u00a0<code>makeCounter<\/code>\u00a0\u8fd0\u884c\u65f6\u7684\u53d8\u91cf\u3002<br \/>\n\u4e0d\u540c\u7684\u662f\uff0c\u5728\u6267\u884c\u00a0<code>makeCounter()<\/code>\u00a0\u7684\u8fc7\u7a0b\u4e2d\u521b\u5efa\u4e86\u4e00\u4e2a\u4ec5\u5360\u4e00\u884c\u7684\u5d4c\u5957\u51fd\u6570\uff1a<code>return count++<\/code>\u3002\u6211\u4eec\u5c1a\u672a\u8fd0\u884c\u5b83\uff0c\u4ec5\u521b\u5efa\u4e86\u5b83\u3002<br \/>\n\u6240\u6709\u7684\u51fd\u6570\u5728\u201c\u8bde\u751f\u201d\u65f6\u90fd\u4f1a\u8bb0\u4f4f\u521b\u5efa\u5b83\u4eec\u7684\u8bcd\u6cd5\u73af\u5883\u3002\u4ece\u6280\u672f\u4e0a\u8bb2\uff0c\u8fd9\u91cc\u6ca1\u6709\u4ec0\u4e48\u9b54\u6cd5\uff1a\u6240\u6709\u51fd\u6570\u90fd\u6709\u540d\u4e3a\u00a0<code>[[Environment]]<\/code>\u00a0\u7684\u9690\u85cf\u5c5e\u6027\uff0c\u8be5\u5c5e\u6027\u4fdd\u5b58\u4e86\u5bf9\u521b\u5efa\u8be5\u51fd\u6570\u7684\u8bcd\u6cd5\u73af\u5883\u7684\u5f15\u7528\u3002<br \/>\n\u56e0\u6b64\uff0c<code>counter.[[Environment]]<\/code>\u00a0\u6709\u5bf9\u00a0<code>{count: 0}<\/code>\u00a0\u8bcd\u6cd5\u73af\u5883\u7684\u5f15\u7528\u3002\u8fd9\u5c31\u662f\u51fd\u6570\u8bb0\u4f4f\u5b83\u521b\u5efa\u4e8e\u4f55\u5904\u7684\u65b9\u5f0f\uff0c\u4e0e\u51fd\u6570\u88ab\u5728\u54ea\u513f\u8c03\u7528\u65e0\u5173\u3002<code>[[Environment]]<\/code>\u00a0\u5f15\u7528\u5728\u51fd\u6570\u521b\u5efa\u65f6\u88ab\u8bbe\u7f6e\u5e76\u6c38\u4e45\u4fdd\u5b58\u3002<br \/>\n\u7a0d\u540e\uff0c\u5f53\u8c03\u7528\u00a0<code>counter()<\/code>\u00a0\u65f6\uff0c\u4f1a\u4e3a\u8be5\u8c03\u7528\u521b\u5efa\u4e00\u4e2a\u65b0\u7684\u8bcd\u6cd5\u73af\u5883\uff0c\u5e76\u4e14\u5176\u5916\u90e8\u8bcd\u6cd5\u73af\u5883\u5f15\u7528\u83b7\u53d6\u4e8e\u00a0<code>counter.[[Environment]]<\/code><br \/>\n\u73b0\u5728\uff0c\u5f53\u00a0<code>counter()<\/code>\u00a0\u4e2d\u7684\u4ee3\u7801\u67e5\u627e\u00a0<code>count<\/code>\u00a0\u53d8\u91cf\u65f6\uff0c\u5b83\u9996\u5148\u641c\u7d22\u81ea\u5df1\u7684\u8bcd\u6cd5\u73af\u5883\uff08\u4e3a\u7a7a\uff0c\u56e0\u4e3a\u90a3\u91cc\u6ca1\u6709\u5c40\u90e8\u53d8\u91cf\uff09\uff0c\u7136\u540e\u662f\u5916\u90e8\u00a0<code>makeCounter()<\/code>\u00a0\u7684\u8bcd\u6cd5\u73af\u5883\uff0c\u5e76\u4e14\u5728\u54ea\u91cc\u627e\u5230\u5c31\u5728\u54ea\u91cc\u4fee\u6539\u3002<br \/>\n<strong>\u5728\u53d8\u91cf\u6240\u5728\u7684\u8bcd\u6cd5\u73af\u5883\u4e2d\u66f4\u65b0\u53d8\u91cf\u3002<\/strong><\/p>\n<blockquote>\n<p>\u95ed\u5305<br \/>\n\u5f00\u53d1\u8005\u901a\u5e38\u5e94\u8be5\u90fd\u77e5\u9053\u201c\u95ed\u5305\u201d\u8fd9\u4e2a\u901a\u7528\u7684\u7f16\u7a0b\u672f\u8bed\u3002<br \/>\n<a href=\"https:\/\/en.wikipedia.org\/wiki\/Closure_(computer_programming)\">\u95ed\u5305<\/a>\u00a0\u662f\u6307\u4e00\u4e2a\u51fd\u6570\u53ef\u4ee5\u8bb0\u4f4f\u5176\u5916\u90e8\u53d8\u91cf\u5e76\u53ef\u4ee5\u8bbf\u95ee\u8fd9\u4e9b\u53d8\u91cf\u3002\u5728\u67d0\u4e9b\u7f16\u7a0b\u8bed\u8a00\u4e2d\uff0c\u8fd9\u662f\u4e0d\u53ef\u80fd\u7684\uff0c\u6216\u8005\u5e94\u8be5\u4ee5\u4e00\u79cd\u7279\u6b8a\u7684\u65b9\u5f0f\u7f16\u5199\u51fd\u6570\u6765\u5b9e\u73b0\u3002\u4f46\u5982\u4e0a\u6240\u8ff0\uff0c\u5728 JavaScript \u4e2d\uff0c\u6240\u6709\u51fd\u6570\u90fd\u662f\u5929\u751f\u95ed\u5305\u7684\uff08\u53ea\u6709\u4e00\u4e2a\u4f8b\u5916\uff0c\u5c06\u5728\u00a0<a href=\"https:\/\/zh.javascript.info\/new-function\">&quot;new Function&quot; \u8bed\u6cd5<\/a>\u00a0\u4e2d\u8bb2\u5230\uff09\u3002<br \/>\n\u4e5f\u5c31\u662f\u8bf4\uff1aJavaScript \u4e2d\u7684\u51fd\u6570\u4f1a\u81ea\u52a8\u901a\u8fc7\u9690\u85cf\u7684\u00a0<code>[[Environment]]<\/code>\u00a0\u5c5e\u6027\u8bb0\u4f4f\u521b\u5efa\u5b83\u4eec\u7684\u4f4d\u7f6e\uff0c\u6240\u4ee5\u5b83\u4eec\u90fd\u53ef\u4ee5\u8bbf\u95ee\u5916\u90e8\u53d8\u91cf\u3002<br \/>\n\u5728\u9762\u8bd5\u65f6\uff0c\u524d\u7aef\u5f00\u53d1\u8005\u901a\u5e38\u4f1a\u88ab\u95ee\u5230\u201c\u4ec0\u4e48\u662f\u95ed\u5305\uff1f\u201d\uff0c\u6b63\u786e\u7684\u56de\u7b54\u5e94\u8be5\u662f\u95ed\u5305\u7684\u5b9a\u4e49\uff0c\u5e76\u89e3\u91ca\u6e05\u695a\u4e3a\u4ec0\u4e48 JavaScript \u4e2d\u7684\u6240\u6709\u51fd\u6570\u90fd\u662f\u95ed\u5305\u7684\uff0c\u4ee5\u53ca\u53ef\u80fd\u7684\u5173\u4e8e\u00a0<code>[[Environment]]<\/code>\u00a0\u5c5e\u6027\u548c\u8bcd\u6cd5\u73af\u5883\u539f\u7406\u7684\u6280\u672f\u7ec6\u8282\u3002<\/p>\n<\/blockquote>\n<h2>\u5783\u573e\u6536\u96c6<\/h2>\n<p>\u901a\u5e38\uff0c\u51fd\u6570\u8c03\u7528\u5b8c\u6210\u540e\uff0c\u4f1a\u5c06\u8bcd\u6cd5\u73af\u5883\u548c\u5176\u4e2d\u7684\u6240\u6709\u53d8\u91cf\u4ece\u5185\u5b58\u4e2d\u5220\u9664\u3002\u56e0\u4e3a\u73b0\u5728\u6ca1\u6709\u4efb\u4f55\u5bf9\u5b83\u4eec\u7684\u5f15\u7528\u4e86\u3002\u4e0e JavaScript \u4e2d\u7684\u4efb\u4f55\u5176\u4ed6\u5bf9\u8c61\u4e00\u6837\uff0c\u8bcd\u6cd5\u73af\u5883\u4ec5\u5728\u53ef\u8fbe\u65f6\u624d\u4f1a\u88ab\u4fdd\u7559\u5728\u5185\u5b58\u4e2d\u3002<br \/>\n\u4f46\u662f\uff0c\u5982\u679c\u6709\u4e00\u4e2a\u5d4c\u5957\u7684\u51fd\u6570\u5728\u51fd\u6570\u7ed3\u675f\u540e\u4ecd\u53ef\u8fbe\uff0c\u5219\u5b83\u5c06\u5177\u6709\u5f15\u7528\u8bcd\u6cd5\u73af\u5883\u7684\u00a0<code>[[Environment]]<\/code>\u00a0\u5c5e\u6027\u3002<br \/>\n\u8bf7\u6ce8\u610f\uff0c\u5982\u679c\u591a\u6b21\u8c03\u7528\u00a0<code>f()<\/code>\uff0c\u5e76\u4e14\u8fd4\u56de\u7684\u51fd\u6570\u88ab\u4fdd\u5b58\uff0c\u90a3\u4e48\u6240\u6709\u76f8\u5e94\u7684\u8bcd\u6cd5\u73af\u5883\u5bf9\u8c61\u4e5f\u4f1a\u4fdd\u7559\u5728\u5185\u5b58\u4e2d\u3002<br \/>\n\u5f53\u8bcd\u6cd5\u73af\u5883\u5bf9\u8c61\u53d8\u5f97\u4e0d\u53ef\u8fbe\u65f6\uff0c\u5b83\u5c31\u4f1a\u6b7b\u53bb\uff08\u5c31\u50cf\u5176\u4ed6\u4efb\u4f55\u5bf9\u8c61\u4e00\u6837\uff09\u3002\u6362\u53e5\u8bdd\u8bf4\uff0c\u5b83\u4ec5\u5728\u81f3\u5c11\u6709\u4e00\u4e2a\u5d4c\u5957\u51fd\u6570\u5f15\u7528\u5b83\u65f6\u624d\u5b58\u5728\u3002<\/p>\n<h3>\u5b9e\u9645\u5f00\u53d1\u4e2d\u7684\u4f18\u5316<\/h3>\n<p>\u6b63\u5982\u6211\u4eec\u6240\u770b\u5230\u7684\uff0c\u7406\u8bba\u4e0a\u5f53\u51fd\u6570\u53ef\u8fbe\u65f6\uff0c\u5b83\u5916\u90e8\u7684\u6240\u6709\u53d8\u91cf\u4e5f\u90fd\u5c06\u5b58\u5728\u3002<br \/>\n\u4f46\u5728\u5b9e\u9645\u4e2d\uff0cJavaScript \u5f15\u64ce\u4f1a\u8bd5\u56fe\u4f18\u5316\u5b83\u3002\u5b83\u4eec\u4f1a\u5206\u6790\u53d8\u91cf\u7684\u4f7f\u7528\u60c5\u51b5\uff0c\u5982\u679c\u4ece\u4ee3\u7801\u4e2d\u53ef\u4ee5\u660e\u663e\u770b\u51fa\u6709\u672a\u4f7f\u7528\u7684\u5916\u90e8\u53d8\u91cf\uff0c\u90a3\u4e48\u5c31\u4f1a\u5c06\u5176\u5220\u9664\u3002<br \/>\n<strong>\u5728 V8\uff08Chrome\uff0cEdge\uff0cOpera\uff09\u4e2d\u7684\u4e00\u4e2a\u91cd\u8981\u7684\u526f\u4f5c\u7528\u662f\uff0c\u6b64\u7c7b\u53d8\u91cf\u5728\u8c03\u8bd5\u4e2d\u5c06\u4e0d\u53ef\u7528\u3002<\/strong><br \/>\n\u6253\u5f00 Chrome \u6d4f\u89c8\u5668\u7684\u5f00\u53d1\u8005\u5de5\u5177\uff0c\u5e76\u5c1d\u8bd5\u8fd0\u884c\u4e0b\u9762\u7684\u4ee3\u7801\u3002<br \/>\n\u5f53\u4ee3\u7801\u6267\u884c\u6682\u505c\u65f6\uff0c\u5728\u63a7\u5236\u53f0\u4e2d\u8f93\u5165\u00a0<code>alert(value)<\/code>\u3002<\/p>\n<pre><code class=\"language-js\">function f() {\n  let value = Math.random();\n\n  function g() {\n    debugger; \/\/ \u5728 Console \u4e2d\uff1a\u8f93\u5165 alert(value); No such variable!\n  }\n\n  return g;\n}\n\nlet g = f();\ng();\n<\/code><\/pre>\n<p>\u6b63\u5982\u4f60\u6240\u89c1\u7684 \u2014\u2014 No such variable! \u7406\u8bba\u4e0a\uff0c\u5b83\u5e94\u8be5\u662f\u53ef\u4ee5\u8bbf\u95ee\u7684\uff0c\u4f46\u5f15\u64ce\u628a\u5b83\u4f18\u5316\u6389\u4e86\u3002<br \/>\n\u8fd9\u53ef\u80fd\u4f1a\u5bfc\u81f4\u6709\u8da3\u7684\uff08\u5982\u679c\u4e0d\u662f\u90a3\u4e48\u8017\u65f6\u7684\uff09\u8c03\u8bd5\u95ee\u9898\u3002\u5176\u4e2d\u4e4b\u4e00 \u2014\u2014 \u6211\u4eec\u53ef\u4ee5\u770b\u5230\u7684\u662f\u4e00\u4e2a\u540c\u540d\u7684\u5916\u90e8\u53d8\u91cf\uff0c\u800c\u4e0d\u662f\u9884\u671f\u7684\u53d8\u91cf<br \/>\nV8 \u5f15\u64ce\u7684\u8fd9\u4e2a\u7279\u6027\u4f60\u771f\u7684\u5e94\u8be5\u77e5\u9053\u3002\u5982\u679c\u4f60\u8981\u4f7f\u7528 Chrome\/Edge\/Opera \u8fdb\u884c\u4ee3\u7801\u8c03\u8bd5\uff0c\u8fdf\u65e9\u4f1a\u9047\u5230\u8fd9\u6837\u7684\u95ee\u9898\u3002<br \/>\n\u8fd9\u4e0d\u662f\u8c03\u8bd5\u5668\u7684 bug\uff0c\u800c\u662f V8 \u7684\u4e00\u4e2a\u7279\u522b\u7684\u7279\u6027\u3002\u4e5f\u8bb8\u4ee5\u540e\u4f1a\u88ab\u4fee\u6539\u3002\u4f60\u59cb\u7ec8\u53ef\u4ee5\u901a\u8fc7\u8fd0\u884c\u672c\u6587\u4e2d\u7684\u793a\u4f8b\u6765\u8fdb\u884c\u68c0\u67e5\u3002<\/p>\n<h1>\u8001\u65e7\u7684 var<\/h1>\n<blockquote>\n<p>\u672c\u6587\u7528\u4e8e\u5e2e\u52a9\u7406\u89e3\u65e7\u811a\u672c<br \/>\n\u672c\u6587\u6240\u8bb2\u7684\u5185\u5bb9\u5bf9\u4e8e\u5e2e\u52a9\u7406\u89e3\u65e7\u811a\u672c\u5f88\u6709\u7528\u3002<br \/>\n\u4f46\u8fd9\u4e0d\u662f\u6211\u4eec\u7f16\u5199\u65b0\u4ee3\u7801\u7684\u65b9\u5f0f\u3002<\/p>\n<\/blockquote>\n<p><code>var<\/code>\u00a0\u58f0\u660e\u4e0e\u00a0<code>let<\/code>\u00a0\u76f8\u4f3c\u3002\u5927\u90e8\u5206\u60c5\u51b5\u4e0b\uff0c\u6211\u4eec\u53ef\u4ee5\u7528\u00a0<code>let<\/code>\u00a0\u4ee3\u66ff\u00a0<code>var<\/code>\u00a0\u6216\u8005\u00a0<code>var<\/code>\u00a0\u4ee3\u66ff\u00a0<code>let<\/code>\uff0c\u90fd\u80fd\u8fbe\u5230\u9884\u671f\u7684\u6548\u679c<br \/>\n\u4f46\u5b9e\u9645\u4e0a\u00a0<code>var<\/code>\u00a0\u5374\u662f\u4e00\u5934\u975e\u5e38\u4e0d\u540c\u7684\uff0c\u6e90\u81ea\u8fdc\u53e4\u65f6\u4ee3\u7684\u602a\u517d\u3002\u5728\u73b0\u4ee3\u811a\u672c\u4e2d\u4e00\u822c\u4e0d\u518d\u4f7f\u7528\u5b83\uff0c\u4f46\u5b83\u4ecd\u7136\u6f5c\u4f0f\u5728\u65e7\u811a\u672c\u4e2d\u3002<\/p>\n<h2>var \u6ca1\u6709\u5757\u7ea7\u4f5c\u7528\u57df<\/h2>\n<p>\u7528\u00a0<code>var<\/code>\u00a0\u58f0\u660e\u7684\u53d8\u91cf\uff0c\u4e0d\u662f\u51fd\u6570\u4f5c\u7528\u57df\u5c31\u662f\u5168\u5c40\u4f5c\u7528\u57df\u3002\u5b83\u4eec\u5728\u4ee3\u7801\u5757\u5916\u4e5f\u662f\u53ef\u89c1\u7684\uff08\u8bd1\u6ce8\uff1a\u4e5f\u5c31\u662f\u8bf4\uff0c<code>var<\/code>\u00a0\u58f0\u660e\u7684\u53d8\u91cf\u53ea\u6709\u51fd\u6570\u4f5c\u7528\u57df\u548c\u5168\u5c40\u4f5c\u7528\u57df\uff0c\u6ca1\u6709\u5757\u7ea7\u4f5c\u7528\u57df\uff09\u3002<\/p>\n<pre><code class=\"language-js\">if (true) {\n  var test = true; \/\/ \u4f7f\u7528 &quot;var&quot; \u800c\u4e0d\u662f &quot;let&quot;\n}\n\nalert(test); \/\/ true\uff0c\u53d8\u91cf\u5728 if \u7ed3\u675f\u540e\u4ecd\u5b58\u5728\n<\/code><\/pre>\n<p>\u7531\u4e8e\u00a0<code>var<\/code>\u00a0\u4f1a\u5ffd\u7565\u4ee3\u7801\u5757\uff0c\u56e0\u6b64\u6211\u4eec\u6709\u4e86\u4e00\u4e2a\u5168\u5c40\u53d8\u91cf\u00a0<code>test<\/code>\u3002<br \/>\n\u5bf9\u4e8e\u5faa\u73af\u4e5f\u662f\u8fd9\u6837\u7684\uff0c<code>var<\/code>\u00a0\u58f0\u660e\u7684\u53d8\u91cf\u6ca1\u6709\u5757\u7ea7\u4f5c\u7528\u57df\u4e5f\u6ca1\u6709\u5faa\u73af\u5c40\u90e8\u4f5c\u7528\u57df<br \/>\n\u5982\u679c\u4e00\u4e2a\u4ee3\u7801\u5757\u4f4d\u4e8e\u51fd\u6570\u5185\u90e8\uff0c\u90a3\u4e48\u00a0<code>var<\/code>\u00a0\u58f0\u660e\u7684\u53d8\u91cf\u7684\u4f5c\u7528\u57df\u5c06\u4e3a\u51fd\u6570\u4f5c\u7528\u57df<br \/>\n\u53ef\u4ee5\u770b\u5230\uff0c<code>var<\/code>\u00a0\u7a7f\u900f\u4e86\u00a0<code>if<\/code>\uff0c<code>for<\/code>\u00a0\u548c\u5176\u5b83\u4ee3\u7801\u5757\u3002\u8fd9\u662f\u56e0\u4e3a\u5728\u65e9\u671f\u7684 JavaScript \u4e2d\uff0c\u5757\u6ca1\u6709\u8bcd\u6cd5\u73af\u5883\uff0c\u800c\u00a0<code>var<\/code>\u00a0\u5c31\u662f\u8fd9\u4e2a\u65f6\u671f\u7684\u4ee3\u8868\u4e4b\u4e00\u3002<\/p>\n<h2>var \u5141\u8bb8\u91cd\u65b0\u58f0\u660e<\/h2>\n<p>\u4f7f\u7528\u00a0<code>var<\/code>\uff0c\u6211\u4eec\u53ef\u4ee5\u91cd\u590d\u58f0\u660e\u4e00\u4e2a\u53d8\u91cf\uff0c\u4e0d\u7ba1\u591a\u5c11\u6b21\u90fd\u884c\u3002\u5982\u679c\u6211\u4eec\u5bf9\u4e00\u4e2a\u5df2\u7ecf\u58f0\u660e\u7684\u53d8\u91cf\u4f7f\u7528\u00a0<code>var<\/code>\uff0c\u8fd9\u6761\u65b0\u7684\u58f0\u660e\u8bed\u53e5\u4f1a\u88ab\u5ffd\u7565<\/p>\n<h2>var \u58f0\u660e\u7684\u53d8\u91cf\uff0c\u53ef\u4ee5\u5728\u5176\u58f0\u660e\u8bed\u53e5\u524d\u5c31\u88ab\u4f7f\u7528<\/h2>\n<p>\u5f53\u51fd\u6570\u5f00\u59cb\u7684\u65f6\u5019\uff0c\u5c31\u4f1a\u5904\u7406\u00a0<code>var<\/code>\u00a0\u58f0\u660e\uff08\u811a\u672c\u542f\u52a8\u5bf9\u5e94\u5168\u5c40\u53d8\u91cf\uff09\u3002<br \/>\n\u6362\u8a00\u4e4b\uff0c<code>var<\/code>\u00a0\u58f0\u660e\u7684\u53d8\u91cf\u4f1a\u5728\u51fd\u6570\u5f00\u5934\u88ab\u5b9a\u4e49\uff0c\u4e0e\u5b83\u5728\u4ee3\u7801\u4e2d\u5b9a\u4e49\u7684\u4f4d\u7f6e\u65e0\u5173\uff08\u8fd9\u91cc\u4e0d\u8003\u8651\u5b9a\u4e49\u5728\u5d4c\u5957\u51fd\u6570\u4e2d\u7684\u60c5\u51b5\uff09\u3002<br \/>\n\u2026\u2026\u751a\u81f3\u4e0e\u8fd9\u79cd\u60c5\u51b5\u4e5f\u4e00\u6837\uff08\u8bb0\u4f4f\uff0c\u4ee3\u7801\u5757\u662f\u4f1a\u88ab\u5ffd\u7565\u7684\uff09<\/p>\n<pre><code class=\"language-js\">function sayHi() {\n  phrase = &quot;Hello&quot;; \/\/ (*)\n\n  if (false) {\n    var phrase;\n  }\n\n  alert(phrase);\n}\nsayHi();\n<\/code><\/pre>\n<p>\u4eba\u4eec\u5c06\u8fd9\u79cd\u884c\u4e3a\u79f0\u4e3a\u201c\u63d0\u5347\u201d\uff08\u82f1\u6587\u4e3a \u201choisting\u201d \u6216 \u201craising\u201d\uff09\uff0c\u56e0\u4e3a\u6240\u6709\u7684\u00a0<code>var<\/code>\u00a0\u90fd\u88ab\u201c\u63d0\u5347\u201d\u5230\u4e86\u51fd\u6570\u7684\u9876\u90e8\u3002<br \/>\n\u6240\u4ee5\uff0c\u5728\u4e0a\u9762\u7684\u4f8b\u5b50\u4e2d\uff0c<code>if (false)<\/code>\u00a0\u5206\u652f\u6c38\u8fdc\u90fd\u4e0d\u4f1a\u6267\u884c\uff0c\u4f46\u6ca1\u5173\u7cfb\uff0c\u5b83\u91cc\u9762\u7684\u00a0<code>var<\/code>\u00a0\u5728\u51fd\u6570\u521a\u5f00\u59cb\u65f6\u5c31\u88ab\u5904\u7406\u4e86\uff0c\u6240\u4ee5\u5728\u6267\u884c\u00a0<code>(*)<\/code>\u00a0\u90a3\u884c\u4ee3\u7801\u65f6\uff0c\u53d8\u91cf\u662f\u5b58\u5728\u7684\u3002<br \/>\n<strong>\u58f0\u660e\u4f1a\u88ab\u63d0\u5347\uff0c\u4f46\u662f\u8d4b\u503c\u4e0d\u4f1a\u3002<\/strong><br \/>\n<code>var phrase = &quot;Hello&quot;<\/code>\u00a0\u8fd9\u884c\u4ee3\u7801\u5305\u542b\u4e24\u4e2a\u884c\u4e3a\uff1a<\/p>\n<ol>\n<li>\u4f7f\u7528\u00a0<code>var<\/code>\u00a0\u58f0\u660e\u53d8\u91cf<\/li>\n<li>\u4f7f\u7528\u00a0<code>=<\/code>\u00a0\u7ed9\u53d8\u91cf\u8d4b\u503c\u3002<br \/>\n\u56e0\u4e3a\u6240\u6709\u7684\u00a0<code>var<\/code>\u00a0\u58f0\u660e\u90fd\u662f\u5728\u51fd\u6570\u5f00\u5934\u5904\u7406\u7684\uff0c\u6211\u4eec\u53ef\u4ee5\u5728\u4efb\u4f55\u5730\u65b9\u5f15\u7528\u5b83\u4eec\u3002\u4f46\u662f\u5728\u5b83\u4eec\u88ab\u8d4b\u503c\u4e4b\u524d\u90fd\u662f undefined\u3002<\/li>\n<\/ol>\n<h2>IIFE<\/h2>\n<p>\u5728\u4e4b\u524d\uff0cJavaScript \u4e2d\u53ea\u6709\u00a0<code>var<\/code>\u00a0\u8fd9\u4e00\u79cd\u58f0\u660e\u53d8\u91cf\u7684\u65b9\u5f0f\uff0c\u5e76\u4e14\u8fd9\u79cd\u65b9\u5f0f\u58f0\u660e\u7684\u53d8\u91cf\u6ca1\u6709\u5757\u7ea7\u4f5c\u7528\u57df\uff0c\u7a0b\u5e8f\u5458\u4eec\u5c31\u53d1\u660e\u4e86\u4e00\u79cd\u6a21\u4eff\u5757\u7ea7\u4f5c\u7528\u57df\u7684\u65b9\u6cd5\u3002\u8fd9\u79cd\u65b9\u6cd5\u88ab\u79f0\u4e3a\u201c\u7acb\u5373\u8c03\u7528\u51fd\u6570\u8868\u8fbe\u5f0f\u201d\uff08immediately-invoked function expressions\uff0cIIFE\uff09\u3002<br \/>\n\u5982\u4eca\uff0c\u6211\u4eec\u4e0d\u5e94\u8be5\u518d\u4f7f\u7528 IIFE \u4e86\uff0c\u4f46\u662f\u4f60\u53ef\u4ee5\u5728\u65e7\u811a\u672c\u4e2d\u627e\u5230\u5b83\u4eec\u3002<\/p>\n<pre><code class=\"language-js\">(function() {\n  var message = &quot;Hello&quot;;\n  alert(message); \/\/ Hello\n})();\n<\/code><\/pre>\n<p>\u8fd9\u91cc\uff0c\u521b\u5efa\u4e86\u4e00\u4e2a\u51fd\u6570\u8868\u8fbe\u5f0f\u5e76\u7acb\u5373\u8c03\u7528\u3002\u56e0\u6b64\uff0c\u4ee3\u7801\u7acb\u5373\u6267\u884c\u5e76\u62e5\u6709\u4e86\u81ea\u5df1\u7684\u79c1\u6709\u53d8\u91cf\u3002<br \/>\n\u51fd\u6570\u8868\u8fbe\u5f0f\u88ab\u62ec\u53f7\u00a0<code>(function {...})<\/code>\u00a0\u5305\u88f9\u8d77\u6765\uff0c\u56e0\u4e3a\u5f53 JavaScript \u5f15\u64ce\u5728\u4e3b\u4ee3\u7801\u4e2d\u9047\u5230\u00a0<code>&quot;function&quot;<\/code>\u00a0\u65f6\uff0c\u5b83\u4f1a\u628a\u5b83\u5f53\u6210\u4e00\u4e2a\u51fd\u6570\u58f0\u660e\u7684\u5f00\u59cb\u3002\u4f46\u51fd\u6570\u58f0\u660e\u5fc5\u987b\u6709\u4e00\u4e2a\u51fd\u6570\u540d,\u5373\u4f7f\u6211\u4eec\u8bf4\uff1a\u201c\u597d\u5427\uff0c\u90a3\u6211\u4eec\u52a0\u4e00\u4e2a\u540d\u79f0\u5427\u201d\uff0c\u4f46\u5b83\u4ecd\u7136\u4e0d\u5de5\u4f5c\uff0c\u56e0\u4e3a JavaScript \u4e0d\u5141\u8bb8\u7acb\u5373\u8c03\u7528\u51fd\u6570\u58f0\u660e\uff1a<\/p>\n<pre><code class=\"language-js\">\/\/ \u4e0b\u9762\u7684\u62ec\u53f7\u4f1a\u5bfc\u81f4\u8bed\u6cd5\u9519\u8bef\nfunction go() {\n\n}(); \/\/ &lt;-- \u4e0d\u80fd\u7acb\u5373\u8c03\u7528\u51fd\u6570\u58f0\u660e\n<\/code><\/pre>\n<p>\u56e0\u6b64\uff0c\u9700\u8981\u4f7f\u7528\u5706\u62ec\u53f7\u628a\u8be5\u51fd\u6570\u8868\u8fbe\u5f0f\u5305\u8d77\u6765\uff0c\u4ee5\u544a\u8bc9 JavaScript\uff0c\u8fd9\u4e2a\u51fd\u6570\u662f\u5728\u53e6\u4e00\u4e2a\u8868\u8fbe\u5f0f\u7684\u4e0a\u4e0b\u6587\u4e2d\u521b\u5efa\u7684\uff0c\u56e0\u6b64\u5b83\u662f\u4e00\u4e2a\u51fd\u6570\u8868\u8fbe\u5f0f\uff1a\u5b83\u4e0d\u9700\u8981\u51fd\u6570\u540d\uff0c\u53ef\u4ee5\u7acb\u5373\u8c03\u7528\u3002<\/p>\n<pre><code class=\"language-js\">\/\/ \u521b\u5efa IIFE \u7684\u65b9\u6cd5\n\n(function() {\n  alert(&quot;Parentheses around the function&quot;);\n})();\n\n(function() {\n  alert(&quot;Parentheses around the whole thing&quot;);\n}());\n\n!function() {\n  alert(&quot;Bitwise NOT operator starts the expression&quot;);\n}();\n\n+function() {\n  alert(&quot;Unary plus starts the expression&quot;);\n}();\n<\/code><\/pre>\n<p>\u5728\u4e0a\u9762\u7684\u6240\u6709\u60c5\u51b5\u4e2d\uff0c\u6211\u4eec\u90fd\u58f0\u660e\u4e86\u4e00\u4e2a\u51fd\u6570\u8868\u8fbe\u5f0f\u5e76\u7acb\u5373\u8fd0\u884c\u5b83\u3002\u8bf7\u518d\u6ce8\u610f\u4e00\u4e0b\uff1a\u5982\u4eca\u6211\u4eec\u6ca1\u6709\u7406\u7531\u6765\u7f16\u5199\u8fd9\u6837\u7684\u4ee3\u7801\u3002<\/p>\n<h1>\u5168\u5c40\u5bf9\u8c61<\/h1>\n<p>\u5168\u5c40\u5bf9\u8c61\u63d0\u4f9b\u53ef\u5728\u4efb\u4f55\u5730\u65b9\u4f7f\u7528\u7684\u53d8\u91cf\u548c\u51fd\u6570\u3002\u9ed8\u8ba4\u60c5\u51b5\u4e0b\uff0c\u8fd9\u4e9b\u5168\u5c40\u53d8\u91cf\u5185\u5efa\u4e8e\u8bed\u8a00\u6216\u73af\u5883\u4e2d\u3002<br \/>\n\u5728\u6d4f\u89c8\u5668\u4e2d\uff0c\u5b83\u7684\u540d\u5b57\u662f \u201cwindow\u201d\uff0c\u5bf9 Node.js \u800c\u8a00\uff0c\u5b83\u7684\u540d\u5b57\u662f \u201cglobal\u201d\uff0c\u5176\u5b83\u73af\u5883\u53ef\u80fd\u7528\u7684\u662f\u522b\u7684\u540d\u5b57\u3002<br \/>\n\u6700\u8fd1\uff0c<code>globalThis<\/code>\u00a0\u88ab\u4f5c\u4e3a\u5168\u5c40\u5bf9\u8c61\u7684\u6807\u51c6\u540d\u79f0\u52a0\u5165\u5230\u4e86 JavaScript \u4e2d\uff0c\u6240\u6709\u73af\u5883\u90fd\u5e94\u8be5\u652f\u6301\u8be5\u540d\u79f0\u3002\u6240\u6709\u4e3b\u6d41\u6d4f\u89c8\u5668\u90fd\u652f\u6301\u5b83\u3002<br \/>\n\u5047\u8bbe\u6211\u4eec\u7684\u73af\u5883\u662f\u6d4f\u89c8\u5668\uff0c\u6211\u4eec\u5c06\u5728\u8fd9\u513f\u4f7f\u7528 \u201cwindow\u201d\u3002\u5982\u679c\u4f60\u7684\u811a\u672c\u53ef\u80fd\u4f1a\u7528\u6765\u5728\u5176\u4ed6\u73af\u5883\u4e2d\u8fd0\u884c\uff0c\u5219\u6700\u597d\u4f7f\u7528\u00a0<code>globalThis<\/code>\u3002<br \/>\n\u5168\u5c40\u5bf9\u8c61\u7684\u6240\u6709\u5c5e\u6027\u90fd\u53ef\u4ee5\u88ab\u76f4\u63a5\u8bbf\u95ee<\/p>\n<pre><code class=\"language-js\">alert(&quot;Hello&quot;);\n\/\/ \u7b49\u540c\u4e8e\nwindow.alert(&quot;Hello&quot;);\n<\/code><\/pre>\n<p>\u5728\u6d4f\u89c8\u5668\u4e2d\uff0c\u4f7f\u7528\u00a0<code>var<\/code>\uff08\u800c\u4e0d\u662f\u00a0<code>let\/const<\/code>\uff01\uff09\u58f0\u660e\u7684\u5168\u5c40\u51fd\u6570\u548c\u53d8\u91cf\u4f1a\u6210\u4e3a\u5168\u5c40\u5bf9\u8c61\u7684\u5c5e\u6027\u3002<br \/>\n\u51fd\u6570\u58f0\u660e\uff08\u7279\u6307\u5728\u4e3b\u4ee3\u7801\u6d41\u4e2d\u5177\u6709\u00a0<code>function<\/code>\u00a0\u5173\u952e\u5b57\u7684\u8bed\u53e5\uff0c\u800c\u4e0d\u662f\u51fd\u6570\u8868\u8fbe\u5f0f\uff09\u4e5f\u6709\u8fd9\u6837\u7684\u6548\u679c\u3002<br \/>\n\u8bf7\u4e0d\u8981\u4f9d\u8d56\u5b83\uff01\u8fd9\u79cd\u884c\u4e3a\u662f\u51fa\u4e8e\u517c\u5bb9\u6027\u800c\u5b58\u5728\u7684\u3002\u73b0\u4ee3\u811a\u672c\u4f7f\u7528\u00a0<a href=\"https:\/\/zh.javascript.info\/modules\">JavaScript modules<\/a>\u00a0\u6240\u4ee5\u4e0d\u4f1a\u53d1\u751f\u8fd9\u79cd\u4e8b\u60c5\u3002<br \/>\n\u5982\u679c\u4e00\u4e2a\u503c\u975e\u5e38\u91cd\u8981\uff0c\u4ee5\u81f3\u4e8e\u4f60\u60f3\u4f7f\u5b83\u5728\u5168\u5c40\u8303\u56f4\u5185\u53ef\u7528\uff0c\u90a3\u4e48\u53ef\u4ee5\u76f4\u63a5\u5c06\u5176\u4f5c\u4e3a\u5c5e\u6027\u5199\u5165<\/p>\n<pre><code class=\"language-js\">\/\/ \u5c06\u5f53\u524d\u7528\u6237\u4fe1\u606f\u5168\u5c40\u5316\uff0c\u4ee5\u5141\u8bb8\u6240\u6709\u811a\u672c\u8bbf\u95ee\u5b83\nwindow.currentUser = {\n  name: &quot;John&quot;\n};\n\n\/\/ \u4ee3\u7801\u4e2d\u7684\u53e6\u4e00\u4e2a\u4f4d\u7f6e\nalert(currentUser.name);  \/\/ John\n\n\/\/ \u6216\u8005\uff0c\u5982\u679c\u6211\u4eec\u6709\u4e00\u4e2a\u540d\u4e3a &quot;currentUser&quot; \u7684\u5c40\u90e8\u53d8\u91cf\n\/\/ \u4ece window \u663e\u5f0f\u5730\u83b7\u53d6\u5b83\uff08\u8fd9\u662f\u5b89\u5168\u7684\uff01\uff09\nalert(window.currentUser.name); \/\/ John\n<\/code><\/pre>\n<p>\u4e5f\u5c31\u662f\u8bf4\uff0c\u4e00\u822c\u4e0d\u5efa\u8bae\u4f7f\u7528\u5168\u5c40\u53d8\u91cf\u3002\u5168\u5c40\u53d8\u91cf\u5e94\u5c3d\u53ef\u80fd\u7684\u5c11\u3002\u4e0e\u4f7f\u7528\u5916\u90e8\u53d8\u91cf\u6216\u5168\u5c40\u53d8\u91cf\u76f8\u6bd4\uff0c\u51fd\u6570\u83b7\u53d6\u201c\u8f93\u5165\u201d\u53d8\u91cf\u5e76\u4ea7\u751f\u7279\u5b9a\u201c\u8f93\u51fa\u201d\u7684\u4ee3\u7801\u8bbe\u8ba1\u66f4\u52a0\u6e05\u6670\uff0c\u4e0d\u6613\u51fa\u9519\u4e14\u66f4\u6613\u4e8e\u6d4b\u8bd5\u3002<\/p>\n<h2>\u4f7f\u7528 polyfills<\/h2>\n<p>\u6211\u4eec\u4f7f\u7528\u5168\u5c40\u5bf9\u8c61\u6765\u6d4b\u8bd5\u5bf9\u73b0\u4ee3\u8bed\u8a00\u529f\u80fd\u7684\u652f\u6301\u3002<br \/>\n\u4f8b\u5982\uff0c\u6d4b\u8bd5\u662f\u5426\u5b58\u5728\u5185\u5efa\u7684\u00a0<code>Promise<\/code>\u00a0\u5bf9\u8c61\uff08\u5728\u7248\u672c\u7279\u522b\u65e7\u7684\u6d4f\u89c8\u5668\u4e2d\u4e0d\u5b58\u5728\uff09<br \/>\n\u5982\u679c\u6ca1\u6709\uff08\u4f8b\u5982\uff0c\u6211\u4eec\u4f7f\u7528\u7684\u662f\u65e7\u7248\u6d4f\u89c8\u5668\uff09\uff0c\u90a3\u4e48\u6211\u4eec\u53ef\u4ee5\u521b\u5efa \u201cpolyfills\u201d\uff1a\u6dfb\u52a0\u73af\u5883\u4e0d\u652f\u6301\u4f46\u5728\u73b0\u4ee3\u6807\u51c6\u4e2d\u5b58\u5728\u7684\u529f\u80fd\u3002<\/p>\n<h1>\u51fd\u6570\u5bf9\u8c61 NFE<\/h1>\n<p>\u6211\u4eec\u5df2\u7ecf\u77e5\u9053\uff0c\u5728 JavaScript \u4e2d\uff0c\u51fd\u6570\u4e5f\u662f\u4e00\u4e2a\u503c\u3002<br \/>\n\u800c JavaScript \u4e2d\u7684\u6bcf\u4e2a\u503c\u90fd\u6709\u4e00\u79cd\u7c7b\u578b\uff0c\u90a3\u4e48\u51fd\u6570\u662f\u4ec0\u4e48\u7c7b\u578b\u5462\uff1f<br \/>\n\u5728 JavaScript \u4e2d\uff0c\u51fd\u6570\u7684\u7c7b\u578b\u662f\u5bf9\u8c61\u3002<br \/>\n\u4e00\u4e2a\u5bb9\u6613\u7406\u89e3\u7684\u65b9\u5f0f\u662f\u628a\u51fd\u6570\u60f3\u8c61\u6210\u53ef\u88ab\u8c03\u7528\u7684\u201c\u884c\u4e3a\u5bf9\u8c61\uff08action object\uff09\u201d\u3002\u6211\u4eec\u4e0d\u4ec5\u53ef\u4ee5\u8c03\u7528\u5b83\u4eec\uff0c\u8fd8\u80fd\u628a\u5b83\u4eec\u5f53\u4f5c\u5bf9\u8c61\u6765\u5904\u7406\uff1a\u589e\/\u5220\u5c5e\u6027\uff0c\u6309\u5f15\u7528\u4f20\u9012\u7b49\u3002<\/p>\n<h2>\u5c5e\u6027 name<\/h2>\n<p>\u51fd\u6570\u5bf9\u8c61\u5305\u542b\u4e00\u4e9b\u4fbf\u4e8e\u4f7f\u7528\u7684\u5c5e\u6027\u3002<br \/>\n\u6bd4\u5982\uff0c\u4e00\u4e2a\u51fd\u6570\u7684\u540d\u5b57\u53ef\u4ee5\u901a\u8fc7\u5c5e\u6027 \u201cname\u201d \u6765\u8bbf\u95ee<br \/>\n\u66f4\u6709\u8da3\u7684\u662f\uff0c\u540d\u79f0\u8d4b\u503c\u7684\u903b\u8f91\u5f88\u667a\u80fd\u3002\u5373\u4f7f\u51fd\u6570\u88ab\u521b\u5efa\u65f6\u6ca1\u6709\u540d\u5b57\uff0c\u540d\u79f0\u8d4b\u503c\u7684\u903b\u8f91\u4e5f\u80fd\u7ed9\u5b83\u8d4b\u4e88\u4e00\u4e2a\u6b63\u786e\u7684\u540d\u5b57\uff0c\u7136\u540e\u8fdb\u884c\u8d4b\u503c<br \/>\n\u5f53\u4ee5\u9ed8\u8ba4\u503c\u7684\u65b9\u5f0f\u5b8c\u6210\u4e86\u8d4b\u503c\u65f6\uff0c\u5b83\u4e5f\u6709\u6548<\/p>\n<pre><code class=\"language-js\">function f(sayHi = function() {}) {\n  alert(sayHi.name); \/\/ sayHi\uff08\u751f\u6548\u4e86\uff01\uff09\n}\n\nf();\n<\/code><\/pre>\n<p>\u89c4\u8303\u4e2d\u628a\u8fd9\u79cd\u7279\u6027\u53eb\u505a\u300c\u4e0a\u4e0b\u6587\u547d\u540d\u300d\u3002\u5982\u679c\u51fd\u6570\u81ea\u5df1\u6ca1\u6709\u63d0\u4f9b\uff0c\u90a3\u4e48\u5728\u8d4b\u503c\u4e2d\uff0c\u4f1a\u6839\u636e\u4e0a\u4e0b\u6587\u6765\u63a8\u6d4b\u4e00\u4e2a\u3002<br \/>\n\u8fd9\u6ca1\u6709\u4ec0\u4e48\u795e\u5947\u7684\u3002\u6709\u65f6\u4f1a\u51fa\u73b0\u65e0\u6cd5\u63a8\u6d4b\u540d\u5b57\u7684\u60c5\u51b5\u3002\u6b64\u65f6\uff0c\u5c5e\u6027\u00a0<code>name<\/code>\u00a0\u4f1a\u662f\u7a7a\uff0c\u50cf\u8fd9\u6837<\/p>\n<pre><code class=\"language-js\">\/\/ \u51fd\u6570\u662f\u5728\u6570\u7ec4\u4e2d\u521b\u5efa\u7684\nlet arr = [function() {}];\n\nalert( arr[0].name ); \/\/ &lt;\u7a7a\u5b57\u7b26\u4e32&gt;\n\/\/ \u5f15\u64ce\u65e0\u6cd5\u8bbe\u7f6e\u6b63\u786e\u7684\u540d\u5b57\uff0c\u6240\u4ee5\u6ca1\u6709\u503c\n<\/code><\/pre>\n<h2>\u5c5e\u6027 length<\/h2>\n<p>\u8fd8\u6709\u53e6\u4e00\u4e2a\u5185\u5efa\u5c5e\u6027 \u201clength\u201d\uff0c\u5b83\u8fd4\u56de\u51fd\u6570\u5165\u53c2\u7684\u4e2a\u6570<\/p>\n<p>rest \u53c2\u6570\u4e0d\u53c2\u4e0e\u8ba1\u6570\u3002<br \/>\n\u5c5e\u6027\u00a0<code>length<\/code>\u00a0\u6709\u65f6\u5728\u64cd\u4f5c\u5176\u5b83\u51fd\u6570\u7684\u51fd\u6570\u4e2d\u7528\u4e8e\u505a\u00a0<a href=\"https:\/\/zh.wikipedia.org\/wiki\/%E5%86%85%E7%9C%81_(%E8%AE%A1%E7%AE%97%E6%9C%BA%E7%A7%91%E5%AD%A6)\">\u5185\u7701\/\u8fd0\u884c\u65f6\u68c0\u67e5\uff08introspection\uff09<\/a>\u3002<br \/>\n\u6bd4\u5982\uff0c\u4e0b\u9762\u7684\u4ee3\u7801\u4e2d\u51fd\u6570\u00a0<code>ask<\/code>\u00a0\u63a5\u53d7\u4e00\u4e2a\u8be2\u95ee\u7b54\u6848\u7684\u53c2\u6570\u00a0<code>question<\/code>\u00a0\u548c\u53ef\u80fd\u5305\u542b\u4efb\u610f\u6570\u91cf\u00a0<code>handler<\/code>\u00a0\u7684\u53c2\u6570\u00a0<code>...handlers<\/code>\u3002<br \/>\n\u5f53\u7528\u6237\u63d0\u4f9b\u4e86\u81ea\u5df1\u7684\u7b54\u6848\u540e\uff0c\u51fd\u6570\u4f1a\u8c03\u7528\u90a3\u4e9b\u00a0<code>handlers<\/code>\u3002\u6211\u4eec\u53ef\u4ee5\u4f20\u5165\u4e24\u79cd\u00a0<code>handlers<\/code>\uff1a<\/p>\n<ul>\n<li>\u4e00\u79cd\u662f\u65e0\u53c2\u51fd\u6570\uff0c\u5b83\u4ec5\u5728\u7528\u6237\u7ed9\u51fa\u80af\u5b9a\u56de\u7b54\u65f6\u88ab\u8c03\u7528\u3002<\/li>\n<li>\u4e00\u79cd\u662f\u6709\u53c2\u51fd\u6570\uff0c\u5b83\u5728\u4e24\u79cd\u60c5\u51b5\u90fd\u4f1a\u88ab\u8c03\u7528\uff0c\u5e76\u4e14\u8fd4\u56de\u4e00\u4e2a\u7b54\u6848\u3002<br \/>\n\u4e3a\u4e86\u6b63\u786e\u5730\u8c03\u7528\u00a0<code>handler<\/code>\uff0c\u6211\u4eec\u9700\u8981\u68c0\u67e5\u00a0<code>handler.length<\/code>\u00a0\u5c5e\u6027\u3002<br \/>\n\u6211\u4eec\u7684\u60f3\u6cd5\u662f\uff0c\u6211\u4eec\u7528\u4e00\u4e2a\u7b80\u5355\u7684\u65e0\u53c2\u6570\u7684\u00a0<code>handler<\/code>\u00a0\u8bed\u6cd5\u6765\u5904\u7406\u79ef\u6781\u7684\u56de\u7b54\uff08\u6700\u5e38\u89c1\u7684\u53d8\u4f53\uff09\uff0c\u4f46\u4e5f\u8981\u80fd\u591f\u63d0\u4f9b\u901a\u7528\u7684 handler<br \/>\n\u8fd9\u5c31\u662f\u6240\u8c13\u7684\u00a0<a href=\"https:\/\/en.wikipedia.org\/wiki\/Polymorphism_(computer_science)\">\u591a\u6001\u6027<\/a>\u00a0\u7684\u4e00\u4e2a\u4f8b\u5b50 \u2014\u2014 \u6839\u636e\u53c2\u6570\u7684\u7c7b\u578b\uff0c\u6216\u8005\u6839\u636e\u5728\u6211\u4eec\u7684\u5177\u4f53\u60c5\u666f\u4e0b\u7684\u00a0<code>length<\/code>\u00a0\u6765\u505a\u4e0d\u540c\u7684\u5904\u7406\u3002\u8fd9\u79cd\u601d\u60f3\u5728 JavaScript \u7684\u5e93\u91cc\u6709\u5e94\u7528\u3002<\/li>\n<\/ul>\n<h2>\u81ea\u5b9a\u4e49\u5c5e\u6027<\/h2>\n<p>\u6211\u4eec\u4e5f\u53ef\u4ee5\u6dfb\u52a0\u6211\u4eec\u81ea\u5df1\u7684\u5c5e\u6027\u3002<\/p>\n<blockquote>\n<p>\u5c5e\u6027\u4e0d\u662f\u53d8\u91cf<br \/>\n\u88ab\u8d4b\u503c\u7ed9\u51fd\u6570\u7684\u5c5e\u6027\uff0c\u6bd4\u5982\u00a0<code>sayHi.counter = 0<\/code>\uff0c<strong>\u4e0d\u4f1a<\/strong>\u00a0\u5728\u51fd\u6570\u5185\u5b9a\u4e49\u4e00\u4e2a\u5c40\u90e8\u53d8\u91cf\u00a0<code>counter<\/code>\u3002\u6362\u53e5\u8bdd\u8bf4\uff0c\u5c5e\u6027\u00a0<code>counter<\/code>\u00a0\u548c\u53d8\u91cf\u00a0<code>let counter<\/code>\u00a0\u662f\u6beb\u4e0d\u76f8\u5173\u7684\u4e24\u4e2a\u4e1c\u897f\u3002<br \/>\n\u6211\u4eec\u53ef\u4ee5\u628a\u51fd\u6570\u5f53\u4f5c\u5bf9\u8c61\uff0c\u5728\u5b83\u91cc\u9762\u5b58\u50a8\u5c5e\u6027\uff0c\u4f46\u662f\u8fd9\u5bf9\u5b83\u7684\u6267\u884c\u6ca1\u6709\u4efb\u4f55\u5f71\u54cd\u3002\u53d8\u91cf\u4e0d\u662f\u51fd\u6570\u5c5e\u6027\uff0c\u53cd\u4e4b\u4ea6\u7136\u3002\u5b83\u4eec\u4e4b\u95f4\u662f\u5e73\u884c\u7684\u3002<\/p>\n<\/blockquote>\n<p>\u51fd\u6570\u5c5e\u6027\u6709\u65f6\u4f1a\u7528\u6765\u66ff\u4ee3\u95ed\u5305\u3002<br \/>\n\u90a3\u4e48\u5b83\u548c\u95ed\u5305\u8c01\u597d\u8c01\u8d56\uff1f<br \/>\n\u4e24\u8005\u6700\u5927\u7684\u4e0d\u540c\u5c31\u662f\u5982\u679c\u00a0<code>count<\/code>\u00a0\u7684\u503c\u4f4d\u4e8e\u5916\u5c42\uff08\u51fd\u6570\uff09\u53d8\u91cf\u4e2d\uff0c\u90a3\u4e48\u5916\u90e8\u7684\u4ee3\u7801\u65e0\u6cd5\u8bbf\u95ee\u5230\u5b83\uff0c\u53ea\u6709\u5d4c\u5957\u7684\u90a3\u4e9b\u51fd\u6570\u53ef\u4ee5\u4fee\u6539\u5b83\u3002\u800c\u5982\u679c\u5b83\u662f\u7ed1\u5b9a\u5230\u51fd\u6570\u7684\uff0c\u90a3\u4e48\u5c31\u53ef\u4ee5\u8fd9\u6837<\/p>\n<pre><code class=\"language-js\">function makeCounter() {\n\n  function counter() {\n    return counter.count++;\n  };\n\n  counter.count = 0;\n\n  return counter;\n}\n\nlet counter = makeCounter();\n\ncounter.count = 10;\nalert( counter() ); \/\/ 10\n<\/code><\/pre>\n<h2>\u547d\u540d\u51fd\u6570\u8868\u8fbe\u5f0f<\/h2>\n<p>\u547d\u540d\u51fd\u6570\u8868\u8fbe\u5f0f\uff08NFE\uff0cNamed Function Expression\uff09\uff0c\u6307\u5e26\u6709\u540d\u5b57\u7684\u51fd\u6570\u8868\u8fbe\u5f0f\u7684\u672f\u8bed\u3002<\/p>\n<pre><code class=\"language-js\">let sayHi = function func(who) {\n  alert(`Hello, ${who}`);\n};\n<\/code><\/pre>\n<p>\u6211\u4eec\u8fd9\u91cc\u5f97\u5230\u4e86\u4ec0\u4e48\u5417\uff1f\u4e3a\u5b83\u6dfb\u52a0\u4e00\u4e2a\u00a0<code>&quot;func&quot;<\/code>\u00a0\u540d\u5b57\u7684\u76ee\u7684\u662f\u4ec0\u4e48\uff1f<br \/>\n\u9996\u5148\u8bf7\u6ce8\u610f\uff0c\u5b83\u4ecd\u7136\u662f\u4e00\u4e2a\u51fd\u6570\u8868\u8fbe\u5f0f\u3002\u5728\u00a0<code>function<\/code>\u00a0\u540e\u9762\u52a0\u4e00\u4e2a\u540d\u5b57\u00a0<code>&quot;func&quot;<\/code>\u00a0\u6ca1\u6709\u4f7f\u5b83\u6210\u4e3a\u4e00\u4e2a\u51fd\u6570\u58f0\u660e\uff0c\u56e0\u4e3a\u5b83\u4ecd\u7136\u662f\u4f5c\u4e3a\u8d4b\u503c\u8868\u8fbe\u5f0f\u4e2d\u7684\u4e00\u90e8\u5206\u88ab\u521b\u5efa\u7684\u3002<br \/>\n\u6dfb\u52a0\u8fd9\u4e2a\u540d\u5b57\u5f53\u7136\u4e5f\u6ca1\u6709\u6253\u7834\u4efb\u4f55\u4e1c\u897f\u3002<br \/>\n\u51fd\u6570\u4f9d\u7136\u53ef\u4ee5\u901a\u8fc7\u00a0<code>sayHi()<\/code>\u00a0\u6765\u8c03\u7528<br \/>\n\u5173\u4e8e\u540d\u5b57\u00a0<code>func<\/code>\u00a0\u6709\u4e24\u4e2a\u7279\u6b8a\u7684\u5730\u65b9\uff0c\u8fd9\u5c31\u662f\u6dfb\u52a0\u5b83\u7684\u539f\u56e0\uff1a<\/p>\n<ol>\n<li>\u5b83\u5141\u8bb8\u51fd\u6570\u5728\u5185\u90e8\u5f15\u7528\u81ea\u5df1\u3002<\/li>\n<li>\u5b83\u5728\u51fd\u6570\u5916\u662f\u4e0d\u53ef\u89c1\u7684\u3002<br \/>\n\u4f8b\u5982\uff0c\u4e0b\u9762\u7684\u51fd\u6570\u00a0<code>sayHi<\/code>\u00a0\u4f1a\u5728\u6ca1\u6709\u5165\u53c2\u00a0<code>who<\/code>\u00a0\u65f6\uff0c\u4ee5\u00a0<code>&quot;Guest&quot;<\/code>\u00a0\u4e3a\u5165\u53c2\u8c03\u7528\u81ea\u5df1<\/li>\n<\/ol>\n<pre><code class=\"language-js\">let sayHi = function func(who) {\n  if (who) {\n    alert(`Hello, ${who}`);\n  } else {\n    func(&quot;Guest&quot;); \/\/ \u4f7f\u7528 func \u518d\u6b21\u8c03\u7528\u51fd\u6570\u81ea\u8eab\n  }\n};\n\nsayHi(); \/\/ Hello, Guest\n\n\/\/ \u4f46\u8fd9\u4e0d\u5de5\u4f5c\uff1a\nfunc(); \/\/ Error, func is not defined\uff08\u5728\u51fd\u6570\u5916\u4e0d\u53ef\u89c1\uff09\n<\/code><\/pre>\n<p>\u6211\u4eec\u4e3a\u4ec0\u4e48\u4f7f\u7528\u00a0<code>func<\/code>\u00a0\u5462\uff1f\u4e3a\u4ec0\u4e48\u4e0d\u76f4\u63a5\u4f7f\u7528\u00a0<code>sayHi<\/code>\u00a0\u8fdb\u884c\u5d4c\u5957\u8c03\u7528\uff1f<br \/>\n\u95ee\u9898\u5728\u4e8e\u00a0<code>sayHi<\/code>\u00a0\u7684\u503c\u53ef\u80fd\u4f1a\u88ab\u51fd\u6570\u5916\u90e8\u7684\u4ee3\u7801\u6539\u53d8\u3002\u5982\u679c\u8be5\u51fd\u6570\u88ab\u8d4b\u503c\u7ed9\u53e6\u5916\u4e00\u4e2a\u53d8\u91cf\uff08\u8bd1\u6ce8\uff1a\u4e5f\u5c31\u662f\u539f\u53d8\u91cf\u88ab\u4fee\u6539\uff09\uff0c\u90a3\u4e48\u51fd\u6570\u5c31\u4f1a\u5f00\u59cb\u62a5\u9519<br \/>\n\u53d1\u751f\u8fd9\u79cd\u60c5\u51b5\u662f\u56e0\u4e3a\u8be5\u51fd\u6570\u4ece\u5b83\u7684\u5916\u90e8\u8bcd\u6cd5\u73af\u5883\u83b7\u53d6\u00a0<code>sayHi<\/code>\u3002\u6ca1\u6709\u5c40\u90e8\u7684\u00a0<code>sayHi<\/code>\u00a0\u4e86\uff0c\u6240\u4ee5\u4f7f\u7528\u5916\u90e8\u53d8\u91cf\u3002\u800c\u5f53\u8c03\u7528\u65f6\uff0c\u5916\u90e8\u7684\u00a0<code>sayHi<\/code>\u00a0\u662f\u00a0<code>null<\/code>\u3002<br \/>\n\u6211\u4eec\u7ed9\u51fd\u6570\u8868\u8fbe\u5f0f\u6dfb\u52a0\u7684\u53ef\u9009\u7684\u540d\u5b57\uff0c\u6b63\u662f\u7528\u6765\u89e3\u51b3\u8fd9\u7c7b\u95ee\u9898\u7684\u3002<\/p>\n<blockquote>\n<p>\u51fd\u6570\u58f0\u660e\u6ca1\u6709\u8fd9\u4e2a\u4e1c\u897f<br \/>\n\u8fd9\u91cc\u6240\u8bb2\u7684\u201c\u5185\u90e8\u540d\u201d\u7279\u6027\u53ea\u9488\u5bf9\u51fd\u6570\u8868\u8fbe\u5f0f\uff0c\u800c\u4e0d\u662f\u51fd\u6570\u58f0\u660e\u3002\u5bf9\u4e8e\u51fd\u6570\u58f0\u660e\uff0c\u6ca1\u6709\u7528\u6765\u6dfb\u52a0\u201c\u5185\u90e8\u201d\u540d\u7684\u8bed\u6cd5\u3002<br \/>\n\u6709\u65f6\uff0c\u5f53\u6211\u4eec\u9700\u8981\u4e00\u4e2a\u53ef\u9760\u7684\u5185\u90e8\u540d\u65f6\uff0c\u8fd9\u5c31\u6210\u4e3a\u4e86\u4f60\u628a\u51fd\u6570\u58f0\u660e\u91cd\u5199\u6210\u51fd\u6570\u8868\u8fbe\u5f0f\u7684\u7406\u7531\u4e86\u3002<\/p>\n<\/blockquote>\n<h1>new Funtion \u8bed\u6cd5<\/h1>\n<p>\u8fd8\u6709\u4e00\u79cd\u521b\u5efa\u51fd\u6570\u7684\u65b9\u6cd5\u3002\u5b83\u5f88\u5c11\u88ab\u4f7f\u7528\uff0c\u4f46\u6709\u4e9b\u65f6\u5019\u53ea\u80fd\u9009\u62e9\u5b83\u3002<\/p>\n<h2>\u8bed\u6cd5<\/h2>\n<pre><code class=\"language-js\">let func = new Function ([arg1, arg2, ...argN], functionBody);\n<\/code><\/pre>\n<p>\u8be5\u51fd\u6570\u662f\u901a\u8fc7\u4f7f\u7528\u53c2\u6570\u00a0<code>arg1...argN<\/code>\u00a0\u548c\u7ed9\u5b9a\u7684\u00a0<code>functionBody<\/code>\u00a0\u521b\u5efa\u7684\u3002<\/p>\n<pre><code class=\"language-js\">let sum = new Function('a', 'b', 'return a + b');\n\nalert( sum(1, 2) ); \/\/ 3\n<\/code><\/pre>\n<p>\u4e0e\u6211\u4eec\u5df2\u77e5\u7684\u5176\u4ed6\u65b9\u6cd5\u76f8\u6bd4\uff0c\u8fd9\u79cd\u65b9\u6cd5\u6700\u5927\u7684\u4e0d\u540c\u5728\u4e8e\uff0c\u5b83\u5b9e\u9645\u4e0a\u662f\u901a\u8fc7\u8fd0\u884c\u65f6\u901a\u8fc7\u53c2\u6570\u4f20\u9012\u8fc7\u6765\u7684\u5b57\u7b26\u4e32\u521b\u5efa\u7684\u3002<br \/>\n\u4ee5\u524d\u7684\u6240\u6709\u58f0\u660e\u65b9\u6cd5\u90fd\u9700\u8981\u6211\u4eec \u2014\u2014 \u7a0b\u5e8f\u5458\uff0c\u5728\u811a\u672c\u4e2d\u7f16\u5199\u51fd\u6570\u7684\u4ee3\u7801\u3002<br \/>\n\u4f46\u662f\u00a0<code>new Function<\/code>\u00a0\u5141\u8bb8\u6211\u4eec\u5c06\u4efb\u610f\u5b57\u7b26\u4e32\u53d8\u4e3a\u51fd\u6570\u3002\u4f8b\u5982\uff0c\u6211\u4eec\u53ef\u4ee5\u4ece\u670d\u52a1\u5668\u63a5\u6536\u4e00\u4e2a\u65b0\u7684\u51fd\u6570\u5e76\u6267\u884c\u5b83<\/p>\n<pre><code class=\"language-js\">let str = ... \u52a8\u6001\u5730\u63a5\u6536\u6765\u81ea\u670d\u52a1\u5668\u7684\u4ee3\u7801 ...\n\nlet func = new Function(str);\nfunc();\n<\/code><\/pre>\n<p>\u4f7f\u7528\u00a0<code>new Function<\/code>\u00a0\u521b\u5efa\u51fd\u6570\u7684\u5e94\u7528\u573a\u666f\u975e\u5e38\u7279\u6b8a\uff0c\u6bd4\u5982\u5728\u590d\u6742\u7684 Web \u5e94\u7528\u7a0b\u5e8f\u4e2d\uff0c\u6211\u4eec\u9700\u8981\u4ece\u670d\u52a1\u5668\u83b7\u53d6\u4ee3\u7801\u6216\u8005\u52a8\u6001\u5730\u4ece\u6a21\u677f\u7f16\u8bd1\u51fd\u6570\u65f6\u624d\u4f1a\u4f7f\u7528\u3002<\/p>\n<h2>\u95ed\u5305<\/h2>\n<p>\u901a\u5e38\uff0c\u95ed\u5305\u662f\u6307\u4f7f\u7528\u4e00\u4e2a\u7279\u6b8a\u7684\u5c5e\u6027\u00a0<code>[[Environment]]<\/code>\u00a0\u6765\u8bb0\u5f55\u51fd\u6570\u81ea\u8eab\u7684\u521b\u5efa\u65f6\u7684\u73af\u5883\u7684\u51fd\u6570\u3002\u5b83\u5177\u4f53\u6307\u5411\u4e86\u51fd\u6570\u521b\u5efa\u65f6\u7684\u8bcd\u6cd5\u73af\u5883\u3002\uff08\u6211\u4eec\u5728\u00a0<a href=\"https:\/\/zh.javascript.info\/closure\">\u53d8\u91cf\u4f5c\u7528\u57df\uff0c\u95ed\u5305<\/a>\u00a0\u4e00\u7ae0\u4e2d\u5bf9\u6b64\u8fdb\u884c\u4e86\u8be6\u7ec6\u7684\u8bb2\u89e3\uff09\u3002<br \/>\n\u4f46\u662f\u5982\u679c\u6211\u4eec\u4f7f\u7528\u00a0<code>new Function<\/code>\u00a0\u521b\u5efa\u4e00\u4e2a\u51fd\u6570\uff0c\u90a3\u4e48\u8be5\u51fd\u6570\u7684\u00a0<code>[[Environment]]<\/code>\u00a0\u5e76\u4e0d\u6307\u5411\u5f53\u524d\u7684\u8bcd\u6cd5\u73af\u5883\uff0c\u800c\u662f\u6307\u5411\u5168\u5c40\u73af\u5883\u3002<br \/>\n\u56e0\u6b64\uff0c\u6b64\u7c7b\u51fd\u6570\u65e0\u6cd5\u8bbf\u95ee\u5916\u90e8\uff08outer\uff09\u53d8\u91cf\uff0c\u53ea\u80fd\u8bbf\u95ee\u5168\u5c40\u53d8\u91cf\u3002<\/p>\n<pre><code class=\"language-js\">function getFunc() {\n  let value = &quot;test&quot;;\n\n  let func = new Function('alert(value)');\n\n  return func;\n}\n\ngetFunc()(); \/\/ error: value is not defined\n<\/code><\/pre>\n<p><code>new Function<\/code>\u00a0\u7684\u8fd9\u79cd\u7279\u6027\u770b\u8d77\u6765\u6709\u70b9\u5947\u602a\uff0c\u4e0d\u8fc7\u5728\u5b9e\u9645\u4e2d\u5374\u975e\u5e38\u5b9e\u7528\u3002<br \/>\n\u60f3\u8c61\u4e00\u4e0b\u6211\u4eec\u5fc5\u987b\u901a\u8fc7\u4e00\u4e2a\u5b57\u7b26\u4e32\u6765\u521b\u5efa\u4e00\u4e2a\u51fd\u6570\u3002\u5728\u7f16\u5199\u811a\u672c\u65f6\u6211\u4eec\u4e0d\u4f1a\u77e5\u9053\u8be5\u51fd\u6570\u7684\u4ee3\u7801\uff08\u8fd9\u4e5f\u5c31\u662f\u4e3a\u4ec0\u4e48\u6211\u4eec\u4e0d\u7528\u5e38\u89c4\u65b9\u6cd5\u521b\u5efa\u51fd\u6570\uff09\uff0c\u4f46\u5728\u6267\u884c\u8fc7\u7a0b\u4e2d\u4f1a\u77e5\u9053\u4e86\u3002\u6211\u4eec\u53ef\u80fd\u4f1a\u4ece\u670d\u52a1\u5668\u6216\u5176\u4ed6\u6765\u6e90\u83b7\u53d6\u5b83\u3002<br \/>\n\u6211\u4eec\u7684\u65b0\u51fd\u6570\u9700\u8981\u548c\u4e3b\u811a\u672c\u8fdb\u884c\u4ea4\u4e92\u3002<br \/>\n\u5982\u679c\u8fd9\u4e2a\u51fd\u6570\u80fd\u591f\u8bbf\u95ee\u5916\u90e8\uff08outer\uff09\u53d8\u91cf\u4f1a\u600e\u4e48\u6837\uff1f<br \/>\n\u95ee\u9898\u5728\u4e8e\uff0c\u5728\u5c06 JavaScript \u53d1\u5e03\u5230\u751f\u4ea7\u73af\u5883\u4e4b\u524d\uff0c\u9700\u8981\u4f7f\u7528\u00a0<strong>\u538b\u7f29\u7a0b\u5e8f\uff08minifier\uff09<\/strong>\u00a0\u5bf9\u5176\u8fdb\u884c\u538b\u7f29 \u2014\u2014 \u4e00\u4e2a\u7279\u6b8a\u7684\u7a0b\u5e8f\uff0c\u901a\u8fc7\u5220\u9664\u591a\u4f59\u7684\u6ce8\u91ca\u548c\u7a7a\u683c\u7b49\u538b\u7f29\u4ee3\u7801 \u2014\u2014 \u66f4\u91cd\u8981\u7684\u662f\uff0c\u5c06\u5c40\u90e8\u53d8\u91cf\u547d\u540d\u4e3a\u8f83\u77ed\u7684\u53d8\u91cf\u3002<br \/>\n\u4f8b\u5982\uff0c\u5982\u679c\u4e00\u4e2a\u51fd\u6570\u6709\u00a0<code>let userName<\/code>\uff0c\u538b\u7f29\u7a0b\u5e8f\u4f1a\u628a\u5b83\u66ff\u6362\u4e3a\u00a0<code>let a<\/code>\uff08\u5982\u679c a \u5df2\u88ab\u5360\u7528\u4e86\uff0c\u90a3\u5c31\u4f7f\u7528\u5176\u4ed6\u5b57\u7b26\uff09\uff0c\u5269\u4f59\u7684\u5c40\u90e8\u53d8\u91cf\u4e5f\u4f1a\u88ab\u8fdb\u884c\u7c7b\u4f3c\u7684\u66ff\u6362\u3002\u4e00\u822c\u6765\u8bf4\u8fd9\u6837\u7684\u66ff\u6362\u662f\u5b89\u5168\u7684\uff0c\u6bd5\u7adf\u8fd9\u4e9b\u53d8\u91cf\u662f\u51fd\u6570\u5185\u7684\u5c40\u90e8\u53d8\u91cf\uff0c\u51fd\u6570\u5916\u7684\u4efb\u4f55\u4e1c\u897f\u90fd\u65e0\u6cd5\u8bbf\u95ee\u5b83\u3002\u5728\u51fd\u6570\u5185\u90e8\uff0c\u538b\u7f29\u7a0b\u5e8f\u4f1a\u66ff\u6362\u6240\u6709\u4f7f\u7528\u4e86\u8fd9\u4e9b\u53d8\u91cf\u7684\u4ee3\u7801\u3002\u538b\u7f29\u7a0b\u5e8f\u5f88\u806a\u660e\uff0c\u5b83\u4f1a\u5206\u6790\u4ee3\u7801\u7684\u7ed3\u6784\uff0c\u800c\u4e0d\u662f\u5446\u677f\u5730\u67e5\u627e\u7136\u540e\u66ff\u6362\uff0c\u56e0\u6b64\u5b83\u4e0d\u4f1a\u201c\u7834\u574f\u201d\u4f60\u7684\u7a0b\u5e8f\u3002<br \/>\n\u4f46\u662f\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c\u5982\u679c\u4f7f\u00a0<code>new Function<\/code>\u00a0\u53ef\u4ee5\u8bbf\u95ee\u81ea\u8eab\u51fd\u6570\u4ee5\u5916\u7684\u53d8\u91cf\uff0c\u5b83\u4e5f\u5f88\u6709\u53ef\u80fd\u65e0\u6cd5\u627e\u5230\u91cd\u547d\u540d\u7684\u00a0<code>userName<\/code>\uff0c\u8fd9\u662f\u56e0\u4e3a\u65b0\u51fd\u6570\u7684\u521b\u5efa\u53d1\u751f\u5728\u4ee3\u7801\u538b\u7f29\u4ee5\u540e\uff0c\u53d8\u91cf\u540d\u5df2\u7ecf\u88ab\u66ff\u6362\u4e86\u3002<br \/>\n<strong>\u5373\u4f7f\u6211\u4eec\u53ef\u4ee5\u5728\u00a0<code>new Function<\/code>\u00a0\u4e2d\u8bbf\u95ee\u5916\u90e8\u8bcd\u6cd5\u73af\u5883\uff0c\u6211\u4eec\u4e5f\u4f1a\u53d7\u632b\u4e8e\u538b\u7f29\u7a0b\u5e8f\u3002<\/strong><br \/>\n\u6b64\u5916\uff0c\u8fd9\u6837\u7684\u4ee3\u7801\u5728\u67b6\u6784\u4e0a\u5f88\u5dee\u5e76\u4e14\u5bb9\u6613\u51fa\u9519\u3002<br \/>\n\u5f53\u6211\u4eec\u9700\u8981\u5411\u00a0<code>new Function<\/code>\u00a0\u521b\u5efa\u51fa\u7684\u65b0\u51fd\u6570\u4f20\u9012\u6570\u636e\u65f6\uff0c\u6211\u4eec\u5fc5\u987b\u663e\u5f0f\u5730\u901a\u8fc7\u53c2\u6570\u8fdb\u884c\u4f20\u9012\u3002<\/p>\n<h1>\u8c03\u5ea6 setTimeout \u548c setInterval<\/h1>\n<p>\u6709\u65f6\u6211\u4eec\u5e76\u4e0d\u60f3\u7acb\u5373\u6267\u884c\u4e00\u4e2a\u51fd\u6570\uff0c\u800c\u662f\u7b49\u5f85\u7279\u5b9a\u4e00\u6bb5\u65f6\u95f4\u4e4b\u540e\u518d\u6267\u884c\u3002\u8fd9\u5c31\u662f\u6240\u8c13\u7684\u201c\u8ba1\u5212\u8c03\u7528\uff08scheduling a call\uff09\u201d\u3002<br \/>\n\u76ee\u524d\u6709\u4e24\u79cd\u65b9\u5f0f\u53ef\u4ee5\u5b9e\u73b0\uff1a<\/p>\n<ul>\n<li><code>setTimeout<\/code>\u00a0\u5141\u8bb8\u6211\u4eec\u5c06\u51fd\u6570\u63a8\u8fdf\u5230\u4e00\u6bb5\u65f6\u95f4\u95f4\u9694\u4e4b\u540e\u518d\u6267\u884c\u3002<\/li>\n<li><code>setInterval<\/code>\u00a0\u5141\u8bb8\u6211\u4eec\u91cd\u590d\u8fd0\u884c\u4e00\u4e2a\u51fd\u6570\uff0c\u4ece\u4e00\u6bb5\u65f6\u95f4\u95f4\u9694\u4e4b\u540e\u5f00\u59cb\u8fd0\u884c\uff0c\u4e4b\u540e\u4ee5\u8be5\u65f6\u95f4\u95f4\u9694\u8fde\u7eed\u91cd\u590d\u8fd0\u884c\u8be5\u51fd\u6570\u3002<br \/>\n\u8fd9\u4e24\u4e2a\u65b9\u6cd5\u5e76\u4e0d\u5728 JavaScript \u7684\u89c4\u8303\u4e2d\u3002\u4f46\u662f\u5927\u591a\u6570\u8fd0\u884c\u73af\u5883\u90fd\u6709\u5185\u5efa\u7684\u8c03\u5ea6\u7a0b\u5e8f\uff0c\u5e76\u4e14\u63d0\u4f9b\u4e86\u8fd9\u4e9b\u65b9\u6cd5\u3002\u76ee\u524d\u6765\u8bb2\uff0c\u6240\u6709\u6d4f\u89c8\u5668\u4ee5\u53ca Node.js \u90fd\u652f\u6301\u8fd9\u4e24\u4e2a\u65b9\u6cd5\u3002<\/li>\n<\/ul>\n<h2>setTimeout<\/h2>\n<pre><code class=\"language-js\">let timerId = setTimeout(func|code, [delay], [arg1], [arg2], ...)\n<\/code><\/pre>\n<p>\u53c2\u6570\u8bf4\u660e\uff1a<br \/>\n<code>func|code<\/code><br \/>\n\u60f3\u8981\u6267\u884c\u7684\u51fd\u6570\u6216\u4ee3\u7801\u5b57\u7b26\u4e32\u3002 \u4e00\u822c\u4f20\u5165\u7684\u90fd\u662f\u51fd\u6570\u3002\u7531\u4e8e\u67d0\u4e9b\u5386\u53f2\u539f\u56e0\uff0c\u652f\u6301\u4f20\u5165\u4ee3\u7801\u5b57\u7b26\u4e32\uff0c\u4f46\u662f\u4e0d\u5efa\u8bae\u8fd9\u6837\u505a\u3002<br \/>\n<code>delay<\/code><br \/>\n\u6267\u884c\u524d\u7684\u5ef6\u65f6\uff0c\u4ee5\u6beb\u79d2\u4e3a\u5355\u4f4d\uff081000 \u6beb\u79d2 = 1 \u79d2\uff09\uff0c\u9ed8\u8ba4\u503c\u662f 0\uff1b<br \/>\n<code>arg1<\/code>\uff0c<code>arg2<\/code>\u2026<br \/>\n\u8981\u4f20\u5165\u88ab\u6267\u884c\u51fd\u6570\uff08\u6216\u4ee3\u7801\u5b57\u7b26\u4e32\uff09\u7684\u53c2\u6570\u5217\u8868\uff08IE9 \u4ee5\u4e0b\u4e0d\u652f\u6301\uff09<br \/>\n\u5982\u679c\u7b2c\u4e00\u4e2a\u53c2\u6570\u4f4d\u4f20\u5165\u7684\u662f\u5b57\u7b26\u4e32\uff0cJavaScript \u4f1a\u81ea\u52a8\u4e3a\u5176\u521b\u5efa\u4e00\u4e2a\u51fd\u6570\u3002<br \/>\n\u4f46\u662f\uff0c\u4e0d\u5efa\u8bae\u4f7f\u7528\u5b57\u7b26\u4e32\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u7bad\u5934\u51fd\u6570\u4ee3\u66ff\u5b83\u4eec<\/p>\n<blockquote>\n<p>\u4f20\u5165\u4e00\u4e2a\u51fd\u6570\uff0c\u4f46\u4e0d\u8981\u6267\u884c\u5b83<br \/>\n\u65b0\u624b\u5f00\u53d1\u8005\u6709\u65f6\u5019\u4f1a\u8bef\u5c06\u4e00\u5bf9\u62ec\u53f7\u00a0<code>()<\/code>\u00a0\u52a0\u5728\u51fd\u6570\u540e\u9762<br \/>\n\u8fd9\u6837\u4e0d\u884c\uff0c\u56e0\u4e3a\u00a0<code>setTimeout<\/code>\u00a0\u671f\u671b\u5f97\u5230\u4e00\u4e2a\u5bf9\u51fd\u6570\u7684\u5f15\u7528\u3002\u800c\u8fd9\u91cc\u7684\u00a0<code>sayHi()<\/code>\u00a0\u5f88\u660e\u663e\u662f\u5728\u6267\u884c\u51fd\u6570\uff0c\u6240\u4ee5\u5b9e\u9645\u4e0a\u4f20\u5165\u00a0<code>setTimeout<\/code>\u00a0\u7684\u662f\u00a0<strong>\u51fd\u6570\u7684\u6267\u884c\u7ed3\u679c<\/strong>\u3002\u5728\u8fd9\u4e2a\u4f8b\u5b50\u4e2d\uff0c<code>sayHi()<\/code>\u00a0\u7684\u6267\u884c\u7ed3\u679c\u662f\u00a0<code>undefined<\/code>\uff08\u4e5f\u5c31\u662f\u8bf4\u51fd\u6570\u6ca1\u6709\u8fd4\u56de\u4efb\u4f55\u7ed3\u679c\uff09\uff0c\u6240\u4ee5\u5b9e\u9645\u4e0a\u4ec0\u4e48\u4e5f\u6ca1\u6709\u8c03\u5ea6\u3002<\/p>\n<\/blockquote>\n<h3>\u7528 clearTimeout \u6765\u53d6\u6d88\u8c03\u5ea6<\/h3>\n<p><code>setTimeout<\/code>\u00a0\u5728\u8c03\u7528\u65f6\u4f1a\u8fd4\u56de\u4e00\u4e2a\u201c\u5b9a\u65f6\u5668\u6807\u8bc6\u7b26\uff08timer identifier\uff09\u201d\uff0c\u5728\u6211\u4eec\u7684\u4f8b\u5b50\u4e2d\u662f\u00a0<code>timerId<\/code>\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u5b83\u6765\u53d6\u6d88\u6267\u884c\u3002<br \/>\n\u53d6\u6d88\u8c03\u5ea6\u7684\u8bed\u6cd5\uff1a<\/p>\n<pre><code class=\"language-js\">let timerId = setTimeout(...);\nclearTimeout(timerId);\n<\/code><\/pre>\n<p>\u4ece\u00a0<code>alert<\/code>\u00a0\u7684\u8f93\u51fa\u6765\u770b\uff0c\u5728\u6d4f\u89c8\u5668\u4e2d\uff0c\u5b9a\u65f6\u5668\u6807\u8bc6\u7b26\u662f\u4e00\u4e2a\u6570\u5b57\u3002\u5728\u5176\u4ed6\u73af\u5883\u4e2d\uff0c\u53ef\u80fd\u662f\u5176\u4ed6\u7684\u4e1c\u897f\u3002\u4f8b\u5982 Node.js \u8fd4\u56de\u7684\u662f\u4e00\u4e2a\u5b9a\u65f6\u5668\u5bf9\u8c61\uff0c\u8fd9\u4e2a\u5bf9\u8c61\u5305\u542b\u4e00\u7cfb\u5217\u65b9\u6cd5\u3002<br \/>\n\u6211\u518d\u91cd\u7533\u4e00\u904d\uff0c\u8fd9\u4e9b\u65b9\u6cd5\u6ca1\u6709\u7edf\u4e00\u7684\u89c4\u8303\u5b9a\u4e49\uff0c\u6240\u4ee5\u8fd9\u6ca1\u4ec0\u4e48\u95ee\u9898\u3002<br \/>\n\u9488\u5bf9\u6d4f\u89c8\u5668\u73af\u5883\uff0c\u5b9a\u65f6\u5668\u5728 HTML5 \u7684\u6807\u51c6\u4e2d\u6709\u8be6\u7ec6\u63cf\u8ff0\uff0c\u8be6\u89c1\u00a0<a href=\"https:\/\/www.w3.org\/TR\/html5\/webappapis.html#timers\">timers section<\/a>\u3002<\/p>\n<h2>setInterval<\/h2>\n<p><code>setInterval<\/code>\u00a0\u65b9\u6cd5\u548c\u00a0<code>setTimeout<\/code>\u00a0\u7684\u8bed\u6cd5\u76f8\u540c\uff1a<\/p>\n<pre><code class=\"language-js\">let timerId = setInterval(func|code, [delay], [arg1], [arg2], ...)\n<\/code><\/pre>\n<p>\u6240\u6709\u53c2\u6570\u7684\u610f\u4e49\u4e5f\u662f\u76f8\u540c\u7684\u3002\u4e0d\u8fc7\u4e0e\u00a0<code>setTimeout<\/code>\u00a0\u53ea\u6267\u884c\u4e00\u6b21\u4e0d\u540c\uff0c<code>setInterval<\/code>\u00a0\u662f\u6bcf\u95f4\u9694\u7ed9\u5b9a\u7684\u65f6\u95f4\u5468\u671f\u6027\u6267\u884c\u3002<br \/>\n\u60f3\u8981\u963b\u6b62\u540e\u7eed\u8c03\u7528\uff0c\u6211\u4eec\u9700\u8981\u8c03\u7528\u00a0<code>clearInterval(timerId)<\/code>\u3002<\/p>\n<blockquote>\n<p>alert \u5f39\u7a97\u663e\u793a\u7684\u65f6\u5019\u8ba1\u65f6\u5668\u4f9d\u7136\u5728\u8fdb\u884c\u8ba1\u65f6<br \/>\n\u5728\u5927\u591a\u6570\u6d4f\u89c8\u5668\u4e2d\uff0c\u5305\u62ec Chrome \u548c Firefox\uff0c\u5728\u663e\u793a\u00a0<code>alert\/confirm\/prompt<\/code>\u00a0\u5f39\u7a97\u65f6\uff0c\u5185\u90e8\u7684\u5b9a\u65f6\u5668\u4ecd\u65e7\u4f1a\u7ee7\u7eed\u201c\u5600\u55d2\u201d\u3002<br \/>\n\u6240\u4ee5\uff0c\u5728\u8fd0\u884c\u4e0a\u9762\u7684\u4ee3\u7801\u65f6\uff0c\u5982\u679c\u5728\u4e00\u5b9a\u65f6\u95f4\u5185\u6ca1\u6709\u5173\u6389\u00a0<code>alert<\/code>\u00a0\u5f39\u7a97\uff0c\u90a3\u4e48\u5728\u4f60\u5173\u95ed\u5f39\u7a97\u540e\uff0c\u4e0b\u4e00\u4e2a\u00a0<code>alert<\/code>\u00a0\u4f1a\u7acb\u5373\u663e\u793a\u3002\u4e24\u6b21\u00a0<code>alert<\/code>\u00a0\u4e4b\u95f4\u7684\u65f6\u95f4\u95f4\u9694\u5c06\u5c0f\u4e8e 2 \u79d2\u3002<\/p>\n<\/blockquote>\n<h2>\u5d4c\u5957\u7684 setTimeout<\/h2>\n<p>\u5468\u671f\u6027\u8c03\u5ea6\u6709\u4e24\u79cd\u65b9\u5f0f\u3002<br \/>\n\u4e00\u79cd\u662f\u4f7f\u7528\u00a0<code>setInterval<\/code>\uff0c\u53e6\u5916\u4e00\u79cd\u5c31\u662f\u5d4c\u5957\u7684\u00a0<code>setTimeout<\/code>\uff0c\u5c31\u50cf\u8fd9\u6837<\/p>\n<pre><code class=\"language-js\">\/** instead of:\nlet timerId = setInterval(() =&gt; alert('tick'), 2000);\n*\/\n\nlet timerId = setTimeout(function tick() {\n  alert('tick');\n  timerId = setTimeout(tick, 2000); \/\/ (*)\n}, 2000);\n<\/code><\/pre>\n<p>\u4e0a\u9762\u8fd9\u4e2a\u00a0<code>setTimeout<\/code>\u00a0\u5728\u5f53\u524d\u8fd9\u4e00\u6b21\u51fd\u6570\u6267\u884c\u5b8c\u65f6\u00a0<code>(*)<\/code>\u00a0\u7acb\u5373\u8c03\u5ea6\u4e0b\u4e00\u6b21\u8c03\u7528\u3002<br \/>\n\u5d4c\u5957\u7684\u00a0<code>setTimeout<\/code>\u00a0\u8981\u6bd4\u00a0<code>setInterval<\/code>\u00a0\u7075\u6d3b\u5f97\u591a\u3002\u91c7\u7528\u8fd9\u79cd\u65b9\u5f0f\u53ef\u4ee5\u6839\u636e\u5f53\u524d\u6267\u884c\u7ed3\u679c\u6765\u8c03\u5ea6\u4e0b\u4e00\u6b21\u8c03\u7528\uff0c\u56e0\u6b64\u4e0b\u4e00\u6b21\u8c03\u7528\u53ef\u4ee5\u4e0e\u5f53\u524d\u8fd9\u4e00\u6b21\u4e0d\u540c\u3002<br \/>\n\u4f8b\u5982\uff0c\u6211\u4eec\u8981\u5b9e\u73b0\u4e00\u4e2a\u670d\u52a1\uff08server\uff09\uff0c\u6bcf\u95f4\u9694 5 \u79d2\u5411\u670d\u52a1\u5668\u53d1\u9001\u4e00\u4e2a\u6570\u636e\u8bf7\u6c42\uff0c\u4f46\u5982\u679c\u670d\u52a1\u5668\u8fc7\u8f7d\u4e86\uff0c\u90a3\u4e48\u5c31\u8981\u964d\u4f4e\u8bf7\u6c42\u9891\u7387\uff0c\u6bd4\u5982\u5c06\u95f4\u9694\u589e\u52a0\u5230 10\u300120\u300140 \u79d2\u7b49\u3002<br \/>\n\u5e76\u4e14\uff0c\u5982\u679c\u6211\u4eec\u8c03\u5ea6\u7684\u51fd\u6570\u5360\u7528\u5927\u91cf\u7684 CPU\uff0c\u90a3\u4e48\u6211\u4eec\u53ef\u4ee5\u6d4b\u91cf\u6267\u884c\u6240\u9700\u8981\u82b1\u8d39\u7684\u65f6\u95f4\uff0c\u5e76\u5b89\u6392\u4e0b\u6b21\u8c03\u7528\u662f\u5e94\u8be5\u63d0\u524d\u8fd8\u662f\u63a8\u8fdf\u3002<br \/>\n<strong>\u5d4c\u5957\u7684\u00a0<code>setTimeout<\/code>\u00a0\u76f8\u8f83\u4e8e\u00a0<code>setInterval<\/code>\u00a0\u80fd\u591f\u66f4\u7cbe\u786e\u5730\u8bbe\u7f6e\u4e24\u6b21\u6267\u884c\u4e4b\u95f4\u7684\u5ef6\u65f6\u3002<\/strong><br \/>\n<strong>\u4f7f\u7528\u00a0<code>setInterval<\/code>\u00a0\u65f6\uff0c<code>func<\/code>\u00a0\u51fd\u6570\u7684\u5b9e\u9645\u8c03\u7528\u95f4\u9694\u8981\u6bd4\u4ee3\u7801\u4e2d\u8bbe\u5b9a\u7684\u65f6\u95f4\u95f4\u9694\u8981\u77ed\uff01<\/strong><br \/>\n\u8fd9\u4e5f\u662f\u6b63\u5e38\u7684\uff0c\u56e0\u4e3a\u00a0<code>func<\/code>\u00a0\u7684\u6267\u884c\u6240\u82b1\u8d39\u7684\u65f6\u95f4\u201c\u6d88\u8017\u201d\u4e86\u4e00\u90e8\u5206\u95f4\u9694\u65f6\u95f4\u3002<br \/>\n\u4e5f\u53ef\u80fd\u51fa\u73b0\u8fd9\u79cd\u60c5\u51b5\uff0c\u5c31\u662f\u00a0<code>func<\/code>\u00a0\u7684\u6267\u884c\u6240\u82b1\u8d39\u7684\u65f6\u95f4\u6bd4\u6211\u4eec\u9884\u671f\u7684\u65f6\u95f4\u66f4\u957f\uff0c\u5e76\u4e14\u8d85\u51fa\u4e86 100 \u6beb\u79d2\u3002<br \/>\n\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0cJavaScript \u5f15\u64ce\u4f1a\u7b49\u5f85\u00a0<code>func<\/code>\u00a0\u6267\u884c\u5b8c\u6210\uff0c\u7136\u540e\u68c0\u67e5\u8c03\u5ea6\u7a0b\u5e8f\uff0c\u5982\u679c\u65f6\u95f4\u5230\u4e86\uff0c\u5219\u00a0<strong>\u7acb\u5373<\/strong>\u00a0\u518d\u6b21\u6267\u884c\u5b83\u3002<br \/>\n\u6781\u7aef\u60c5\u51b5\u4e0b\uff0c\u5982\u679c\u51fd\u6570\u6bcf\u6b21\u6267\u884c\u65f6\u95f4\u90fd\u8d85\u8fc7\u00a0<code>delay<\/code>\u00a0\u8bbe\u7f6e\u7684\u65f6\u95f4\uff0c\u90a3\u4e48\u6bcf\u6b21\u8c03\u7528\u4e4b\u95f4\u5c06\u5b8c\u5168\u6ca1\u6709\u505c\u987f\u3002<br \/>\n<strong>\u5d4c\u5957\u7684\u00a0<code>setTimeout<\/code>\u00a0\u5c31\u80fd\u786e\u4fdd\u5ef6\u65f6\u7684\u56fa\u5b9a\uff08\u8fd9\u91cc\u662f 100 \u6beb\u79d2\uff09\u3002<\/strong><br \/>\n\u8fd9\u662f\u56e0\u4e3a\u4e0b\u4e00\u6b21\u8c03\u7528\u662f\u5728\u524d\u4e00\u6b21\u8c03\u7528\u5b8c\u6210\u65f6\u518d\u8c03\u5ea6\u7684\u3002<\/p>\n<blockquote>\n<p>\u5783\u573e\u56de\u6536\u548c setInterval\/setTimeout \u56de\u8c03\uff08callback\uff09<br \/>\n\u5f53\u4e00\u4e2a\u51fd\u6570\u4f20\u5165\u00a0<code>setInterval\/setTimeout<\/code>\u00a0\u65f6\uff0c\u5c06\u4e3a\u5176\u521b\u5efa\u4e00\u4e2a\u5185\u90e8\u5f15\u7528\uff0c\u5e76\u4fdd\u5b58\u5728\u8c03\u5ea6\u7a0b\u5e8f\u4e2d\u3002\u8fd9\u6837\uff0c\u5373\u4f7f\u8fd9\u4e2a\u51fd\u6570\u6ca1\u6709\u5176\u4ed6\u5f15\u7528\uff0c\u4e5f\u80fd\u9632\u6b62\u5783\u573e\u56de\u6536\u5668\uff08GC\uff09\u5c06\u5176\u56de\u6536\u3002<br \/>\n\u5bf9\u4e8e\u00a0<code>setInterval<\/code>\uff0c\u4f20\u5165\u7684\u51fd\u6570\u4e5f\u662f\u4e00\u76f4\u5b58\u5728\u4e8e\u5185\u5b58\u4e2d\uff0c\u76f4\u5230\u00a0<code>clearInterval<\/code>\u00a0\u88ab\u8c03\u7528\u3002<br \/>\n\u8fd9\u91cc\u8fd8\u8981\u63d0\u5230\u4e00\u4e2a\u526f\u4f5c\u7528\u3002\u5982\u679c\u51fd\u6570\u5f15\u7528\u4e86\u5916\u90e8\u53d8\u91cf\uff08\u8bd1\u6ce8\uff1a\u95ed\u5305\uff09\uff0c\u90a3\u4e48\u53ea\u8981\u8fd9\u4e2a\u51fd\u6570\u8fd8\u5b58\u5728\uff0c\u5916\u90e8\u53d8\u91cf\u4e5f\u4f1a\u968f\u4e4b\u5b58\u5728\u3002\u5b83\u4eec\u53ef\u80fd\u6bd4\u51fd\u6570\u672c\u8eab\u5360\u7528\u66f4\u591a\u7684\u5185\u5b58\u3002\u56e0\u6b64\uff0c\u5f53\u6211\u4eec\u4e0d\u518d\u9700\u8981\u8c03\u5ea6\u51fd\u6570\u65f6\uff0c\u6700\u597d\u53d6\u6d88\u5b83\uff0c\u5373\u4f7f\u8fd9\u662f\u4e2a\uff08\u5360\u7528\u5185\u5b58\uff09\u5f88\u5c0f\u7684\u51fd\u6570\u3002<\/p>\n<\/blockquote>\n<h2>\u96f6\u5ef6\u65f6\u7684 setTimeout<\/h2>\n<p>\u8fd9\u513f\u6709\u4e00\u79cd\u7279\u6b8a\u7684\u7528\u6cd5\uff1a<code>setTimeout(func, 0)<\/code>\uff0c\u6216\u8005\u4ec5\u4ec5\u662f\u00a0<code>setTimeout(func)<\/code>\u3002<br \/>\n\u8fd9\u6837\u8c03\u5ea6\u53ef\u4ee5\u8ba9\u00a0<code>func<\/code>\u00a0\u5c3d\u5feb\u6267\u884c\u3002\u4f46\u662f\u53ea\u6709\u5728\u5f53\u524d\u6b63\u5728\u6267\u884c\u7684\u811a\u672c\u6267\u884c\u5b8c\u6210\u540e\uff0c\u8c03\u5ea6\u7a0b\u5e8f\u624d\u4f1a\u8c03\u7528\u5b83\u3002<br \/>\n\u4e5f\u5c31\u662f\u8bf4\uff0c\u8be5\u51fd\u6570\u88ab\u8c03\u5ea6\u5728\u5f53\u524d\u811a\u672c\u6267\u884c\u5b8c\u6210\u201c\u4e4b\u540e\u201d\u7acb\u5373\u6267\u884c\u3002<\/p>\n<pre><code class=\"language-js\">setTimeout(() =&gt; alert(&quot;World&quot;));\n\nalert(&quot;Hello&quot;);\n<\/code><\/pre>\n<p>\u7b2c\u4e00\u884c\u4ee3\u7801\u201c\u5c06\u8c03\u7528\u5b89\u6392\u5230\u65e5\u7a0b\uff08calendar\uff090 \u6beb\u79d2\u5904\u201d\u3002\u4f46\u662f\u8c03\u5ea6\u7a0b\u5e8f\u53ea\u6709\u5728\u5f53\u524d\u811a\u672c\u6267\u884c\u5b8c\u6bd5\u65f6\u624d\u4f1a\u53bb\u201c\u68c0\u67e5\u65e5\u7a0b\u201d\uff0c\u6240\u4ee5\u5148\u8f93\u51fa\u00a0<code>&quot;Hello&quot;<\/code>\uff0c\u7136\u540e\u624d\u8f93\u51fa\u00a0<code>&quot;World&quot;<\/code>\u3002<br \/>\n\u6b64\u5916\uff0c\u8fd8\u6709\u4e0e\u6d4f\u89c8\u5668\u76f8\u5173\u7684 0 \u5ef6\u65f6 timeout \u7684\u9ad8\u7ea7\u7528\u4f8b\uff0c\u6211\u4eec\u5c06\u5728\u00a0<a href=\"https:\/\/zh.javascript.info\/event-loop\">\u4e8b\u4ef6\u5faa\u73af\uff1a\u5fae\u4efb\u52a1\u548c\u5b8f\u4efb\u52a1<\/a>\u00a0\u4e00\u7ae0\u4e2d\u8be6\u7ec6\u8bb2\u89e3\u3002<\/p>\n<blockquote>\n<p>\u96f6\u5ef6\u65f6\u5b9e\u9645\u4e0a\u4e0d\u4e3a\u96f6\uff08\u5728\u6d4f\u89c8\u5668\u4e2d\uff09<br \/>\n\u5728\u6d4f\u89c8\u5668\u73af\u5883\u4e0b\uff0c\u5d4c\u5957\u5b9a\u65f6\u5668\u7684\u8fd0\u884c\u9891\u7387\u662f\u53d7\u9650\u5236\u7684\u3002\u6839\u636e\u00a0<a href=\"https:\/\/html.spec.whatwg.org\/multipage\/timers-and-user-prompts.html#timers\">HTML5 \u6807\u51c6<\/a>\u00a0\u6240\u8bb2\uff1a\u201c\u7ecf\u8fc7 5 \u91cd\u5d4c\u5957\u5b9a\u65f6\u5668\u4e4b\u540e\uff0c\u65f6\u95f4\u95f4\u9694\u88ab\u5f3a\u5236\u8bbe\u5b9a\u4e3a\u81f3\u5c11 4 \u6beb\u79d2\u201d\u3002<br \/>\n\u8ba9\u6211\u4eec\u7528\u4e0b\u9762\u7684\u793a\u4f8b\u6765\u770b\u770b\u8fd9\u5230\u5e95\u662f\u4ec0\u4e48\u610f\u601d\u3002\u5176\u4e2d\u00a0<code>setTimeout<\/code>\u00a0\u8c03\u7528\u4f1a\u4ee5\u96f6\u5ef6\u65f6\u91cd\u65b0\u8c03\u5ea6\u81ea\u8eab\u7684\u8c03\u7528\u3002\u6bcf\u6b21\u8c03\u7528\u90fd\u4f1a\u5728\u00a0<code>times<\/code>\u00a0\u6570\u7ec4\u4e2d\u8bb0\u5f55\u4e0a\u4e00\u6b21\u8c03\u7528\u7684\u5b9e\u9645\u65f6\u95f4\u3002\u90a3\u4e48\u771f\u6b63\u7684\u5ef6\u8fdf\u662f\u4ec0\u4e48\u6837\u7684\uff1f\u8ba9\u6211\u4eec\u6765\u770b\u770b\uff1a<\/p>\n<\/blockquote>\n<pre><code class=\"language-js\">let start = Date.now();\nlet times = [];\n\nsetTimeout(function run() {\n  times.push(Date.now() - start); \/\/ \u4fdd\u5b58\u524d\u4e00\u4e2a\u8c03\u7528\u7684\u5ef6\u65f6\n\n  if (start + 100 &lt; Date.now()) alert(times); \/\/ 100 \u6beb\u79d2\u4e4b\u540e\uff0c\u663e\u793a\u5ef6\u65f6\u4fe1\u606f\n  else setTimeout(run); \/\/ \u5426\u5219\u91cd\u65b0\u8c03\u5ea6\n});\n\n\/\/ \u8f93\u51fa\u793a\u4f8b\uff1a\n\/\/ 1,1,1,1,9,15,20,24,30,35,40,45,50,55,59,64,70,75,80,85,90,95,100\n<\/code><\/pre>\n<blockquote>\n<p>\u7b2c\u4e00\u6b21\uff0c\u5b9a\u65f6\u5668\u662f\u7acb\u5373\u6267\u884c\u7684\uff08\u6b63\u5982\u89c4\u8303\u91cc\u6240\u63cf\u8ff0\u7684\u90a3\u6837\uff09\uff0c\u63a5\u4e0b\u6765\u6211\u4eec\u53ef\u4ee5\u770b\u5230\u00a0<code>9, 15, 20, 24...<\/code>\u3002\u4e24\u6b21\u8c03\u7528\u4e4b\u95f4\u5fc5\u987b\u7ecf\u8fc7 4 \u6beb\u79d2\u4ee5\u4e0a\u7684\u5f3a\u5236\u5ef6\u65f6\u3002\uff08\u8bd1\u6ce8\uff1a\u8fd9\u91cc\u4f5c\u8005\u6ca1\u8bf4\u6e05\u695a\uff0ctimer \u6570\u7ec4\u91cc\u5b58\u653e\u7684\u662f\u6bcf\u6b21\u5b9a\u65f6\u5668\u8fd0\u884c\u7684\u65f6\u523b\u4e0e start \u7684\u5dee\u503c\uff0c\u6240\u4ee5\u6570\u5b57\u53ea\u4f1a\u8d8a\u6765\u8d8a\u5927\uff0c\u5b9e\u9645\u4e0a\u524d\u540e\u8c03\u7528\u7684\u5ef6\u65f6\u662f\u6570\u7ec4\u503c\u7684\u5dee\u503c\u3002\u793a\u4f8b\u4e2d\u524d\u51e0\u6b21\u90fd\u662f 1\uff0c\u6240\u4ee5\u5ef6\u65f6\u4e3a 0\uff09<br \/>\n\u5982\u679c\u6211\u4eec\u4f7f\u7528\u00a0<code>setInterval<\/code>\u00a0\u800c\u4e0d\u662f\u00a0<code>setTimeout<\/code>\uff0c\u4e5f\u4f1a\u53d1\u751f\u7c7b\u4f3c\u7684\u60c5\u51b5\uff1a<code>setInterval(f)<\/code>\u00a0\u4f1a\u4ee5\u96f6\u5ef6\u65f6\u8fd0\u884c\u51e0\u6b21\u00a0<code>f<\/code>\uff0c\u7136\u540e\u4ee5 4 \u6beb\u79d2\u4ee5\u4e0a\u7684\u5f3a\u5236\u5ef6\u65f6\u8fd0\u884c\u3002<br \/>\n\u8fd9\u4e2a\u9650\u5236\u6765\u81ea\u201c\u8fdc\u53e4\u65f6\u4ee3\u201d\uff0c\u5e76\u4e14\u8bb8\u591a\u811a\u672c\u90fd\u4f9d\u8d56\u4e8e\u6b64\uff0c\u6240\u4ee5\u8fd9\u4e2a\u673a\u5236\u4e5f\u5c31\u5b58\u5728\u81f3\u4eca\u3002<br \/>\n\u5bf9\u4e8e\u670d\u52a1\u7aef\u7684 JavaScript\uff0c\u5c31\u6ca1\u6709\u8fd9\u4e2a\u9650\u5236\uff0c\u5e76\u4e14\u8fd8\u6709\u5176\u4ed6\u8c03\u5ea6\u5373\u65f6\u5f02\u6b65\u4efb\u52a1\u7684\u65b9\u5f0f\u3002\u4f8b\u5982 Node.js \u7684\u00a0<a href=\"https:\/\/nodejs.org\/api\/timers.html#timers_setimmediate_callback_args\">setImmediate<\/a>\u3002\u56e0\u6b64\uff0c\u8fd9\u4e2a\u63d0\u9192\u53ea\u662f\u9488\u5bf9\u6d4f\u89c8\u5668\u73af\u5883\u7684\u3002<\/p>\n<\/blockquote>\n<h1>\u88c5\u9970\u5668\u6a21\u5f0f\u548c\u8f6c\u53d1 call\/apply<\/h1>\n<p>JavaScript \u5728\u5904\u7406\u51fd\u6570\u65f6\u63d0\u4f9b\u4e86\u975e\u51e1\u7684\u7075\u6d3b\u6027\u3002\u5b83\u4eec\u53ef\u4ee5\u88ab\u4f20\u9012\uff0c\u7528\u4f5c\u5bf9\u8c61\uff0c\u73b0\u5728\u6211\u4eec\u5c06\u770b\u5230\u5982\u4f55\u5728\u5b83\u4eec\u4e4b\u95f4\u00a0<strong>\u8f6c\u53d1\uff08forward\uff09<\/strong>\u00a0\u8c03\u7528\u5e76\u00a0<strong>\u88c5\u9970\uff08decorate\uff09<\/strong>\u00a0\u5b83\u4eec\u3002<\/p>\n<h2>\u900f\u660e\u7f13\u5b58<\/h2>\n<p>\u5047\u8bbe\u6211\u4eec\u6709\u4e00\u4e2a CPU \u91cd\u8d1f\u8f7d\u7684\u51fd\u6570\u00a0<code>slow(x)<\/code>\uff0c\u4f46\u5b83\u7684\u7ed3\u679c\u662f\u7a33\u5b9a\u7684\u3002\u6362\u53e5\u8bdd\u8bf4\uff0c\u5bf9\u4e8e\u76f8\u540c\u7684\u00a0<code>x<\/code>\uff0c\u5b83\u603b\u662f\u8fd4\u56de\u76f8\u540c\u7684\u7ed3\u679c\u3002<br \/>\n\u5982\u679c\u7ecf\u5e38\u8c03\u7528\u8be5\u51fd\u6570\uff0c\u6211\u4eec\u53ef\u80fd\u5e0c\u671b\u5c06\u7ed3\u679c\u7f13\u5b58\uff08\u8bb0\u4f4f\uff09\u4e0b\u6765\uff0c\u4ee5\u907f\u514d\u5728\u91cd\u65b0\u8ba1\u7b97\u4e0a\u82b1\u8d39\u989d\u5916\u7684\u65f6\u95f4\u3002<br \/>\n\u4f46\u662f\u6211\u4eec\u4e0d\u662f\u5c06\u8fd9\u4e2a\u529f\u80fd\u6dfb\u52a0\u5230\u00a0<code>slow()<\/code>\u00a0\u4e2d\uff0c\u800c\u662f\u521b\u5efa\u4e00\u4e2a\u5305\u88c5\u5668\uff08wrapper\uff09\u51fd\u6570\uff0c\u8be5\u51fd\u6570\u589e\u52a0\u4e86\u7f13\u5b58\u529f\u80fd\u3002\u6b63\u5982\u6211\u4eec\u5c06\u8981\u770b\u5230\u7684\uff0c\u8fd9\u6837\u505a\u6709\u5f88\u591a\u597d\u5904\u3002<br \/>\n\u4e0b\u9762\u662f\u4ee3\u7801\u548c\u89e3\u91ca<\/p>\n<pre><code class=\"language-js\">function slow(x) {\n  \/\/ \u8fd9\u91cc\u53ef\u80fd\u4f1a\u6709\u91cd\u8d1f\u8f7d\u7684 CPU \u5bc6\u96c6\u578b\u5de5\u4f5c\n  alert(`Called with ${x}`);\n  return x;\n}\n\nfunction cachingDecorator(func) {\n  let cache = new Map();\n\n  return function(x) {\n    if (cache.has(x)) {    \/\/ \u5982\u679c\u7f13\u5b58\u4e2d\u6709\u5bf9\u5e94\u7684\u7ed3\u679c\n      return cache.get(x); \/\/ \u4ece\u7f13\u5b58\u4e2d\u8bfb\u53d6\u7ed3\u679c\n    }\n\n    let result = func(x);  \/\/ \u5426\u5219\u5c31\u8c03\u7528 func\n\n    cache.set(x, result);  \/\/ \u7136\u540e\u5c06\u7ed3\u679c\u7f13\u5b58\uff08\u8bb0\u4f4f\uff09\u4e0b\u6765\n    return result;\n  };\n}\n\nslow = cachingDecorator(slow);\n\nalert( slow(1) ); \/\/ slow(1) \u88ab\u7f13\u5b58\u4e0b\u6765\u4e86\uff0c\u5e76\u8fd4\u56de\u7ed3\u679c\nalert( &quot;Again: &quot; + slow(1) ); \/\/ \u8fd4\u56de\u7f13\u5b58\u4e2d\u7684 slow(1) \u7684\u7ed3\u679c\n\nalert( slow(2) ); \/\/ slow(2) \u88ab\u7f13\u5b58\u4e0b\u6765\u4e86\uff0c\u5e76\u8fd4\u56de\u7ed3\u679c\nalert( &quot;Again: &quot; + slow(2) ); \/\/ \u8fd4\u56de\u7f13\u5b58\u4e2d\u7684 slow(2) \u7684\u7ed3\u679c\n<\/code><\/pre>\n<p>\u5728\u4e0a\u9762\u7684\u4ee3\u7801\u4e2d\uff0c<code>cachingDecorator<\/code>\u00a0\u662f\u4e00\u4e2a\u00a0<strong>\u88c5\u9970\u5668\uff08decorator\uff09<\/strong>\uff1a\u4e00\u4e2a\u7279\u6b8a\u7684\u51fd\u6570\uff0c\u5b83\u63a5\u53d7\u53e6\u4e00\u4e2a\u51fd\u6570\u5e76\u6539\u53d8\u5b83\u7684\u884c\u4e3a\u3002<br \/>\n\u5176\u601d\u60f3\u662f\uff0c\u6211\u4eec\u53ef\u4ee5\u4e3a\u4efb\u4f55\u51fd\u6570\u8c03\u7528\u00a0<code>cachingDecorator<\/code>\uff0c\u5b83\u5c06\u8fd4\u56de\u7f13\u5b58\u5305\u88c5\u5668\u3002\u8fd9\u5f88\u68d2\u554a\uff0c\u56e0\u4e3a\u6211\u4eec\u6709\u5f88\u591a\u51fd\u6570\u53ef\u4ee5\u4f7f\u7528\u8fd9\u6837\u7684\u7279\u6027\uff0c\u800c\u6211\u4eec\u9700\u8981\u505a\u7684\u5c31\u662f\u5c06\u00a0<code>cachingDecorator<\/code>\u00a0\u5e94\u7528\u4e8e\u5b83\u4eec\u3002<br \/>\n\u901a\u8fc7\u5c06\u7f13\u5b58\u4e0e\u4e3b\u51fd\u6570\u4ee3\u7801\u5206\u5f00\uff0c\u6211\u4eec\u8fd8\u53ef\u4ee5\u4f7f\u4e3b\u51fd\u6570\u4ee3\u7801\u53d8\u5f97\u66f4\u7b80\u5355\u3002<br \/>\n<code>cachingDecorator(func)<\/code>\u00a0\u7684\u7ed3\u679c\u662f\u4e00\u4e2a\u201c\u5305\u88c5\u5668\u201d\uff1a<code>function(x)<\/code>\u00a0\u5c06\u00a0<code>func(x)<\/code>\u00a0\u7684\u8c03\u7528\u201c\u5305\u88c5\u201d\u5230\u7f13\u5b58\u903b\u8f91\u4e2d<br \/>\n\u4ece\u5916\u90e8\u4ee3\u7801\u6765\u770b\uff0c\u5305\u88c5\u7684\u00a0<code>slow<\/code>\u00a0\u51fd\u6570\u6267\u884c\u7684\u4ecd\u7136\u662f\u4e0e\u4e4b\u524d\u76f8\u540c\u7684\u64cd\u4f5c\u3002\u5b83\u53ea\u662f\u5728\u5176\u884c\u4e3a\u4e0a\u6dfb\u52a0\u4e86\u7f13\u5b58\u529f\u80fd\u3002<br \/>\n\u603b\u800c\u8a00\u4e4b\uff0c\u4f7f\u7528\u5206\u79bb\u7684\u00a0<code>cachingDecorator<\/code>\u00a0\u800c\u4e0d\u662f\u6539\u53d8\u00a0<code>slow<\/code>\u00a0\u672c\u8eab\u7684\u4ee3\u7801\u6709\u51e0\u4e2a\u597d\u5904\uff1a<\/p>\n<ul>\n<li><code>cachingDecorator<\/code>\u00a0\u662f\u53ef\u91cd\u7528\u7684\u3002\u6211\u4eec\u53ef\u4ee5\u5c06\u5b83\u5e94\u7528\u4e8e\u53e6\u4e00\u4e2a\u51fd\u6570\u3002<\/li>\n<li>\u7f13\u5b58\u903b\u8f91\u662f\u72ec\u7acb\u7684\uff0c\u5b83\u6ca1\u6709\u589e\u52a0\u00a0<code>slow<\/code>\u00a0\u672c\u8eab\u7684\u590d\u6742\u6027\uff08\u5982\u679c\u6709\u7684\u8bdd\uff09\u3002<\/li>\n<li>\u5982\u679c\u9700\u8981\uff0c\u6211\u4eec\u53ef\u4ee5\u7ec4\u5408\u591a\u4e2a\u88c5\u9970\u5668\uff08\u5176\u4ed6\u88c5\u9970\u5668\u5c06\u9075\u5faa\u540c\u6837\u7684\u903b\u8f91\uff09\u3002<\/li>\n<\/ul>\n<h2>\u4f7f\u7528 func.call \u8bbe\u5b9a\u4e0a\u4e0b\u6587<\/h2>\n<p>\u4e0a\u9762\u63d0\u5230\u7684\u7f13\u5b58\u88c5\u9970\u5668\u4e0d\u9002\u7528\u4e8e\u5bf9\u8c61\u65b9\u6cd5\u3002<\/p>\n<pre><code class=\"language-js\">\/\/ \u6211\u4eec\u5c06\u5bf9 worker.slow \u7684\u7ed3\u679c\u8fdb\u884c\u7f13\u5b58\nlet worker = {\n  someMethod() {\n    return 1;\n  },\n\n  slow(x) {\n    \/\/ \u53ef\u6015\u7684 CPU \u8fc7\u8f7d\u4efb\u52a1\n    alert(&quot;Called with &quot; + x);\n    return x * this.someMethod(); \/\/ (*)\n  }\n};\n\n\/\/ \u548c\u4e4b\u524d\u4f8b\u5b50\u4e2d\u7684\u4ee3\u7801\u76f8\u540c\nfunction cachingDecorator(func) {\n  let cache = new Map();\n  return function(x) {\n    if (cache.has(x)) {\n      return cache.get(x);\n    }\n    let result = func(x); \/\/ (**)\n    cache.set(x, result);\n    return result;\n  };\n}\n\nalert( worker.slow(1) ); \/\/ \u539f\u59cb\u65b9\u6cd5\u6709\u6548\n\nworker.slow = cachingDecorator(worker.slow); \/\/ \u73b0\u5728\u5bf9\u5176\u8fdb\u884c\u7f13\u5b58\n\nalert( worker.slow(2) ); \/\/ \u86e4\uff01Error: Cannot read property 'someMethod' of undefined\n<\/code><\/pre>\n<p>\u9519\u8bef\u53d1\u751f\u5728\u8bd5\u56fe\u8bbf\u95ee\u00a0<code>this.someMethod<\/code>\u00a0\u5e76\u5931\u8d25\u4e86\u7684\u00a0<code>(*)<\/code>\u00a0\u884c\u4e2d\u3002\u4f60\u80fd\u770b\u51fa\u6765\u4e3a\u4ec0\u4e48\u5417\uff1f<br \/>\n\u539f\u56e0\u662f\u5305\u88c5\u5668\u5c06\u539f\u59cb\u51fd\u6570\u8c03\u7528\u4e3a\u00a0<code>(**)<\/code>\u00a0\u884c\u4e2d\u7684\u00a0<code>func(x)<\/code>\u3002\u5e76\u4e14\uff0c\u5f53\u8fd9\u6837\u8c03\u7528\u65f6\uff0c\u51fd\u6570\u5c06\u5f97\u5230\u00a0<code>this = undefined<\/code>\u3002<br \/>\n\u5305\u88c5\u5668\u5c06\u8c03\u7528\u4f20\u9012\u7ed9\u539f\u59cb\u65b9\u6cd5\uff0c\u4f46\u6ca1\u6709\u4e0a\u4e0b\u6587\u00a0<code>this<\/code>\u3002\u56e0\u6b64\uff0c\u53d1\u751f\u4e86\u9519\u8bef\u3002<br \/>\n\u8ba9\u6211\u4eec\u6765\u89e3\u51b3\u8fd9\u4e2a\u95ee\u9898\u3002<br \/>\n\u6709\u4e00\u4e2a\u7279\u6b8a\u7684\u5185\u5efa\u51fd\u6570\u65b9\u6cd5\u00a0<a href=\"https:\/\/developer.mozilla.org\/zh\/docs\/Web\/JavaScript\/Reference\/Global_Objects\/Function\/call\">func.call(context, \u2026args)<\/a>\uff0c\u5b83\u5141\u8bb8\u8c03\u7528\u4e00\u4e2a\u663e\u5f0f\u8bbe\u7f6e\u00a0<code>this<\/code>\u00a0\u7684\u51fd\u6570\u3002<br \/>\n\u8bed\u6cd5\u5982\u4e0b\uff1a<\/p>\n<pre><code class=\"language-js\">func.call(context, arg1, arg2, ...)\n<\/code><\/pre>\n<p>\u5b83\u8fd0\u884c\u00a0<code>func<\/code>\uff0c\u63d0\u4f9b\u7684\u7b2c\u4e00\u4e2a\u53c2\u6570\u4f5c\u4e3a\u00a0<code>this<\/code>\uff0c\u540e\u9762\u7684\u4f5c\u4e3a\u53c2\u6570\uff08arguments\uff09\u3002<br \/>\n\u7b80\u5355\u5730\u8bf4\uff0c\u8fd9\u4e24\u4e2a\u8c03\u7528\u51e0\u4e4e\u76f8\u540c\uff1a<\/p>\n<pre><code class=\"language-js\">func(1, 2, 3);\nfunc.call(obj, 1, 2, 3)\n<\/code><\/pre>\n<p>\u5b83\u4eec\u8c03\u7528\u7684\u90fd\u662f\u00a0<code>func<\/code>\uff0c\u53c2\u6570\u662f\u00a0<code>1<\/code>\u3001<code>2<\/code>\u00a0\u548c\u00a0<code>3<\/code>\u3002\u552f\u4e00\u7684\u533a\u522b\u662f\u00a0<code>func.call<\/code>\u00a0\u8fd8\u4f1a\u5c06\u00a0<code>this<\/code>\u00a0\u8bbe\u7f6e\u4e3a\u00a0<code>obj<\/code>\u3002<\/p>\n<pre><code class=\"language-js\">let worker = {\n  someMethod() {\n    return 1;\n  },\n\n  slow(x) {\n    alert(&quot;Called with &quot; + x);\n    return x * this.someMethod(); \/\/ (*)\n  }\n};\n\nfunction cachingDecorator(func) {\n  let cache = new Map();\n  return function(x) {\n    if (cache.has(x)) {\n      return cache.get(x);\n    }\n    let result = func.call(this, x); \/\/ \u73b0\u5728 &quot;this&quot; \u88ab\u6b63\u786e\u5730\u4f20\u9012\u4e86\n    cache.set(x, result);\n    return result;\n  };\n}\n\nworker.slow = cachingDecorator(worker.slow); \/\/ \u73b0\u5728\u5bf9\u5176\u8fdb\u884c\u7f13\u5b58\n\nalert( worker.slow(2) ); \/\/ \u5de5\u4f5c\u6b63\u5e38\nalert( worker.slow(2) ); \/\/ \u5de5\u4f5c\u6b63\u5e38\uff0c\u6ca1\u6709\u8c03\u7528\u539f\u59cb\u51fd\u6570\uff08\u4f7f\u7528\u7684\u7f13\u5b58\uff09\n<\/code><\/pre>\n<p>\u73b0\u5728\u4e00\u5207\u90fd\u6b63\u5e38\u5de5\u4f5c\u4e86\u3002<br \/>\n\u4e3a\u4e86\u8ba9\u5927\u5bb6\u7406\u89e3\u5730\u66f4\u6e05\u6670\u4e00\u4e9b\uff0c\u8ba9\u6211\u4eec\u66f4\u6df1\u5165\u5730\u770b\u770b\u00a0<code>this<\/code>\u00a0\u662f\u5982\u4f55\u88ab\u4f20\u9012\u7684\uff1a<\/p>\n<ol>\n<li>\u5728\u7ecf\u8fc7\u88c5\u9970\u4e4b\u540e\uff0c<code>worker.slow<\/code>\u00a0\u73b0\u5728\u662f\u5305\u88c5\u5668\u00a0<code>function (x) { ... }<\/code>\u3002<\/li>\n<li>\u56e0\u6b64\uff0c\u5f53\u00a0<code>worker.slow(2)<\/code>\u00a0\u6267\u884c\u65f6\uff0c\u5305\u88c5\u5668\u5c06\u00a0<code>2<\/code>\u00a0\u4f5c\u4e3a\u53c2\u6570\uff0c\u5e76\u4e14\u00a0<code>this=worker<\/code>\uff08\u5b83\u662f\u70b9\u7b26\u53f7\u00a0<code>.<\/code>\u00a0\u4e4b\u524d\u7684\u5bf9\u8c61\uff09\u3002<\/li>\n<li>\u5728\u5305\u88c5\u5668\u5185\u90e8\uff0c\u5047\u8bbe\u7ed3\u679c\u5c1a\u672a\u7f13\u5b58\uff0c<code>func.call(this, x)<\/code>\u00a0\u5c06\u5f53\u524d\u7684\u00a0<code>this<\/code>\uff08<code>=worker<\/code>\uff09\u548c\u5f53\u524d\u7684\u53c2\u6570\uff08<code>=2<\/code>\uff09\u4f20\u9012\u7ed9\u539f\u59cb\u65b9\u6cd5\u3002<\/li>\n<\/ol>\n<h2>\u4f20\u9012\u591a\u4e2a\u53c2\u6570<\/h2>\n<p>\u73b0\u5728\u8ba9\u6211\u4eec\u628a\u00a0<code>cachingDecorator<\/code>\u00a0\u5199\u5f97\u66f4\u52a0\u901a\u7528\u3002\u5230\u73b0\u5728\u4e3a\u6b62\uff0c\u5b83\u53ea\u80fd\u7528\u4e8e\u5355\u53c2\u6570\u51fd\u6570\u3002<br \/>\n\u73b0\u5728\u5982\u4f55\u7f13\u5b58\u591a\u53c2\u6570\u00a0<code>worker.slow<\/code>\u00a0\u65b9\u6cd5\u5462\uff1f<\/p>\n<pre><code class=\"language-js\">let worker = {\n  slow(min, max) {\n    return min + max; \/\/ scary CPU-hogger is assumed\n  }\n};\n\n\/\/ \u5e94\u8be5\u8bb0\u4f4f\u76f8\u540c\u53c2\u6570\u7684\u8c03\u7528\nworker.slow = cachingDecorator(worker.slow);\n<\/code><\/pre>\n<p>\u4e4b\u524d\uff0c\u5bf9\u4e8e\u5355\u4e2a\u53c2\u6570\u00a0<code>x<\/code>\uff0c\u6211\u4eec\u53ef\u4ee5\u53ea\u4f7f\u7528\u00a0<code>cache.set(x, result)<\/code>\u00a0\u6765\u4fdd\u5b58\u7ed3\u679c\uff0c\u5e76\u4f7f\u7528\u00a0<code>cache.get(x)<\/code>\u00a0\u6765\u68c0\u7d22\u5e76\u83b7\u53d6\u7ed3\u679c\u3002\u4f46\u662f\u73b0\u5728\uff0c\u6211\u4eec\u9700\u8981\u8bb0\u4f4f\u00a0<strong>\u53c2\u6570\u7ec4\u5408<\/strong>\u00a0<code>(min,max)<\/code>\u00a0\u7684\u7ed3\u679c\u3002\u539f\u751f\u7684\u00a0<code>Map<\/code>\u00a0\u4ec5\u5c06\u5355\u4e2a\u503c\u4f5c\u4e3a\u952e\uff08key\uff09\u3002<br \/>\n\u8fd9\u513f\u6709\u8bb8\u591a\u89e3\u51b3\u65b9\u6848\u53ef\u4ee5\u5b9e\u73b0\uff1a<\/p>\n<ol>\n<li>\u5b9e\u73b0\u4e00\u4e2a\u65b0\u7684\uff08\u6216\u4f7f\u7528\u7b2c\u4e09\u65b9\u7684\uff09\u7c7b\u4f3c map \u7684\u66f4\u901a\u7528\u5e76\u4e14\u5141\u8bb8\u591a\u4e2a\u952e\u7684\u6570\u636e\u7ed3\u6784\u3002<\/li>\n<li>\u4f7f\u7528\u5d4c\u5957 map\uff1a<code>cache.set(min)<\/code>\u00a0\u5c06\u662f\u4e00\u4e2a\u5b58\u50a8\uff08\u952e\u503c\uff09\u5bf9\u00a0<code>(max, result)<\/code>\u00a0\u7684\u00a0<code>Map<\/code>\u3002\u6240\u4ee5\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u00a0<code>cache.get(min).get(max)<\/code>\u00a0\u6765\u83b7\u53d6\u00a0<code>result<\/code>\u3002<\/li>\n<li>\u5c06\u4e24\u4e2a\u503c\u5408\u5e76\u4e3a\u4e00\u4e2a\u3002\u4e3a\u4e86\u7075\u6d3b\u6027\uff0c\u6211\u4eec\u53ef\u4ee5\u5141\u8bb8\u4e3a\u88c5\u9970\u5668\u63d0\u4f9b\u4e00\u4e2a\u201c\u54c8\u5e0c\u51fd\u6570\u201d\uff0c\u8be5\u51fd\u6570\u77e5\u9053\u5982\u4f55\u5c06\u591a\u4e2a\u503c\u5408\u5e76\u4e3a\u4e00\u4e2a\u503c\u3002<br \/>\n\u5bf9\u4e8e\u8bb8\u591a\u5b9e\u9645\u5e94\u7528\uff0c\u7b2c\u4e09\u79cd\u65b9\u5f0f\u5c31\u8db3\u591f\u4e86\uff0c\u6240\u4ee5\u6211\u4eec\u5c31\u7528\u8fd9\u4e2a\u5427\u3002<br \/>\n\u5f53\u7136\uff0c\u6211\u4eec\u9700\u8981\u4f20\u5165\u7684\u4e0d\u4ec5\u662f\u00a0<code>x<\/code>\uff0c\u8fd8\u9700\u8981\u4f20\u5165\u00a0<code>func.call<\/code>\u00a0\u7684\u6240\u6709\u53c2\u6570\u3002\u8ba9\u6211\u4eec\u56de\u60f3\u4e00\u4e0b\uff0c\u5728\u00a0<code>function()<\/code>\u00a0\u4e2d\u6211\u4eec\u53ef\u4ee5\u5f97\u5230\u4e00\u4e2a\u5305\u542b\u6240\u6709\u53c2\u6570\u7684\u4f2a\u6570\u7ec4\uff08pseudo-array\uff09<code>arguments<\/code>\uff0c\u90a3\u4e48\u00a0<code>func.call(this, x)<\/code>\u00a0\u5e94\u8be5\u88ab\u66ff\u6362\u4e3a\u00a0<code>func.call(this, ...arguments)<\/code>\u3002<br \/>\n\u8fd9\u662f\u4e00\u4e2a\u66f4\u5f3a\u5927\u7684\u00a0<code>cachingDecorator<\/code>\uff1a<\/li>\n<\/ol>\n<pre><code class=\"language-js\">let worker = {\n  slow(min, max) {\n    alert(`Called with ${min},${max}`);\n    return min + max;\n  }\n};\n\nfunction cachingDecorator(func, hash) {\n  let cache = new Map();\n  return function() {\n    let key = hash(arguments); \/\/ (*)\n    if (cache.has(key)) {\n      return cache.get(key);\n    }\n\n    let result = func.call(this, ...arguments); \/\/ (**)\n\n    cache.set(key, result);\n    return result;\n  };\n}\n\nfunction hash(args) {\n  return args[0] + ',' + args[1];\n}\n\nworker.slow = cachingDecorator(worker.slow, hash);\n\nalert( worker.slow(3, 5) ); \/\/ works\nalert( &quot;Again &quot; + worker.slow(3, 5) ); \/\/ same (cached)\n<\/code><\/pre>\n<p>\u73b0\u5728\u8fd9\u4e2a\u5305\u88c5\u5668\u53ef\u4ee5\u5904\u7406\u4efb\u610f\u6570\u91cf\u7684\u53c2\u6570\u4e86\uff08\u5c3d\u7ba1\u54c8\u5e0c\u51fd\u6570\u8fd8\u9700\u8981\u88ab\u8fdb\u884c\u8c03\u6574\u4ee5\u5141\u8bb8\u4efb\u610f\u6570\u91cf\u7684\u53c2\u6570\u3002\u4e00\u79cd\u6709\u8da3\u7684\u5904\u7406\u65b9\u6cd5\u5c06\u5728\u4e0b\u9762\u8bb2\u5230\uff09\u3002<br \/>\n\u8fd9\u91cc\u6709\u4e24\u4e2a\u53d8\u5316\uff1a<\/p>\n<ul>\n<li>\u5728\u00a0<code>(*)<\/code>\u00a0\u884c\u4e2d\u5b83\u8c03\u7528\u00a0<code>hash<\/code>\u00a0\u6765\u4ece\u00a0<code>arguments<\/code>\u00a0\u521b\u5efa\u4e00\u4e2a\u5355\u72ec\u7684\u952e\u3002\u8fd9\u91cc\u6211\u4eec\u4f7f\u7528\u4e00\u4e2a\u7b80\u5355\u7684\u201c\u8fde\u63a5\u201d\u51fd\u6570\uff0c\u5c06\u53c2\u6570\u00a0<code>(3, 5)<\/code>\u00a0\u8f6c\u6362\u4e3a\u952e\u00a0<code>&quot;3,5&quot;<\/code>\u3002\u66f4\u590d\u6742\u7684\u60c5\u51b5\u53ef\u80fd\u9700\u8981\u5176\u4ed6\u54c8\u5e0c\u51fd\u6570\u3002<\/li>\n<li>\u7136\u540e\u00a0<code>(**)<\/code>\u00a0\u884c\u4f7f\u7528\u00a0<code>func.call(this, ...arguments)<\/code>\u00a0\u5c06\u5305\u88c5\u5668\u83b7\u5f97\u7684\u4e0a\u4e0b\u6587\u548c\u6240\u6709\u53c2\u6570\uff08\u4e0d\u4ec5\u4ec5\u662f\u7b2c\u4e00\u4e2a\u53c2\u6570\uff09\u4f20\u9012\u7ed9\u539f\u59cb\u51fd\u6570\u3002<\/li>\n<\/ul>\n<h2>func.apply<\/h2>\n<p>\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u00a0<code>func.apply(this, arguments)<\/code>\u00a0\u4ee3\u66ff\u00a0<code>func.call(this, ...arguments)<\/code>\u3002<br \/>\n\u5185\u5efa\u65b9\u6cd5\u00a0<a href=\"https:\/\/developer.mozilla.org\/zh\/docs\/Web\/JavaScript\/Reference\/Global_Objects\/Function\/apply\">func.apply<\/a>\u00a0\u7684\u8bed\u6cd5\u662f\uff1a<\/p>\n<pre><code class=\"language-js\">func.apply(context, args)\n<\/code><\/pre>\n<p>\u5b83\u8fd0\u884c\u00a0<code>func<\/code>\u00a0\u8bbe\u7f6e\u00a0<code>this=context<\/code>\uff0c\u5e76\u4f7f\u7528\u7c7b\u6570\u7ec4\u5bf9\u8c61\u00a0<code>args<\/code>\u00a0\u4f5c\u4e3a\u53c2\u6570\u5217\u8868\uff08arguments\uff09\u3002<br \/>\n<code>call<\/code>\u00a0\u548c\u00a0<code>apply<\/code>\u00a0\u4e4b\u95f4\u552f\u4e00\u7684\u8bed\u6cd5\u533a\u522b\u662f\uff0c<code>call<\/code>\u00a0\u671f\u671b\u4e00\u4e2a\u53c2\u6570\u5217\u8868\uff0c\u800c\u00a0<code>apply<\/code>\u00a0\u671f\u671b\u4e00\u4e2a\u5305\u542b\u8fd9\u4e9b\u53c2\u6570\u7684\u7c7b\u6570\u7ec4\u5bf9\u8c61\u3002<br \/>\n\u56e0\u6b64\uff0c\u8fd9\u4e24\u4e2a\u8c03\u7528\u51e0\u4e4e\u662f\u7b49\u6548\u7684\uff1a<\/p>\n<pre><code class=\"language-js\">func.call(context, ...args);\nfunc.apply(context, args);\n<\/code><\/pre>\n<p>\u5b83\u4eec\u4f7f\u7528\u7ed9\u5b9a\u7684\u4e0a\u4e0b\u6587\u548c\u53c2\u6570\u6267\u884c\u76f8\u540c\u7684\u00a0<code>func<\/code>\u00a0\u8c03\u7528\u3002<br \/>\n\u53ea\u6709\u4e00\u4e2a\u5173\u4e8e\u00a0<code>args<\/code>\u00a0\u7684\u7ec6\u5fae\u7684\u5dee\u522b\uff1a<\/p>\n<ul>\n<li>Spread \u8bed\u6cd5\u00a0<code>...<\/code>\u00a0\u5141\u8bb8\u5c06\u00a0<strong>\u53ef\u8fed\u4ee3\u5bf9\u8c61<\/strong>\u00a0<code>args<\/code>\u00a0\u4f5c\u4e3a\u5217\u8868\u4f20\u9012\u7ed9\u00a0<code>call<\/code>\u3002<\/li>\n<li><code>apply<\/code>\u00a0\u53ea\u63a5\u53d7\u00a0<strong>\u7c7b\u6570\u7ec4<\/strong>\u00a0<code>args<\/code>\u3002<br \/>\n\u2026\u2026\u5bf9\u4e8e\u5373\u53ef\u8fed\u4ee3\u53c8\u662f\u7c7b\u6570\u7ec4\u7684\u5bf9\u8c61\uff0c\u4f8b\u5982\u4e00\u4e2a\u771f\u6b63\u7684\u6570\u7ec4\uff0c\u6211\u4eec\u4f7f\u7528\u00a0<code>call<\/code>\u00a0\u6216\u00a0<code>apply<\/code>\u00a0\u5747\u53ef\uff0c\u4f46\u662f\u00a0<code>apply<\/code>\u00a0\u53ef\u80fd\u4f1a\u66f4\u5feb\uff0c\u56e0\u4e3a\u5927\u591a\u6570 JavaScript \u5f15\u64ce\u5728\u5185\u90e8\u5bf9\u5176\u8fdb\u884c\u4e86\u4f18\u5316\u3002<br \/>\n\u5c06\u6240\u6709\u53c2\u6570\u8fde\u540c\u4e0a\u4e0b\u6587\u4e00\u8d77\u4f20\u9012\u7ed9\u53e6\u4e00\u4e2a\u51fd\u6570\u88ab\u79f0\u4e3a\u201c\u547c\u53eb\u8f6c\u79fb\uff08call forwarding\uff09\u201d\u3002<br \/>\n\u8fd9\u662f\u5b83\u7684\u6700\u7b80\u5f62\u5f0f\uff1a<\/li>\n<\/ul>\n<pre><code class=\"language-js\">let wrapper = function() {\n  return func.apply(this, arguments);\n};\n<\/code><\/pre>\n<p>\u5f53\u5916\u90e8\u4ee3\u7801\u8c03\u7528\u8fd9\u79cd\u5305\u88c5\u5668\u00a0<code>wrapper<\/code>\u00a0\u65f6\uff0c\u5b83\u4e0e\u539f\u59cb\u51fd\u6570\u00a0<code>func<\/code>\u00a0\u7684\u8c03\u7528\u662f\u65e0\u6cd5\u533a\u5206\u7684\u3002<\/p>\n<h2>\u501f\u7528\u4e00\u79cd\u65b9\u6cd5<\/h2>\n<p>\u73b0\u5728\uff0c\u8ba9\u6211\u4eec\u5bf9\u54c8\u5e0c\u51fd\u6570\u518d\u505a\u4e00\u4e2a\u8f83\u5c0f\u7684\u6539\u8fdb\uff0c\u622a\u81f3\u76ee\u524d\uff0c\u5b83\u4ec5\u9002\u7528\u4e8e\u4e24\u4e2a\u53c2\u6570\u3002\u5982\u679c\u5b83\u53ef\u4ee5\u9002\u7528\u4e8e\u4efb\u4f55\u6570\u91cf\u7684\u00a0<code>args<\/code>\u00a0\u5c31\u66f4\u597d\u4e86\u3002<br \/>\n\u81ea\u7136\u7684\u89e3\u51b3\u65b9\u6848\u662f\u4f7f\u7528\u00a0<a href=\"https:\/\/developer.mozilla.org\/zh\/docs\/Web\/JavaScript\/Reference\/Global_Objects\/Array\/join\">arr.join<\/a>\u00a0\u65b9\u6cd5\uff1a<br \/>\n\u2026\u2026\u4e0d\u5e78\u7684\u662f\uff0c\u8fd9\u4e0d\u884c\u3002\u56e0\u4e3a\u6211\u4eec\u6b63\u5728\u8c03\u7528\u00a0<code>hash(arguments)<\/code>\uff0c<code>arguments<\/code>\u00a0\u5bf9\u8c61\u65e2\u662f\u53ef\u8fed\u4ee3\u5bf9\u8c61\u53c8\u662f\u7c7b\u6570\u7ec4\u5bf9\u8c61\uff0c\u4f46\u5b83\u5e76\u4e0d\u662f\u771f\u6b63\u7684\u6570\u7ec4\u3002<br \/>\n\u6240\u4ee5\u5728\u5b83\u4e0a\u9762\u8c03\u7528\u00a0<code>join<\/code>\u00a0\u4f1a\u5931\u8d25<br \/>\n\u4e0d\u8fc7\uff0c\u6709\u4e00\u79cd\u7b80\u5355\u7684\u65b9\u6cd5\u53ef\u4ee5\u4f7f\u7528\u6570\u7ec4\u7684 join \u65b9\u6cd5\uff1a<\/p>\n<pre><code class=\"language-js\">function hash() {\n  alert( [].join.call(arguments) ); \/\/ 1,2\n}\n\nhash(1, 2);\n<\/code><\/pre>\n<p>\u8fd9\u4e2a\u6280\u5de7\u88ab\u79f0\u4e3a\u00a0<strong>\u65b9\u6cd5\u501f\u7528\uff08method borrowing\uff09<\/strong>\u3002<br \/>\n\u6211\u4eec\u4ece\u5e38\u89c4\u6570\u7ec4\u00a0<code>[].join<\/code>\u00a0\u4e2d\u83b7\u53d6\uff08\u501f\u7528\uff09join \u65b9\u6cd5\uff0c\u5e76\u4f7f\u7528\u00a0<code>[].join.call<\/code>\u00a0\u5728\u00a0<code>arguments<\/code>\u00a0\u7684\u4e0a\u4e0b\u6587\u4e2d\u8fd0\u884c\u5b83\u3002<br \/>\n\u5b83\u4e3a\u4ec0\u4e48\u6709\u6548\uff1f<br \/>\n\u90a3\u662f\u56e0\u4e3a\u539f\u751f\u65b9\u6cd5\u00a0<code>arr.join(glue)<\/code>\u00a0\u7684\u5185\u90e8\u7b97\u6cd5\u975e\u5e38\u7b80\u5355\u3002<br \/>\n\u4ece\u89c4\u8303\u4e2d\u51e0\u4e4e\u201c\u6309\u539f\u6837\u201d\u89e3\u91ca\u5982\u4e0b\uff1a<\/p>\n<ol>\n<li>\u8ba9\u00a0<code>glue<\/code>\u00a0\u6210\u4e3a\u7b2c\u4e00\u4e2a\u53c2\u6570\uff0c\u5982\u679c\u6ca1\u6709\u53c2\u6570\uff0c\u5219\u4f7f\u7528\u9017\u53f7\u00a0<code>&quot;,&quot;<\/code>\u3002<\/li>\n<li>\u8ba9\u00a0<code>result<\/code>\u00a0\u4e3a\u7a7a\u5b57\u7b26\u4e32\u3002<\/li>\n<li>\u5c06\u00a0<code>this[0]<\/code>\u00a0\u9644\u52a0\u5230\u00a0<code>result<\/code>\u3002<\/li>\n<li>\u9644\u52a0\u00a0<code>glue<\/code>\u00a0\u548c\u00a0<code>this[1]<\/code>\u3002<\/li>\n<li>\u9644\u52a0\u00a0<code>glue<\/code>\u00a0\u548c\u00a0<code>this[2]<\/code>\u3002<\/li>\n<li>\u2026\u2026\u4ee5\u6b64\u7c7b\u63a8\uff0c\u76f4\u5230\u00a0<code>this.length<\/code>\u00a0\u9879\u76ee\u88ab\u7c98\u5728\u4e00\u8d77\u3002<\/li>\n<li>\u8fd4\u56de\u00a0<code>result<\/code>\u3002<br \/>\n\u56e0\u6b64\uff0c\u4ece\u6280\u672f\u4e0a\u8bb2\uff0c\u5b83\u9700\u8981\u00a0<code>this<\/code>\u00a0\u5e76\u5c06\u00a0<code>this[0]<\/code>\uff0c<code>this[1]<\/code>\u00a0\u2026\u2026\u7b49 join \u5728\u4e00\u8d77\u3002\u5b83\u7684\u7f16\u5199\u65b9\u5f0f\u662f\u6545\u610f\u5141\u8bb8\u4efb\u4f55\u7c7b\u6570\u7ec4\u7684\u00a0<code>this<\/code>\u00a0\u7684\uff08\u4e0d\u662f\u5de7\u5408\uff0c\u5f88\u591a\u65b9\u6cd5\u90fd\u9075\u5faa\u8fd9\u79cd\u505a\u6cd5\uff09\u3002\u8fd9\u5c31\u662f\u4e3a\u4ec0\u4e48\u5b83\u4e5f\u53ef\u4ee5\u548c\u00a0<code>this=arguments<\/code>\u00a0\u4e00\u8d77\u4f7f\u7528\u3002<\/li>\n<\/ol>\n<h2>\u88c5\u9970\u5668\u548c\u51fd\u6570\u5c5e\u6027<\/h2>\n<p>\u901a\u5e38\uff0c\u7528\u88c5\u9970\u7684\u51fd\u6570\u66ff\u6362\u4e00\u4e2a\u51fd\u6570\u6216\u4e00\u4e2a\u65b9\u6cd5\u662f\u5b89\u5168\u7684\uff0c\u9664\u4e86\u4e00\u4ef6\u5c0f\u4e1c\u897f\u3002\u5982\u679c\u539f\u59cb\u51fd\u6570\u6709\u5c5e\u6027\uff0c\u4f8b\u5982\u00a0<code>func.calledCount<\/code>\u00a0\u6216\u5176\u4ed6\uff0c\u5219\u88c5\u9970\u540e\u7684\u51fd\u6570\u5c06\u4e0d\u518d\u63d0\u4f9b\u8fd9\u4e9b\u5c5e\u6027\u3002\u56e0\u4e3a\u8fd9\u662f\u88c5\u9970\u5668\u3002\u56e0\u6b64\uff0c\u5982\u679c\u6709\u4eba\u4f7f\u7528\u5b83\u4eec\uff0c\u90a3\u4e48\u5c31\u9700\u8981\u5c0f\u5fc3\u3002<br \/>\n\u4f8b\u5982\uff0c\u5728\u4e0a\u9762\u7684\u793a\u4f8b\u4e2d\uff0c\u5982\u679c\u00a0<code>slow<\/code>\u00a0\u51fd\u6570\u5177\u6709\u4efb\u4f55\u5c5e\u6027\uff0c\u800c\u00a0<code>cachingDecorator(slow)<\/code>\u00a0\u5219\u662f\u4e00\u4e2a\u6ca1\u6709\u8fd9\u4e9b\u5c5e\u6027\u7684\u5305\u88c5\u5668\u3002<br \/>\n\u4e00\u4e9b\u5305\u88c5\u5668\u53ef\u80fd\u4f1a\u63d0\u4f9b\u81ea\u5df1\u7684\u5c5e\u6027\u3002\u4f8b\u5982\uff0c\u88c5\u9970\u5668\u4f1a\u8ba1\u7b97\u4e00\u4e2a\u51fd\u6570\u88ab\u8c03\u7528\u4e86\u591a\u5c11\u6b21\u4ee5\u53ca\u82b1\u8d39\u4e86\u591a\u5c11\u65f6\u95f4\uff0c\u5e76\u901a\u8fc7\u5305\u88c5\u5668\u5c5e\u6027\u516c\u5f00\uff08expose\uff09\u8fd9\u4e9b\u4fe1\u606f\u3002<br \/>\n\u5b58\u5728\u4e00\u79cd\u521b\u5efa\u88c5\u9970\u5668\u7684\u65b9\u6cd5\uff0c\u8be5\u88c5\u9970\u5668\u53ef\u4fdd\u7559\u5bf9\u51fd\u6570\u5c5e\u6027\u7684\u8bbf\u95ee\u6743\u9650\uff0c\u4f46\u8fd9\u9700\u8981\u4f7f\u7528\u7279\u6b8a\u7684\u00a0<code>Proxy<\/code>\u00a0\u5bf9\u8c61\u6765\u5305\u88c5\u51fd\u6570\u3002\u6211\u4eec\u5c06\u5728\u540e\u9762\u7684\u00a0<a href=\"https:\/\/zh.javascript.info\/proxy#proxy-apply\">Proxy \u548c Reflect<\/a>\u00a0\u4e2d\u5b66\u4e60\u5b83\u3002<\/p>\n<h1>\u51fd\u6570\u7ed1\u5b9a<\/h1>\n<p>\u5f53\u5c06\u5bf9\u8c61\u65b9\u6cd5\u4f5c\u4e3a\u56de\u8c03\u8fdb\u884c\u4f20\u9012\uff0c\u4f8b\u5982\u4f20\u9012\u7ed9\u00a0<code>setTimeout<\/code>\uff0c\u8fd9\u513f\u4f1a\u5b58\u5728\u4e00\u4e2a\u5e38\u89c1\u7684\u95ee\u9898\uff1a\u201c\u4e22\u5931\u00a0<code>this<\/code>\u201d\u3002<\/p>\n<h2>\u4e22\u5931 this<\/h2>\n<p>\u6211\u4eec\u5df2\u7ecf\u770b\u5230\u4e86\u4e22\u5931\u00a0<code>this<\/code>\u00a0\u7684\u4f8b\u5b50\u3002\u4e00\u65e6\u65b9\u6cd5\u88ab\u4f20\u9012\u5230\u4e0e\u5bf9\u8c61\u5206\u5f00\u7684\u67d0\u4e2a\u5730\u65b9 \u2014\u2014\u00a0<code>this<\/code>\u00a0\u5c31\u4e22\u5931\u3002<br \/>\n\u4e0b\u9762\u662f\u4f7f\u7528\u00a0<code>setTimeout<\/code>\u00a0\u65f6\u00a0<code>this<\/code>\u00a0\u662f\u5982\u4f55\u4e22\u5931\u7684\uff1a<\/p>\n<pre><code class=\"language-js\">let user = {\n  firstName: &quot;John&quot;,\n  sayHi() {\n    alert(`Hello, ${this.firstName}!`);\n  }\n};\n\nsetTimeout(user.sayHi, 1000); \/\/ Hello, undefined!\n<\/code><\/pre>\n<p>\u6b63\u5982\u6211\u4eec\u6240\u770b\u5230\u7684\uff0c\u8f93\u51fa\u6ca1\u6709\u50cf\u00a0<code>this.firstName<\/code>\u00a0\u90a3\u6837\u663e\u793a \u201cJohn\u201d\uff0c\u800c\u663e\u793a\u4e86\u00a0<code>undefined<\/code>\uff01<br \/>\n\u8fd9\u662f\u56e0\u4e3a\u00a0<code>setTimeout<\/code>\u00a0\u83b7\u53d6\u5230\u4e86\u51fd\u6570\u00a0<code>user.sayHi<\/code>\uff0c\u4f46\u5b83\u548c\u5bf9\u8c61\u5206\u79bb\u5f00\u4e86\u3002<br \/>\n\u6d4f\u89c8\u5668\u4e2d\u7684\u00a0<code>setTimeout<\/code>\u00a0\u65b9\u6cd5\u6709\u4e9b\u7279\u6b8a\uff1a\u5b83\u4e3a\u51fd\u6570\u8c03\u7528\u8bbe\u5b9a\u4e86\u00a0<code>this=window<\/code>\uff08\u5bf9\u4e8e Node.js\uff0c<code>this<\/code>\u00a0\u5219\u4f1a\u53d8\u4e3a\u8ba1\u65f6\u5668\uff08timer\uff09\u5bf9\u8c61\uff0c\u4f46\u5728\u8fd9\u513f\u5e76\u4e0d\u91cd\u8981\uff09\u3002\u6240\u4ee5\u5bf9\u4e8e\u00a0<code>this.firstName<\/code>\uff0c\u5b83\u5176\u5b9e\u8bd5\u56fe\u83b7\u53d6\u7684\u662f\u00a0<code>window.firstName<\/code>\uff0c\u8fd9\u4e2a\u53d8\u91cf\u5e76\u4e0d\u5b58\u5728\u3002\u5728\u5176\u4ed6\u7c7b\u4f3c\u7684\u60c5\u51b5\u4e0b\uff0c\u901a\u5e38\u00a0<code>this<\/code>\u00a0\u4f1a\u53d8\u4e3a\u00a0<code>undefined<\/code>\u3002<br \/>\n\u8fd9\u4e2a\u9700\u6c42\u5f88\u5178\u578b \u2014\u2014 \u6211\u4eec\u60f3\u5c06\u4e00\u4e2a\u5bf9\u8c61\u65b9\u6cd5\u4f20\u9012\u5230\u522b\u7684\u5730\u65b9\uff08\u8fd9\u91cc \u2014\u2014 \u4f20\u9012\u5230\u8c03\u5ea6\u7a0b\u5e8f\uff09\uff0c\u7136\u540e\u5728\u8be5\u4f4d\u7f6e\u8c03\u7528\u5b83\u3002\u5982\u4f55\u786e\u4fdd\u5728\u6b63\u786e\u7684\u4e0a\u4e0b\u6587\u4e2d\u8c03\u7528\u5b83\uff1f<\/p>\n<h2>\u89e3\u51b3\u65b9\u68481\uff1a\u5305\u88c5\u5668<\/h2>\n<p>\u6700\u7b80\u5355\u7684\u89e3\u51b3\u65b9\u6848\u662f\u4f7f\u7528\u4e00\u4e2a\u5305\u88c5\u51fd\u6570<\/p>\n<pre><code class=\"language-js\">let user = {\n  firstName: &quot;John&quot;,\n  sayHi() {\n    alert(`Hello, ${this.firstName}!`);\n  }\n};\n\nsetTimeout(function() {\n  user.sayHi(); \/\/ Hello, John!\n}, 1000);\n\nsetTimeout(() =&gt; user.sayHi(), 1000); \/\/ Hello, John!\n<\/code><\/pre>\n<p>\u770b\u8d77\u6765\u4e0d\u9519\uff0c\u4f46\u662f\u6211\u4eec\u7684\u4ee3\u7801\u7ed3\u6784\u4e2d\u51fa\u73b0\u4e86\u4e00\u4e2a\u5c0f\u6f0f\u6d1e\u3002<br \/>\n\u5982\u679c\u5728\u00a0<code>setTimeout<\/code>\u00a0\u89e6\u53d1\u4e4b\u524d\uff08\u6709\u4e00\u79d2\u7684\u5ef6\u8fdf\uff01\uff09<code>user<\/code>\u00a0\u7684\u503c\u6539\u53d8\u4e86\u600e\u4e48\u529e\uff1f\u90a3\u4e48\uff0c\u7a81\u7136\u95f4\uff0c\u5b83\u5c06\u8c03\u7528\u9519\u8bef\u7684\u5bf9\u8c61\uff01<br \/>\n\u4e0b\u4e00\u4e2a\u89e3\u51b3\u65b9\u6848\u4fdd\u8bc1\u4e86\u8fd9\u6837\u7684\u4e8b\u60c5\u4e0d\u4f1a\u53d1\u751f\u3002<\/p>\n<h2>\u89e3\u51b3\u65b9\u68482\uff1abind<\/h2>\n<p>\u51fd\u6570\u63d0\u4f9b\u4e86\u4e00\u4e2a\u5185\u5efa\u65b9\u6cd5\u00a0<a href=\"https:\/\/developer.mozilla.org\/zh\/docs\/Web\/JavaScript\/Reference\/Global_Objects\/Function\/bind\">bind<\/a>\uff0c\u5b83\u53ef\u4ee5\u7ed1\u5b9a\u00a0<code>this<\/code>\u3002<br \/>\n\u57fa\u672c\u7684\u8bed\u6cd5\u662f\uff1a<\/p>\n<pre><code class=\"language-js\">\/\/ \u7a0d\u540e\u5c06\u4f1a\u6709\u66f4\u590d\u6742\u7684\u8bed\u6cd5\nlet boundFunc = func.bind(context);\n<\/code><\/pre>\n<p><code>func.bind(context)<\/code>\u00a0\u7684\u7ed3\u679c\u662f\u4e00\u4e2a\u7279\u6b8a\u7684\u7c7b\u4f3c\u4e8e\u51fd\u6570\u7684\u201c\u5916\u6765\u5bf9\u8c61\uff08exotic object\uff09\u201d\uff0c\u5b83\u53ef\u4ee5\u50cf\u51fd\u6570\u4e00\u6837\u88ab\u8c03\u7528\uff0c\u5e76\u4e14\u900f\u660e\u5730\uff08transparently\uff09\u5c06\u8c03\u7528\u4f20\u9012\u7ed9\u00a0<code>func<\/code>\u00a0\u5e76\u8bbe\u5b9a\u00a0<code>this=context<\/code>\u3002<br \/>\n\u6362\u53e5\u8bdd\u8bf4\uff0c<code>boundFunc<\/code>\u00a0\u8c03\u7528\u5c31\u50cf\u7ed1\u5b9a\u4e86\u00a0<code>this<\/code>\u00a0\u7684\u00a0<code>func<\/code>\u3002<br \/>\n\u4e3e\u4e2a\u4f8b\u5b50\uff0c\u8fd9\u91cc\u7684\u00a0<code>funcUser<\/code>\u00a0\u5c06\u8c03\u7528\u4f20\u9012\u7ed9\u4e86\u00a0<code>func<\/code>\u00a0\u540c\u65f6\u00a0<code>this=user<\/code>\uff1a<\/p>\n<pre><code class=\"language-js\">let user = {\n  firstName: &quot;John&quot;\n};\n\nfunction func() {\n  alert(this.firstName);\n}\n\nlet funcUser = func.bind(user);\nfuncUser(); \/\/ John\n<\/code><\/pre>\n<p>\u8fd9\u91cc\u7684\u00a0<code>func.bind(user)<\/code>\u00a0\u4f5c\u4e3a\u00a0<code>func<\/code>\u00a0\u7684\u201c\u7ed1\u5b9a\u7684\uff08bound\uff09\u53d8\u4f53\u201d\uff0c\u7ed1\u5b9a\u4e86\u00a0<code>this=user<\/code>\u3002<br \/>\n\u6240\u6709\u7684\u53c2\u6570\uff08arguments\uff09\u90fd\u88ab\u201c\u539f\u6837\u201d\u4f20\u9012\u7ed9\u4e86\u521d\u59cb\u7684\u00a0<code>func<\/code><\/p>\n<pre><code class=\"language-js\">let user = {\n  firstName: &quot;John&quot;,\n  sayHi() {\n    alert(`Hello, ${this.firstName}!`);\n  }\n};\n\nlet sayHi = user.sayHi.bind(user); \/\/ (*)\n\n\/\/ \u53ef\u4ee5\u5728\u6ca1\u6709\u5bf9\u8c61\uff08\u8bd1\u6ce8\uff1a\u4e0e\u5bf9\u8c61\u5206\u79bb\uff09\u7684\u60c5\u51b5\u4e0b\u8fd0\u884c\u5b83\nsayHi(); \/\/ Hello, John!\n\nsetTimeout(sayHi, 1000); \/\/ Hello, John!\n\n\/\/ \u5373\u4f7f user \u7684\u503c\u5728\u4e0d\u5230 1 \u79d2\u5185\u53d1\u751f\u4e86\u6539\u53d8\n\/\/ sayHi \u8fd8\u662f\u4f1a\u4f7f\u7528\u9884\u5148\u7ed1\u5b9a\uff08pre-bound\uff09\u7684\u503c\uff0c\u8be5\u503c\u662f\u5bf9\u65e7\u7684 user \u5bf9\u8c61\u7684\u5f15\u7528\nuser = {\n  sayHi() { alert(&quot;Another user in setTimeout!&quot;); }\n};\n<\/code><\/pre>\n<p>\u5728\u00a0<code>(*)<\/code>\u00a0\u884c\uff0c\u6211\u4eec\u53d6\u4e86\u65b9\u6cd5\u00a0<code>user.sayHi<\/code>\u00a0\u5e76\u5c06\u5176\u7ed1\u5b9a\u5230\u00a0<code>user<\/code>\u3002<code>sayHi<\/code>\u00a0\u662f\u4e00\u4e2a\u201c\u7ed1\u5b9a\u540e\uff08bound\uff09\u201d\u7684\u65b9\u6cd5\uff0c\u5b83\u53ef\u4ee5\u88ab\u5355\u72ec\u8c03\u7528\uff0c\u4e5f\u53ef\u4ee5\u88ab\u4f20\u9012\u7ed9\u00a0<code>setTimeout<\/code>\u00a0\u2014\u2014 \u90fd\u6ca1\u5173\u7cfb\uff0c\u51fd\u6570\u4e0a\u4e0b\u6587\u90fd\u4f1a\u662f\u6b63\u786e\u7684\u3002<br \/>\n\u8fd9\u91cc\u6211\u4eec\u80fd\u591f\u770b\u5230\u53c2\u6570\uff08arguments\uff09\u90fd\u88ab\u201c\u539f\u6837\u201d\u4f20\u9012\u4e86\uff0c\u53ea\u662f\u00a0<code>this<\/code>\u00a0\u88ab\u00a0<code>bind<\/code>\u00a0\u7ed1\u5b9a\u4e86\uff1a<\/p>\n<pre><code class=\"language-js\">let user = {\n  firstName: &quot;John&quot;,\n  say(phrase) {\n    alert(`${phrase}, ${this.firstName}!`);\n  }\n};\n\nlet say = user.say.bind(user);\n\nsay(&quot;Hello&quot;); \/\/ Hello, John!\uff08\u53c2\u6570 &quot;Hello&quot; \u88ab\u4f20\u9012\u7ed9\u4e86 say\uff09\nsay(&quot;Bye&quot;); \/\/ Bye, John!\uff08\u53c2\u6570 &quot;Bye&quot; \u88ab\u4f20\u9012\u7ed9\u4e86 say\uff09\n<\/code><\/pre>\n<blockquote>\n<p>\u4fbf\u6377\u65b9\u6cd5\uff1a<code>bindAll<\/code><br \/>\n\u5982\u679c\u4e00\u4e2a\u5bf9\u8c61\u6709\u5f88\u591a\u65b9\u6cd5\uff0c\u5e76\u4e14\u6211\u4eec\u90fd\u6253\u7b97\u5c06\u5b83\u4eec\u90fd\u4f20\u9012\u51fa\u53bb\uff0c\u90a3\u4e48\u6211\u4eec\u53ef\u4ee5\u5728\u4e00\u4e2a\u5faa\u73af\u4e2d\u5b8c\u6210\u6240\u6709\u65b9\u6cd5\u7684\u7ed1\u5b9a\uff1a<\/p>\n<\/blockquote>\n<pre><code class=\"language-js\">for (let key in user) {\n  if (typeof user[key] == 'function') {\n    user[key] = user[key].bind(user);\n  }\n}\n<\/code><\/pre>\n<p>JavaScript \u5e93\u8fd8\u63d0\u4f9b\u4e86\u65b9\u4fbf\u6279\u91cf\u7ed1\u5b9a\u7684\u51fd\u6570\uff0c\u4f8b\u5982 lodash \u4e2d\u7684\u00a0<a href=\"http:\/\/lodash.com\/docs#bindAll\">_.bindAll(object, methodNames)<\/a>\u3002<\/p>\n<h2>\u90e8\u5206\uff08\u5e94\u7528\uff09\u51fd\u6570\uff08Partial functions\uff09<\/h2>\n<p>\u5230\u73b0\u5728\u4e3a\u6b62\uff0c\u6211\u4eec\u53ea\u5728\u8c08\u8bba\u7ed1\u5b9a\u00a0<code>this<\/code>\u3002\u8ba9\u6211\u4eec\u518d\u6df1\u5165\u4e00\u6b65\u3002<br \/>\n\u6211\u4eec\u4e0d\u4ec5\u53ef\u4ee5\u7ed1\u5b9a\u00a0<code>this<\/code>\uff0c\u8fd8\u53ef\u4ee5\u7ed1\u5b9a\u53c2\u6570\uff08arguments\uff09\u3002\u867d\u7136\u5f88\u5c11\u8fd9\u4e48\u505a\uff0c\u4f46\u6709\u65f6\u5b83\u53ef\u4ee5\u6d3e\u4e0a\u7528\u573a\u3002<br \/>\n<code>bind<\/code>\u00a0\u7684\u5b8c\u6574\u8bed\u6cd5\u5982\u4e0b\uff1a<\/p>\n<pre><code class=\"language-js\">let bound = func.bind(context, [arg1], [arg2], ...);\n<\/code><\/pre>\n<p>\u5b83\u5141\u8bb8\u5c06\u4e0a\u4e0b\u6587\u7ed1\u5b9a\u4e3a\u00a0<code>this<\/code>\uff0c\u4ee5\u53ca\u7ed1\u5b9a\u51fd\u6570\u7684\u90e8\u5206\u53c2\u6570\u3002<br \/>\n\u4f8b\u5982\uff0c\u6211\u4eec\u6709\u4e00\u4e2a\u4e58\u6cd5\u51fd\u6570\u00a0<code>mul(a, b)<\/code>\uff1a<br \/>\n\u8ba9\u6211\u4eec\u4f7f\u7528\u00a0<code>bind<\/code>\u00a0\u5728\u8be5\u51fd\u6570\u57fa\u7840\u4e0a\u521b\u5efa\u4e00\u4e2a\u00a0<code>double<\/code>\u00a0\u51fd\u6570\uff1a<\/p>\n<pre><code class=\"language-js\">function mul(a, b) {\n  return a * b;\n}\n\nlet double = mul.bind(null, 2);\n\nalert( double(3) ); \/\/ = mul(2, 3) = 6\nalert( double(4) ); \/\/ = mul(2, 4) = 8\nalert( double(5) ); \/\/ = mul(2, 5) = 10\n<\/code><\/pre>\n<p>\u5bf9\u00a0<code>mul.bind(null, 2)<\/code>\u00a0\u7684\u8c03\u7528\u521b\u5efa\u4e86\u4e00\u4e2a\u65b0\u51fd\u6570\u00a0<code>double<\/code>\uff0c\u5b83\u5c06\u8c03\u7528\u4f20\u9012\u5230\u00a0<code>mul<\/code>\uff0c\u5c06\u00a0<code>null<\/code>\u00a0\u7ed1\u5b9a\u4e3a\u4e0a\u4e0b\u6587\uff0c\u5e76\u5c06\u00a0<code>2<\/code>\u00a0\u7ed1\u5b9a\u4e3a\u7b2c\u4e00\u4e2a\u53c2\u6570\u3002\u5e76\u4e14\uff0c\u53c2\u6570\uff08arguments\uff09\u5747\u88ab\u201c\u539f\u6837\u201d\u4f20\u9012\u3002<br \/>\n\u5b83\u88ab\u79f0\u4e3a\u00a0<a href=\"https:\/\/en.wikipedia.org\/wiki\/Partial_application\">\u51fd\u6570\u7684\u90e8\u5206\u5e94\u7528\uff08partial function application\uff09<\/a>\u00a0\u2014\u2014 \u6211\u4eec\u901a\u8fc7\u7ed1\u5b9a\u5148\u6709\u51fd\u6570\u7684\u4e00\u4e9b\u53c2\u6570\u6765\u521b\u5efa\u4e00\u4e2a\u65b0\u51fd\u6570\u3002<br \/>\n\u8bf7\u6ce8\u610f\uff0c\u8fd9\u91cc\u6211\u4eec\u5b9e\u9645\u4e0a\u6ca1\u6709\u7528\u5230\u00a0<code>this<\/code>\u3002\u4f46\u662f\u00a0<code>bind<\/code>\u00a0\u9700\u8981\u5b83\uff0c\u6240\u4ee5\u6211\u4eec\u5fc5\u987b\u4f20\u5165\u00a0<code>null<\/code>\u00a0\u4e4b\u7c7b\u7684\u4e1c\u897f\u3002<br \/>\n\u4e3a\u4ec0\u4e48\u6211\u4eec\u901a\u5e38\u4f1a\u521b\u5efa\u4e00\u4e2a\u90e8\u5206\u5e94\u7528\u51fd\u6570\uff1f<br \/>\n\u597d\u5904\u662f\u6211\u4eec\u53ef\u4ee5\u521b\u5efa\u4e00\u4e2a\u5177\u6709\u53ef\u8bfb\u6027\u9ad8\u7684\u540d\u5b57\uff08<code>double<\/code>\uff0c<code>triple<\/code>\uff09\u7684\u72ec\u7acb\u51fd\u6570\u3002\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u5b83\uff0c\u5e76\u4e14\u4e0d\u5fc5\u6bcf\u6b21\u90fd\u63d0\u4f9b\u4e00\u4e2a\u53c2\u6570\uff0c\u56e0\u4e3a\u53c2\u6570\u662f\u88ab\u7ed1\u5b9a\u4e86\u7684\u3002<br \/>\n\u53e6\u4e00\u65b9\u9762\uff0c\u5f53\u6211\u4eec\u6709\u4e00\u4e2a\u975e\u5e38\u7075\u6d3b\u7684\u51fd\u6570\uff0c\u5e76\u5e0c\u671b\u6709\u4e00\u4e2a\u4e0d\u90a3\u4e48\u7075\u6d3b\u7684\u53d8\u578b\u65f6\uff0c\u90e8\u5206\u5e94\u7528\u51fd\u6570\u4f1a\u975e\u5e38\u6709\u7528\u3002<br \/>\n\u4f8b\u5982\uff0c\u6211\u4eec\u6709\u4e00\u4e2a\u51fd\u6570\u00a0<code>send(from, to, text)<\/code>\u3002\u7136\u540e\uff0c\u5728\u4e00\u4e2a\u00a0<code>user<\/code>\u00a0\u5bf9\u8c61\u7684\u5185\u90e8\uff0c\u6211\u4eec\u53ef\u80fd\u5e0c\u671b\u5bf9\u5b83\u4f7f\u7528\u00a0<code>send<\/code>\u00a0\u7684\u90e8\u5206\u5e94\u7528\u51fd\u6570\u53d8\u578b\uff1a\u4ece\u5f53\u524d user \u53d1\u9001\u00a0<code>sendTo(to, text)<\/code>\u3002<\/p>\n<h2>\u5728\u6ca1\u6709\u4e0a\u4e0b\u6587\u60c5\u51b5\u4e0b\u7684partial<\/h2>\n<p>\u5f53\u6211\u4eec\u60f3\u7ed1\u5b9a\u4e00\u4e9b\u53c2\u6570\uff08arguments\uff09\uff0c\u4f46\u662f\u4e0d\u60f3\u7ed1\u5b9a\u4e0a\u4e0b\u6587\u00a0<code>this<\/code>\uff0c\u5e94\u8be5\u600e\u4e48\u529e\uff1f\u4f8b\u5982\uff0c\u5bf9\u4e8e\u4e00\u4e2a\u5bf9\u8c61\u65b9\u6cd5\u3002<br \/>\n\u539f\u751f\u7684\u00a0<code>bind<\/code>\u00a0\u4e0d\u5141\u8bb8\u8fd9\u79cd\u60c5\u51b5\u3002\u6211\u4eec\u4e0d\u53ef\u4ee5\u7701\u7565\u4e0a\u4e0b\u6587\u76f4\u63a5\u8df3\u5230\u53c2\u6570\uff08arguments\uff09\u3002<br \/>\n\u5e78\u8fd0\u7684\u662f\uff0c\u4ec5\u7ed1\u5b9a\u53c2\u6570\uff08arguments\uff09\u7684\u51fd\u6570\u00a0<code>partial<\/code>\u00a0\u6bd4\u8f83\u5bb9\u6613\u5b9e\u73b0\u3002<\/p>\n<pre><code class=\"language-js\">function partial(func, ...argsBound) {\n  return function(...args) { \/\/ (*)\n    return func.call(this, ...argsBound, ...args);\n  }\n}\n\n\/\/ \u7528\u6cd5\uff1a\nlet user = {\n  firstName: &quot;John&quot;,\n  say(time, phrase) {\n    alert(`[${time}] ${this.firstName}: ${phrase}!`);\n  }\n};\n\n\/\/ \u6dfb\u52a0\u4e00\u4e2a\u5e26\u6709\u7ed1\u5b9a\u65f6\u95f4\u7684 partial \u65b9\u6cd5\nuser.sayNow = partial(user.say, new Date().getHours() + ':' + new Date().getMinutes());\n\nuser.sayNow(&quot;Hello&quot;);\n\/\/ \u7c7b\u4f3c\u4e8e\u8fd9\u6837\u7684\u4e00\u4e9b\u5185\u5bb9\uff1a\n\/\/ [10:00] John: Hello!\n<\/code><\/pre>\n<p><code>partial(func[, arg1, arg2...])<\/code>\u00a0\u8c03\u7528\u7684\u7ed3\u679c\u662f\u4e00\u4e2a\u5305\u88c5\u5668\u00a0<code>(*)<\/code>\uff0c\u5b83\u8c03\u7528\u00a0<code>func<\/code>\u00a0\u5e76\u5177\u6709\u4ee5\u4e0b\u5185\u5bb9\uff1a<\/p>\n<ul>\n<li>\u4e0e\u5b83\u83b7\u5f97\u7684\u51fd\u6570\u5177\u6709\u76f8\u540c\u7684\u00a0<code>this<\/code>\uff08\u5bf9\u4e8e\u00a0<code>user.sayNow<\/code>\u00a0\u8c03\u7528\u6765\u8bf4\uff0c\u5b83\u662f\u00a0<code>user<\/code>\uff09<\/li>\n<li>\u7136\u540e\u7ed9\u5b83\u00a0<code>...argsBound<\/code>\u00a0\u2014\u2014 \u6765\u81ea\u4e8e\u00a0<code>partial<\/code>\u00a0\u8c03\u7528\u7684\u53c2\u6570\uff08<code>&quot;10:00&quot;<\/code>\uff09<\/li>\n<li>\u7136\u540e\u7ed9\u5b83\u00a0<code>...args<\/code>\u00a0\u2014\u2014 \u7ed9\u5305\u88c5\u5668\u7684\u53c2\u6570\uff08<code>&quot;Hello&quot;<\/code>\uff09<br \/>\n\u4f7f\u7528 spread \u53ef\u4ee5\u5f88\u5bb9\u6613\u5b9e\u73b0\u8fd9\u4e9b\u64cd\u4f5c\uff0c\u5bf9\u5427\uff1f<br \/>\n\u6b64\u5916\uff0c\u8fd8\u6709\u6765\u81ea lodash \u5e93\u7684\u73b0\u6210\u7684\u00a0<a href=\"https:\/\/lodash.com\/docs#partial\">_.partial<\/a>\u00a0\u5b9e\u73b0\u3002<\/li>\n<\/ul>\n<h1>\u6df1\u5165\u7406\u89e3\u7bad\u5934\u51fd\u6570<\/h1>\n<p>\u8ba9\u6211\u4eec\u6df1\u5165\u7814\u7a76\u4e00\u4e0b\u7bad\u5934\u51fd\u6570\u3002<br \/>\n\u7bad\u5934\u51fd\u6570\u4e0d\u4ec5\u4ec5\u662f\u7f16\u5199\u7b80\u6d01\u4ee3\u7801\u7684\u201c\u6377\u5f84\u201d\u3002\u5b83\u8fd8\u5177\u6709\u975e\u5e38\u7279\u6b8a\u4e14\u6709\u7528\u7684\u7279\u6027\u3002<br \/>\nJavaScript \u5145\u6ee1\u4e86\u6211\u4eec\u9700\u8981\u7f16\u5199\u5728\u5176\u4ed6\u5730\u65b9\u6267\u884c\u7684\u5c0f\u51fd\u6570\u7684\u60c5\u51b5\u3002<br \/>\n\u4f8b\u5982\uff1a<\/p>\n<ul>\n<li><code>arr.forEach(func)<\/code>\u00a0\u2014\u2014\u00a0<code>forEach<\/code>\u00a0\u5bf9\u6bcf\u4e2a\u6570\u7ec4\u5143\u7d20\u90fd\u6267\u884c\u00a0<code>func<\/code>\u3002<\/li>\n<li><code>setTimeout(func)<\/code>\u00a0\u2014\u2014\u00a0<code>func<\/code>\u00a0\u7531\u5185\u5efa\u8c03\u5ea6\u5668\u6267\u884c\u3002<\/li>\n<li>\u2026\u2026\u8fd8\u6709\u66f4\u591a\u3002<br \/>\nJavaScript \u7684\u7cbe\u9ad3\u5728\u4e8e\u521b\u5efa\u4e00\u4e2a\u51fd\u6570\u5e76\u5c06\u5176\u4f20\u9012\u5230\u67d0\u4e2a\u5730\u65b9\u3002<br \/>\n\u5728\u8fd9\u6837\u7684\u51fd\u6570\u4e2d\uff0c\u6211\u4eec\u901a\u5e38\u4e0d\u60f3\u79bb\u5f00\u5f53\u524d\u4e0a\u4e0b\u6587\u3002\u8fd9\u5c31\u662f\u7bad\u5934\u51fd\u6570\u7684\u4e3b\u6218\u573a\u5566\u3002<\/li>\n<\/ul>\n<h2>\u7bad\u5934\u51fd\u6570\u6ca1\u6709 this<\/h2>\n<p>\u6b63\u5982\u6211\u4eec\u5728\u00a0<a href=\"https:\/\/zh.javascript.info\/object-methods\">\u5bf9\u8c61\u65b9\u6cd5\uff0c&quot;this&quot;<\/a>\u00a0\u4e00\u7ae0\u4e2d\u6240\u5b66\u5230\u7684\uff0c\u7bad\u5934\u51fd\u6570\u6ca1\u6709\u00a0<code>this<\/code>\u3002\u5982\u679c\u8bbf\u95ee\u00a0<code>this<\/code>\uff0c\u5219\u4f1a\u4ece\u5916\u90e8\u83b7\u53d6\u3002<\/p>\n<blockquote>\n<p>\u4e0d\u80fd\u5bf9\u7bad\u5934\u51fd\u6570\u8fdb\u884c\u00a0<code>new<\/code>\u00a0\u64cd\u4f5c<br \/>\n\u4e0d\u5177\u6709\u00a0<code>this<\/code>\u00a0\u81ea\u7136\u4e5f\u5c31\u610f\u5473\u7740\u53e6\u4e00\u4e2a\u9650\u5236\uff1a\u7bad\u5934\u51fd\u6570\u4e0d\u80fd\u7528\u4f5c\u6784\u9020\u5668\uff08constructor\uff09\u3002\u4e0d\u80fd\u7528\u00a0<code>new<\/code>\u00a0\u8c03\u7528\u5b83\u4eec\u3002<\/p>\n<\/blockquote>\n<blockquote>\n<p>\u7bad\u5934\u51fd\u6570 VS bind<br \/>\n\u7bad\u5934\u51fd\u6570\u00a0<code>=&gt;<\/code>\u00a0\u548c\u4f7f\u7528\u00a0<code>.bind(this)<\/code>\u00a0\u8c03\u7528\u7684\u5e38\u89c4\u51fd\u6570\u4e4b\u95f4\u6709\u7ec6\u5fae\u7684\u5dee\u522b\uff1a<\/p>\n<ul>\n<li><code>.bind(this)<\/code>\u00a0\u521b\u5efa\u4e86\u4e00\u4e2a\u8be5\u51fd\u6570\u7684\u201c\u7ed1\u5b9a\u7248\u672c\u201d\u3002<\/li>\n<li>\u7bad\u5934\u51fd\u6570\u00a0<code>=&gt;<\/code>\u00a0\u6ca1\u6709\u521b\u5efa\u4efb\u4f55\u7ed1\u5b9a\u3002\u7bad\u5934\u51fd\u6570\u53ea\u662f\u6ca1\u6709\u00a0<code>this<\/code>\u3002<code>this<\/code>\u00a0\u7684\u67e5\u627e\u4e0e\u5e38\u89c4\u53d8\u91cf\u7684\u641c\u7d22\u65b9\u5f0f\u5b8c\u5168\u76f8\u540c\uff1a\u5728\u5916\u90e8\u8bcd\u6cd5\u73af\u5883\u4e2d\u67e5\u627e\u3002<\/li>\n<\/ul>\n<\/blockquote>\n<h2>\u7bad\u5934\u51fd\u6570\u6ca1\u6709 arguments<\/h2>\n<p>\u7bad\u5934\u51fd\u6570\u4e5f\u6ca1\u6709\u00a0<code>arguments<\/code>\u00a0\u53d8\u91cf\u3002<br 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