{"id":680,"date":"2024-06-25T23:40:01","date_gmt":"2024-06-25T15:40:01","guid":{"rendered":"https:\/\/levin.ink\/?p=680"},"modified":"2024-06-25T23:40:01","modified_gmt":"2024-06-25T15:40:01","slug":"js-3-14-%e5%8a%a0%e8%bd%bd%e6%96%87%e6%a1%a3%e5%92%8c%e5%85%b6%e4%bb%96%e8%b5%84%e6%ba%90","status":"publish","type":"post","link":"https:\/\/levin.ink\/?p=680","title":{"rendered":"JS &#8211; 3-14 \u52a0\u8f7d\u6587\u6863\u548c\u5176\u4ed6\u8d44\u6e90"},"content":{"rendered":"<h1>\u9875\u9762\u751f\u547d\u5468\u671f DOMContentLoaded load beforeunload unload<\/h1>\n<p>HTML \u9875\u9762\u7684\u751f\u547d\u5468\u671f\u5305\u542b\u4e09\u4e2a\u91cd\u8981\u4e8b\u4ef6\uff1a<\/p>\n<ul>\n<li><code>DOMContentLoaded<\/code>\u00a0\u2014\u2014 \u6d4f\u89c8\u5668\u5df2\u5b8c\u5168\u52a0\u8f7d HTML\uff0c\u5e76\u6784\u5efa\u4e86 DOM \u6811\uff0c\u4f46\u50cf\u00a0<code>&lt;img&gt;<\/code>\u00a0\u548c\u6837\u5f0f\u8868\u4e4b\u7c7b\u7684\u5916\u90e8\u8d44\u6e90\u53ef\u80fd\u5c1a\u672a\u52a0\u8f7d\u5b8c\u6210\u3002<\/li>\n<li><code>load<\/code>\u00a0\u2014\u2014 \u6d4f\u89c8\u5668\u4e0d\u4ec5\u52a0\u8f7d\u5b8c\u6210\u4e86 HTML\uff0c\u8fd8\u52a0\u8f7d\u5b8c\u6210\u4e86\u6240\u6709\u5916\u90e8\u8d44\u6e90\uff1a\u56fe\u7247\uff0c\u6837\u5f0f\u7b49\u3002<\/li>\n<li><code>beforeunload\/unload<\/code>\u00a0\u2014\u2014 \u5f53\u7528\u6237\u6b63\u5728\u79bb\u5f00\u9875\u9762\u65f6\u3002<br \/>\n\u6bcf\u4e2a\u4e8b\u4ef6\u90fd\u662f\u6709\u7528\u7684\uff1a<\/li>\n<li><code>DOMContentLoaded<\/code>\u00a0\u4e8b\u4ef6 \u2014\u2014 DOM \u5df2\u7ecf\u5c31\u7eea\uff0c\u56e0\u6b64\u5904\u7406\u7a0b\u5e8f\u53ef\u4ee5\u67e5\u627e DOM \u8282\u70b9\uff0c\u5e76\u521d\u59cb\u5316\u63a5\u53e3\u3002<\/li>\n<li><code>load<\/code>\u00a0\u4e8b\u4ef6 \u2014\u2014 \u5916\u90e8\u8d44\u6e90\u5df2\u52a0\u8f7d\u5b8c\u6210\uff0c\u6837\u5f0f\u5df2\u88ab\u5e94\u7528\uff0c\u56fe\u7247\u5927\u5c0f\u4e5f\u5df2\u77e5\u4e86\u3002<\/li>\n<li><code>beforeunload<\/code>\u00a0\u4e8b\u4ef6 \u2014\u2014 \u7528\u6237\u6b63\u5728\u79bb\u5f00\uff1a\u6211\u4eec\u53ef\u4ee5\u68c0\u67e5\u7528\u6237\u662f\u5426\u4fdd\u5b58\u4e86\u66f4\u6539\uff0c\u5e76\u8be2\u95ee\u4ed6\u662f\u5426\u771f\u7684\u8981\u79bb\u5f00\u3002<\/li>\n<li><code>unload<\/code>\u00a0\u4e8b\u4ef6 \u2014\u2014 \u7528\u6237\u51e0\u4e4e\u5df2\u7ecf\u79bb\u5f00\u4e86\uff0c\u4f46\u662f\u6211\u4eec\u4ecd\u7136\u53ef\u4ee5\u542f\u52a8\u4e00\u4e9b\u64cd\u4f5c\uff0c\u4f8b\u5982\u53d1\u9001\u7edf\u8ba1\u6570\u636e\u3002<br \/>\n\u6211\u4eec\u63a2\u7d22\u4e00\u4e0b\u8fd9\u4e9b\u4e8b\u4ef6\u7684\u7ec6\u8282\u3002<\/li>\n<\/ul>\n<h2>DOMContentLoaded<\/h2>\n<p><code>DOMContentLoaded<\/code>\u00a0\u4e8b\u4ef6\u53d1\u751f\u5728\u00a0<code>document<\/code>\u00a0\u5bf9\u8c61\u4e0a\u3002<br \/>\n\u6211\u4eec\u5fc5\u987b\u4f7f\u7528\u00a0<code>addEventListener<\/code>\u00a0\u6765\u6355\u83b7\u5b83\uff1a<\/p>\n<pre><code class=\"language-js\">document.addEventListener(&quot;DOMContentLoaded&quot;, ready);\n\/\/ \u4e0d\u662f &quot;document.onDOMContentLoaded = ...&quot;\n<\/code><\/pre>\n<p>\u4f8b\u5982\uff1a<\/p>\n<pre><code class=\"language-html\">&lt;script&gt;\n  function ready() {\n    alert('DOM is ready');\n\n    \/\/ \u56fe\u7247\u76ee\u524d\u5c1a\u672a\u52a0\u8f7d\u5b8c\u6210\uff08\u9664\u975e\u5df2\u7ecf\u88ab\u7f13\u5b58\uff09\uff0c\u6240\u4ee5\u56fe\u7247\u7684\u5927\u5c0f\u4e3a 0x0\n    alert(`Image size: ${img.offsetWidth}x${img.offsetHeight}`);\n  }\n\n  document.addEventListener(&quot;DOMContentLoaded&quot;, ready);\n&lt;\/script&gt;\n\n&lt;img id=&quot;img&quot; src=&quot;https:\/\/en.js.cx\/clipart\/train.gif?speed=1&amp;cache=0&quot;&gt;\n<\/code><\/pre>\n<p>\u5728\u793a\u4f8b\u4e2d\uff0c<code>DOMContentLoaded<\/code>\u00a0\u5904\u7406\u7a0b\u5e8f\u5728\u6587\u6863\u52a0\u8f7d\u5b8c\u6210\u540e\u89e6\u53d1\uff0c\u6240\u4ee5\u5b83\u53ef\u4ee5\u67e5\u770b\u6240\u6709\u5143\u7d20\uff0c\u5305\u62ec\u5b83\u4e0b\u9762\u7684\u00a0<code>&lt;img&gt;<\/code>\u00a0\u5143\u7d20\u3002<br \/>\n\u4f46\u662f\uff0c\u5b83\u4e0d\u4f1a\u7b49\u5f85\u56fe\u7247\u52a0\u8f7d\u3002\u56e0\u6b64\uff0c<code>alert<\/code>\u00a0\u663e\u793a\u5176\u5927\u5c0f\u4e3a\u96f6\u3002<br \/>\n\u4e4d\u4e00\u770b\uff0c<code>DOMContentLoaded<\/code>\u00a0\u4e8b\u4ef6\u975e\u5e38\u7b80\u5355\u3002DOM \u6811\u51c6\u5907\u5c31\u7eea \u2014\u2014 \u8fd9\u662f\u5b83\u7684\u89e6\u53d1\u6761\u4ef6\u3002\u5b83\u5e76\u6ca1\u6709\u4ec0\u4e48\u7279\u522b\u4e4b\u5904\u3002<\/p>\n<h3>DOMContentLoaded \u548c\u811a\u672c<\/h3>\n<p>\u5f53\u6d4f\u89c8\u5668\u5904\u7406\u4e00\u4e2a HTML \u6587\u6863\uff0c\u5e76\u5728\u6587\u6863\u4e2d\u9047\u5230\u00a0<code>&lt;script&gt;<\/code>\u00a0\u6807\u7b7e\u65f6\uff0c\u5c31\u4f1a\u5728\u7ee7\u7eed\u6784\u5efa DOM \u4e4b\u524d\u8fd0\u884c\u5b83\u3002\u8fd9\u662f\u4e00\u79cd\u9632\u8303\u63aa\u65bd\uff0c\u56e0\u4e3a\u811a\u672c\u53ef\u80fd\u60f3\u8981\u4fee\u6539 DOM\uff0c\u751a\u81f3\u5bf9\u5176\u6267\u884c\u00a0<code>document.write<\/code>\u00a0\u64cd\u4f5c\uff0c\u6240\u4ee5\u00a0<code>DOMContentLoaded<\/code>\u00a0\u5fc5\u987b\u7b49\u5f85\u811a\u672c\u6267\u884c\u7ed3\u675f\u3002<br \/>\n\u56e0\u6b64\uff0c<code>DOMContentLoaded<\/code>\u00a0\u80af\u5b9a\u5728\u4e0b\u9762\u7684\u8fd9\u4e9b\u811a\u672c\u6267\u884c\u7ed3\u675f\u4e4b\u540e\u53d1\u751f\uff1a<\/p>\n<pre><code class=\"language-html\">&lt;script&gt;\n  document.addEventListener(&quot;DOMContentLoaded&quot;, () =&gt; {\n    alert(&quot;DOM ready!&quot;);\n  });\n&lt;\/script&gt;\n\n&lt;script src=&quot;https:\/\/cdnjs.cloudflare.com\/ajax\/libs\/lodash.js\/4.3.0\/lodash.js&quot;&gt;&lt;\/script&gt;\n\n&lt;script&gt;\n  alert(&quot;Library loaded, inline script executed&quot;);\n&lt;\/script&gt;\n<\/code><\/pre>\n<p>\u5728\u4e0a\u9762\u8fd9\u4e2a\u4f8b\u5b50\u4e2d\uff0c\u6211\u4eec\u9996\u5148\u4f1a\u770b\u5230 \u201cLibrary loaded\u2026\u201d\uff0c\u7136\u540e\u624d\u4f1a\u770b\u5230 \u201cDOM ready!\u201d\uff08\u6240\u6709\u811a\u672c\u90fd\u5df2\u7ecf\u6267\u884c\u7ed3\u675f\uff09\u3002<\/p>\n<blockquote>\n<p>\u4e0d\u4f1a\u963b\u585e\u00a0<code>DOMContentLoaded<\/code>\u00a0\u7684\u811a\u672c<br \/>\n\u6b64\u89c4\u5219\u6709\u4e24\u4e2a\u4f8b\u5916\uff1a<\/p>\n<ol>\n<li>\u5177\u6709\u00a0<code>async<\/code>\u00a0\u7279\u6027\uff08attribute\uff09\u7684\u811a\u672c\u4e0d\u4f1a\u963b\u585e\u00a0<code>DOMContentLoaded<\/code>\uff0c<a href=\"https:\/\/zh.javascript.info\/script-async-defer\">\u7a0d\u540e<\/a>\u00a0\u6211\u4eec\u4f1a\u8bb2\u5230\u3002<\/li>\n<li>\u4f7f\u7528\u00a0<code>document.createElement('script')<\/code>\u00a0\u52a8\u6001\u751f\u6210\u5e76\u6dfb\u52a0\u5230\u7f51\u9875\u7684\u811a\u672c\u4e5f\u4e0d\u4f1a\u963b\u585e\u00a0<code>DOMContentLoaded<\/code>\u3002<\/li>\n<\/ol>\n<\/blockquote>\n<h3>DOMContentLoaded \u548c\u6837\u5f0f<\/h3>\n<p>\u5916\u90e8\u6837\u5f0f\u8868\u4e0d\u4f1a\u5f71\u54cd DOM\uff0c\u56e0\u6b64\u00a0<code>DOMContentLoaded<\/code>\u00a0\u4e0d\u4f1a\u7b49\u5f85\u5b83\u4eec\u3002<br \/>\n\u4f46\u8fd9\u91cc\u6709\u4e00\u4e2a\u9677\u9631\u3002\u5982\u679c\u5728\u6837\u5f0f\u540e\u9762\u6709\u4e00\u4e2a\u811a\u672c\uff0c\u90a3\u4e48\u8be5\u811a\u672c\u5fc5\u987b\u7b49\u5f85\u6837\u5f0f\u8868\u52a0\u8f7d\u5b8c\u6210\uff1a<\/p>\n<pre><code class=\"language-html\">&lt;link type=&quot;text\/css&quot; rel=&quot;stylesheet&quot; href=&quot;style.css&quot;&gt;\n&lt;script&gt;\n  \/\/ \u5728\u6837\u5f0f\u8868\u52a0\u8f7d\u5b8c\u6210\u4e4b\u524d\uff0c\u811a\u672c\u90fd\u4e0d\u4f1a\u6267\u884c\n  alert(getComputedStyle(document.body).marginTop);\n&lt;\/script&gt;\n<\/code><\/pre>\n<p>\u539f\u56e0\u662f\uff0c\u811a\u672c\u53ef\u80fd\u60f3\u8981\u83b7\u53d6\u5143\u7d20\u7684\u5750\u6807\u548c\u5176\u4ed6\u4e0e\u6837\u5f0f\u76f8\u5173\u7684\u5c5e\u6027\uff0c\u5982\u4e0a\u4f8b\u6240\u793a\u3002\u56e0\u6b64\uff0c\u5b83\u5fc5\u987b\u7b49\u5f85\u6837\u5f0f\u52a0\u8f7d\u5b8c\u6210\u3002<br \/>\n\u5f53\u00a0<code>DOMContentLoaded<\/code>\u00a0\u7b49\u5f85\u811a\u672c\u65f6\uff0c\u5b83\u73b0\u5728\u4e5f\u5728\u7b49\u5f85\u811a\u672c\u524d\u9762\u7684\u6837\u5f0f\u3002<\/p>\n<h3>\u6d4f\u89c8\u5668\u5185\u5efa\u7684\u81ea\u52a8\u586b\u5145<\/h3>\n<p>Firefox\uff0cChrome \u548c Opera \u90fd\u4f1a\u5728\u00a0<code>DOMContentLoaded<\/code>\u00a0\u4e2d\u81ea\u52a8\u586b\u5145\u8868\u5355\u3002<br \/>\n\u4f8b\u5982\uff0c\u5982\u679c\u9875\u9762\u6709\u4e00\u4e2a\u5e26\u6709\u767b\u5f55\u540d\u548c\u5bc6\u7801\u7684\u8868\u5355\uff0c\u5e76\u4e14\u6d4f\u89c8\u5668\u8bb0\u4f4f\u4e86\u8fd9\u4e9b\u503c\uff0c\u90a3\u4e48\u5728\u00a0<code>DOMContentLoaded<\/code>\u00a0\u4e0a\uff0c\u6d4f\u89c8\u5668\u4f1a\u5c1d\u8bd5\u81ea\u52a8\u586b\u5145\u5b83\u4eec\uff08\u5982\u679c\u5f97\u5230\u4e86\u7528\u6237\u5141\u8bb8\uff09\u3002<br \/>\n\u56e0\u6b64\uff0c\u5982\u679c\u00a0<code>DOMContentLoaded<\/code>\u00a0\u88ab\u9700\u8981\u52a0\u8f7d\u5f88\u957f\u65f6\u95f4\u7684\u811a\u672c\u5ef6\u8fdf\u89e6\u53d1\uff0c\u90a3\u4e48\u81ea\u52a8\u586b\u5145\u4e5f\u4f1a\u7b49\u5f85\u3002\u4f60\u53ef\u80fd\u5728\u67d0\u4e9b\u7f51\u7ad9\u4e0a\u770b\u5230\u8fc7\uff08\u5982\u679c\u4f60\u4f7f\u7528\u6d4f\u89c8\u5668\u81ea\u52a8\u586b\u5145\uff09\u2014\u2014 \u767b\u5f55\u540d\/\u5bc6\u7801\u5b57\u6bb5\u4e0d\u4f1a\u7acb\u5373\u81ea\u52a8\u586b\u5145\uff0c\u800c\u662f\u5728\u9875\u9762\u88ab\u5b8c\u5168\u52a0\u8f7d\u524d\u4f1a\u5ef6\u8fdf\u586b\u5145\u3002\u8fd9\u5b9e\u9645\u4e0a\u662f\u00a0<code>DOMContentLoaded<\/code>\u00a0\u4e8b\u4ef6\u4e4b\u524d\u7684\u5ef6\u8fdf\u3002<\/p>\n<h2>window.onunload<\/h2>\n<p>\u5f53\u8bbf\u95ee\u8005\u79bb\u5f00\u9875\u9762\u65f6\uff0c<code>window<\/code>\u00a0\u5bf9\u8c61\u4e0a\u7684\u00a0<code>unload<\/code>\u00a0\u4e8b\u4ef6\u5c31\u4f1a\u88ab\u89e6\u53d1\u3002\u6211\u4eec\u53ef\u4ee5\u5728\u90a3\u91cc\u505a\u4e00\u4e9b\u4e0d\u6d89\u53ca\u5ef6\u8fdf\u7684\u64cd\u4f5c\uff0c\u4f8b\u5982\u5173\u95ed\u76f8\u5173\u7684\u5f39\u51fa\u7a97\u53e3\u3002<br \/>\n\u6709\u4e00\u4e2a\u503c\u5f97\u6ce8\u610f\u7684\u7279\u6b8a\u60c5\u51b5\u662f\u53d1\u9001\u5206\u6790\u6570\u636e\u3002<br \/>\n\u5047\u8bbe\u6211\u4eec\u6536\u96c6\u6709\u5173\u9875\u9762\u4f7f\u7528\u60c5\u51b5\u7684\u6570\u636e\uff1a\u9f20\u6807\u70b9\u51fb\uff0c\u6eda\u52a8\uff0c\u88ab\u67e5\u770b\u7684\u9875\u9762\u533a\u57df\u7b49\u3002<br \/>\n\u81ea\u7136\u5730\uff0c\u5f53\u7528\u6237\u8981\u79bb\u5f00\u7684\u65f6\u5019\uff0c\u6211\u4eec\u5e0c\u671b\u901a\u8fc7\u00a0<code>unload<\/code>\u00a0\u4e8b\u4ef6\u5c06\u6570\u636e\u4fdd\u5b58\u5230\u6211\u4eec\u7684\u670d\u52a1\u5668\u4e0a\u3002<br \/>\n\u6709\u4e00\u4e2a\u7279\u6b8a\u7684\u00a0<code>navigator.sendBeacon(url, data)<\/code>\u00a0\u65b9\u6cd5\u53ef\u4ee5\u6ee1\u8db3\u8fd9\u79cd\u9700\u6c42\uff0c\u8be6\u89c1\u89c4\u8303\u00a0<a href=\"https:\/\/w3c.github.io\/beacon\/\">https:\/\/w3c.github.io\/beacon\/<\/a>\u3002<br \/>\n\u5b83\u5728\u540e\u53f0\u53d1\u9001\u6570\u636e\uff0c\u8f6c\u6362\u5230\u53e6\u5916\u4e00\u4e2a\u9875\u9762\u4e0d\u4f1a\u6709\u5ef6\u8fdf\uff1a\u6d4f\u89c8\u5668\u79bb\u5f00\u9875\u9762\uff0c\u4f46\u4ecd\u7136\u5728\u6267\u884c\u00a0<code>sendBeacon<\/code>\u3002<br \/>\n\u4f7f\u7528\u65b9\u5f0f\u5982\u4e0b\uff1a<\/p>\n<pre><code class=\"language-js\">let analyticsData = { \/* \u5e26\u6709\u6536\u96c6\u7684\u6570\u636e\u7684\u5bf9\u8c61 *\/ };\n\nwindow.addEventListener(&quot;unload&quot;, function() {\n  navigator.sendBeacon(&quot;\/analytics&quot;, JSON.stringify(analyticsData));\n});\n<\/code><\/pre>\n<ul>\n<li>\u8bf7\u6c42\u4ee5 POST \u65b9\u5f0f\u53d1\u9001\u3002<\/li>\n<li>\u6211\u4eec\u4e0d\u4ec5\u80fd\u53d1\u9001\u5b57\u7b26\u4e32\uff0c\u8fd8\u80fd\u53d1\u9001\u8868\u5355\u4ee5\u53ca\u5176\u4ed6\u683c\u5f0f\u7684\u6570\u636e\uff0c\u5728\u00a0<a href=\"https:\/\/zh.javascript.info\/fetch\">Fetch<\/a>\u00a0\u4e00\u7ae0\u6709\u8be6\u7ec6\u8bb2\u89e3\uff0c\u4f46\u901a\u5e38\u5b83\u662f\u4e00\u4e2a\u5b57\u7b26\u4e32\u5316\u7684\u5bf9\u8c61\u3002<\/li>\n<li>\u6570\u636e\u5927\u5c0f\u9650\u5236\u5728 64kb\u3002<br \/>\n\u5f53\u00a0<code>sendBeacon<\/code>\u00a0\u8bf7\u6c42\u5b8c\u6210\u65f6\uff0c\u6d4f\u89c8\u5668\u53ef\u80fd\u5df2\u7ecf\u79bb\u5f00\u4e86\u6587\u6863\uff0c\u6240\u4ee5\u5c31\u65e0\u6cd5\u83b7\u53d6\u670d\u52a1\u5668\u54cd\u5e94\uff08\u5bf9\u4e8e\u5206\u6790\u6570\u636e\u6765\u8bf4\u901a\u5e38\u4e3a\u7a7a\uff09\u3002<br \/>\n\u8fd8\u6709\u4e00\u4e2a\u00a0<code>keep-alive<\/code>\u00a0\u6807\u5fd7\uff0c\u8be5\u6807\u5fd7\u7528\u4e8e\u5728\u00a0<a href=\"https:\/\/zh.javascript.info\/fetch\">fetch<\/a>\u00a0\u65b9\u6cd5\u4e2d\u4e3a\u901a\u7528\u7684\u7f51\u7edc\u8bf7\u6c42\u6267\u884c\u6b64\u7c7b\u201c\u79bb\u5f00\u9875\u9762\u540e\u201d\u7684\u8bf7\u6c42\u3002\u4f60\u53ef\u4ee5\u5728\u00a0<a href=\"https:\/\/zh.javascript.info\/fetch-api\">Fetch API<\/a>\u00a0\u4e00\u7ae0\u4e2d\u627e\u5230\u66f4\u591a\u76f8\u5173\u4fe1\u606f\u3002<br \/>\n\u5982\u679c\u6211\u4eec\u8981\u53d6\u6d88\u8df3\u8f6c\u5230\u53e6\u4e00\u9875\u9762\u7684\u64cd\u4f5c\uff0c\u5728\u8fd9\u91cc\u505a\u4e0d\u5230\u3002\u4f46\u662f\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u53e6\u4e00\u4e2a\u4e8b\u4ef6 \u2014\u2014\u00a0<code>onbeforeunload<\/code>\u3002<\/li>\n<\/ul>\n<h2>window.onbeforeunload<\/h2>\n<p>\u5982\u679c\u8bbf\u95ee\u8005\u89e6\u53d1\u4e86\u79bb\u5f00\u9875\u9762\u7684\u5bfc\u822a\uff08navigation\uff09\u6216\u8bd5\u56fe\u5173\u95ed\u7a97\u53e3\uff0c<code>beforeunload<\/code>\u00a0\u5904\u7406\u7a0b\u5e8f\u5c06\u8981\u6c42\u8fdb\u884c\u66f4\u591a\u786e\u8ba4\u3002<br \/>\n\u5982\u679c\u6211\u4eec\u8981\u53d6\u6d88\u4e8b\u4ef6\uff0c\u6d4f\u89c8\u5668\u4f1a\u8be2\u95ee\u7528\u6237\u662f\u5426\u786e\u5b9a\u3002<br \/>\n\u4f60\u53ef\u4ee5\u901a\u8fc7\u8fd0\u884c\u4e0b\u9762\u8fd9\u6bb5\u4ee3\u7801\uff0c\u7136\u540e\u91cd\u65b0\u52a0\u8f7d\u9875\u9762\u6765\u8fdb\u884c\u5c1d\u8bd5\uff1a<\/p>\n<pre><code class=\"language-js\">window.onbeforeunload = function() {\n  return false;\n};\n<\/code><\/pre>\n<p>\u7531\u4e8e\u5386\u53f2\u539f\u56e0\uff0c\u8fd4\u56de\u975e\u7a7a\u5b57\u7b26\u4e32\u4e5f\u88ab\u89c6\u4e3a\u53d6\u6d88\u4e8b\u4ef6\u3002\u5728\u4ee5\u524d\uff0c\u6d4f\u89c8\u5668\u66fe\u7ecf\u5c06\u5176\u663e\u793a\u4e3a\u6d88\u606f\uff0c\u4f46\u662f\u6839\u636e\u00a0<a href=\"https:\/\/html.spec.whatwg.org\/#unloading-documents\">\u73b0\u4ee3\u89c4\u8303<\/a>\u00a0\u6240\u8ff0\uff0c\u5b83\u4eec\u4e0d\u5e94\u8be5\u8fd9\u6837\u3002<br \/>\n\u8fd9\u91cc\u6709\u4e2a\u4f8b\u5b50\uff1a<\/p>\n<pre><code class=\"language-js\">window.onbeforeunload = function() {\n  return &quot;\u6709\u672a\u4fdd\u5b58\u7684\u503c\u3002\u786e\u8ba4\u8981\u79bb\u5f00\u5417\uff1f&quot;;\n};\n<\/code><\/pre>\n<p>\u5b83\u7684\u884c\u4e3a\u5df2\u7ecf\u6539\u53d8\u4e86\uff0c\u56e0\u4e3a\u6709\u4e9b\u7ad9\u957f\u901a\u8fc7\u663e\u793a\u8bef\u5bfc\u6027\u548c\u6076\u610f\u4fe1\u606f\u6ee5\u7528\u4e86\u6b64\u4e8b\u4ef6\u5904\u7406\u7a0b\u5e8f\u3002\u6240\u4ee5\uff0c\u76ee\u524d\u4e00\u4e9b\u65e7\u7684\u6d4f\u89c8\u5668\u53ef\u80fd\u4ecd\u5c06\u5176\u663e\u793a\u4e3a\u6d88\u606f\uff0c\u4f46\u9664\u6b64\u4e4b\u5916 \u2014\u2014 \u65e0\u6cd5\u81ea\u5b9a\u4e49\u663e\u793a\u7ed9\u7528\u6237\u7684\u6d88\u606f\u3002<\/p>\n<blockquote>\n<p><code>event.preventDefault()<\/code>\u00a0\u5728\u00a0<code>beforeunload<\/code>\u00a0\u5904\u7406\u7a0b\u5e8f\u4e2d\u4e0d\u8d77\u4f5c\u7528<br \/>\n\u8fd9\u542c\u8d77\u6765\u53ef\u80fd\u5f88\u5947\u602a\uff0c\u4f46\u5927\u591a\u6570\u6d4f\u89c8\u5668\u90fd\u4f1a\u5ffd\u7565\u00a0<code>event.preventDefault()<\/code>\u3002<br \/>\n\u8fd9\u610f\u5473\u7740\uff0c\u4ee5\u4e0b\u4ee3\u7801\u53ef\u80fd\u4e0d\u8d77\u4f5c\u7528\uff1a<\/p>\n<\/blockquote>\n<pre><code class=\"language-js\">window.addEventListener(&quot;beforeunload&quot;, (event) =&gt; {\n  \/\/ \u4e0d\u8d77\u4f5c\u7528\uff0c\u6240\u4ee5\u8fd9\u4e2a\u4e8b\u4ef6\u5904\u7406\u7a0b\u5e8f\u6ca1\u505a\u4efb\u4f55\u4e8b\u513f\n  event.preventDefault();\n});\n<\/code><\/pre>\n<blockquote>\n<p>\u76f8\u53cd\uff0c\u5728\u8fd9\u6837\u7684\u5904\u7406\u7a0b\u5e8f\u4e2d\uff0c\u5e94\u8be5\u5c06\u00a0<code>event.returnValue<\/code>\u00a0\u8bbe\u7f6e\u4e3a\u4e00\u4e2a\u5b57\u7b26\u4e32\uff0c\u4ee5\u83b7\u5f97\u7c7b\u4f3c\u4e8e\u4e0a\u9762\u4ee3\u7801\u7684\u7ed3\u679c\uff1a<\/p>\n<\/blockquote>\n<pre><code class=\"language-js\">window.addEventListener(&quot;beforeunload&quot;, (event) =&gt; {\n  \/\/ \u8d77\u4f5c\u7528\uff0c\u4e0e\u5728 window.onbeforeunload \u4e2d return \u503c\u7684\u6548\u679c\u662f\u4e00\u6837\u7684\n  event.returnValue = &quot;\u6709\u672a\u4fdd\u5b58\u7684\u503c\u3002\u786e\u8ba4\u8981\u79bb\u5f00\u5417\uff1f&quot;;\n});\n<\/code><\/pre>\n<h2>readyState<\/h2>\n<p>\u5982\u679c\u6211\u4eec\u5728\u6587\u6863\u52a0\u8f7d\u5b8c\u6210\u4e4b\u540e\u8bbe\u7f6e\u00a0<code>DOMContentLoaded<\/code>\u00a0\u4e8b\u4ef6\u5904\u7406\u7a0b\u5e8f\uff0c\u4f1a\u53d1\u751f\u4ec0\u4e48\uff1f<br \/>\n\u5f88\u81ea\u7136\u5730\uff0c\u5b83\u6c38\u8fdc\u4e0d\u4f1a\u8fd0\u884c\u3002<br \/>\n\u5728\u67d0\u4e9b\u60c5\u51b5\u4e0b\uff0c\u6211\u4eec\u4e0d\u786e\u5b9a\u6587\u6863\u662f\u5426\u5df2\u7ecf\u51c6\u5907\u5c31\u7eea\u3002\u6211\u4eec\u5e0c\u671b\u6211\u4eec\u7684\u51fd\u6570\u5728 DOM \u52a0\u8f7d\u5b8c\u6210\u65f6\u6267\u884c\uff0c\u65e0\u8bba\u73b0\u5728\u8fd8\u662f\u4ee5\u540e\u3002<br \/>\n<code>document.readyState<\/code>\u00a0\u5c5e\u6027\u53ef\u4ee5\u4e3a\u6211\u4eec\u63d0\u4f9b\u5f53\u524d\u52a0\u8f7d\u72b6\u6001\u7684\u4fe1\u606f\u3002<br \/>\n\u5b83\u6709 3 \u4e2a\u53ef\u80fd\u503c\uff1a<\/p>\n<ul>\n<li><code>loading<\/code>\u00a0\u2014\u2014 \u6587\u6863\u6b63\u5728\u88ab\u52a0\u8f7d\u3002<\/li>\n<li><code>interactive<\/code>\u00a0\u2014\u2014 \u6587\u6863\u88ab\u5168\u90e8\u8bfb\u53d6\u3002<\/li>\n<li><code>complete<\/code>\u00a0\u2014\u2014 \u6587\u6863\u88ab\u5168\u90e8\u8bfb\u53d6\uff0c\u5e76\u4e14\u6240\u6709\u8d44\u6e90\uff08\u4f8b\u5982\u56fe\u7247\u7b49\uff09\u90fd\u5df2\u52a0\u8f7d\u5b8c\u6210\u3002<br \/>\n\u6240\u4ee5\uff0c\u6211\u4eec\u53ef\u4ee5\u68c0\u67e5\u00a0<code>document.readyState<\/code>\u00a0\u5e76\u8bbe\u7f6e\u4e00\u4e2a\u5904\u7406\u7a0b\u5e8f\uff0c\u6216\u5728\u4ee3\u7801\u51c6\u5907\u5c31\u7eea\u65f6\u7acb\u5373\u6267\u884c\u5b83\u3002<br \/>\n\u50cf\u8fd9\u6837\uff1a<\/li>\n<\/ul>\n<pre><code class=\"language-js\">function work() { \/*...*\/ }\n\nif (document.readyState == 'loading') {\n  \/\/ \u4ecd\u5728\u52a0\u8f7d\uff0c\u7b49\u5f85\u4e8b\u4ef6\n  document.addEventListener('DOMContentLoaded', work);\n} else {\n  \/\/ DOM \u5df2\u5c31\u7eea\uff01\n  work();\n}\n<\/code><\/pre>\n<p>\u8fd8\u6709\u4e00\u4e2a\u00a0<code>readystatechange<\/code>\u00a0\u4e8b\u4ef6\uff0c\u4f1a\u5728\u72b6\u6001\u53d1\u751f\u6539\u53d8\u65f6\u89e6\u53d1\uff0c\u56e0\u6b64\u6211\u4eec\u53ef\u4ee5\u6253\u5370\u6240\u6709\u8fd9\u4e9b\u72b6\u6001\uff0c\u5c31\u50cf\u8fd9\u6837\uff1a<\/p>\n<pre><code class=\"language-js\">\/\/ \u5f53\u524d\u72b6\u6001\nconsole.log(document.readyState);\n\n\/\/ \u72b6\u6001\u6539\u53d8\u65f6\u6253\u5370\u5b83\ndocument.addEventListener('readystatechange', () =&gt; console.log(document.readyState));\n<\/code><\/pre>\n<p><code>readystatechange<\/code>\u00a0\u4e8b\u4ef6\u662f\u8ddf\u8e2a\u6587\u6863\u52a0\u8f7d\u72b6\u6001\u7684\u53e6\u4e00\u79cd\u673a\u5236\uff0c\u5b83\u5f88\u65e9\u5c31\u5b58\u5728\u4e86\u3002\u73b0\u5728\u5219\u5f88\u5c11\u88ab\u4f7f\u7528\u3002<br \/>\n\u4f46\u662f\u4e3a\u4e86\u5b8c\u6574\u8d77\u89c1\uff0c\u8ba9\u6211\u4eec\u770b\u770b\u5b8c\u6574\u7684\u4e8b\u4ef6\u6d41\u3002<br \/>\n\u8fd9\u662f\u4e00\u4e2a\u5e26\u6709\u00a0<code>&lt;iframe&gt;<\/code>\uff0c<code>&lt;img&gt;<\/code>\u00a0\u548c\u8bb0\u5f55\u4e8b\u4ef6\u7684\u5904\u7406\u7a0b\u5e8f\u7684\u6587\u6863\uff1a<\/p>\n<pre><code class=\"language-html\">&lt;script&gt;\n  log('initial readyState:' + document.readyState);\n\n  document.addEventListener('readystatechange', () =&gt; log('readyState:' + document.readyState));\n  document.addEventListener('DOMContentLoaded', () =&gt; log('DOMContentLoaded'));\n\n  window.onload = () =&gt; log('window onload');\n&lt;\/script&gt;\n\n&lt;iframe src=&quot;iframe.html&quot; onload=&quot;log('iframe onload')&quot;&gt;&lt;\/iframe&gt;\n\n&lt;img src=&quot;http:\/\/en.js.cx\/clipart\/train.gif&quot; id=&quot;img&quot;&gt;\n&lt;script&gt;\n  img.onload = () =&gt; log('img onload');\n&lt;\/script&gt;\n<\/code><\/pre>\n<p>\u6b64\u793a\u4f8b\u8fd0\u884c\u00a0<a href=\"https:\/\/plnkr.co\/edit\/ct5SNvrHCA75b2KZ?p=preview\">\u5728 sandbox \u4e2d<\/a>\u3002<br \/>\n\u5178\u578b\u8f93\u51fa\uff1a<\/p>\n<ol>\n<li>[1] initial readyState:loading<\/li>\n<li>[2] readyState:interactive<\/li>\n<li>[2] DOMContentLoaded<\/li>\n<li>[3] iframe onload<\/li>\n<li>[4] img onload<\/li>\n<li>[4] readyState:complete<\/li>\n<li>[4] window onload<br \/>\n\u65b9\u62ec\u53f7\u4e2d\u7684\u6570\u5b57\u8868\u793a\u53d1\u751f\u8fd9\u79cd\u60c5\u51b5\u7684\u5927\u81f4\u65f6\u95f4\u3002\u6807\u6709\u76f8\u540c\u6570\u5b57\u7684\u4e8b\u4ef6\u51e0\u4e4e\u662f\u540c\u65f6\u53d1\u751f\u7684\uff08\u00b1 \u51e0\u6beb\u79d2\uff09\u3002<\/li>\n<\/ol>\n<ul>\n<li>\u5728\u00a0<code>DOMContentLoaded<\/code>\u00a0\u4e4b\u524d\uff0c<code>document.readyState<\/code>\u00a0\u4f1a\u7acb\u5373\u53d8\u6210\u00a0<code>interactive<\/code>\u3002\u5b83\u4eec\u4fe9\u7684\u610f\u4e49\u5b9e\u9645\u4e0a\u662f\u76f8\u540c\u7684\u3002<\/li>\n<li>\u5f53\u6240\u6709\u8d44\u6e90\uff08<code>iframe<\/code>\u00a0\u548c\u00a0<code>img<\/code>\uff09\u90fd\u52a0\u8f7d\u5b8c\u6210\u540e\uff0c<code>document.readyState<\/code>\u00a0\u53d8\u6210\u00a0<code>complete<\/code>\u3002\u8fd9\u91cc\u6211\u4eec\u53ef\u4ee5\u53d1\u73b0\uff0c\u5b83\u4e0e\u00a0<code>img.onload<\/code>\uff08<code>img<\/code>\u00a0\u662f\u6700\u540e\u4e00\u4e2a\u8d44\u6e90\uff09\u548c\u00a0<code>window.onload<\/code>\u00a0\u51e0\u4e4e\u540c\u65f6\u53d1\u751f\u3002\u8f6c\u6362\u5230\u00a0<code>complete<\/code>\u00a0\u72b6\u6001\u7684\u610f\u4e49\u4e0e\u00a0<code>window.onload<\/code>\u00a0\u76f8\u540c\u3002\u533a\u522b\u5728\u4e8e\u00a0<code>window.onload<\/code>\u00a0\u59cb\u7ec8\u5728\u6240\u6709\u5176\u4ed6\u00a0<code>load<\/code>\u00a0\u5904\u7406\u7a0b\u5e8f\u4e4b\u540e\u8fd0\u884c\u3002<\/li>\n<\/ul>\n<h1>\u811a\u672c async defer<\/h1>\n<p>\u73b0\u4ee3\u7684\u7f51\u7ad9\u4e2d\uff0c\u811a\u672c\u5f80\u5f80\u6bd4 HTML \u66f4\u201c\u91cd\u201d\uff1a\u5b83\u4eec\u7684\u5927\u5c0f\u901a\u5e38\u66f4\u5927\uff0c\u5904\u7406\u65f6\u95f4\u4e5f\u66f4\u957f\u3002<br \/>\n\u5f53\u6d4f\u89c8\u5668\u52a0\u8f7d HTML \u65f6\u9047\u5230\u00a0<code>&lt;script&gt;...&lt;\/script&gt;<\/code>\u00a0\u6807\u7b7e\uff0c\u6d4f\u89c8\u5668\u5c31\u4e0d\u80fd\u7ee7\u7eed\u6784\u5efa DOM\u3002\u5b83\u5fc5\u987b\u7acb\u523b\u6267\u884c\u6b64\u811a\u672c\u3002\u5bf9\u4e8e\u5916\u90e8\u811a\u672c\u00a0<code>&lt;script src=&quot;...&quot;&gt;&lt;\/script&gt;<\/code>\u00a0\u4e5f\u662f\u4e00\u6837\u7684\uff1a\u6d4f\u89c8\u5668\u5fc5\u987b\u7b49\u811a\u672c\u4e0b\u8f7d\u5b8c\uff0c\u5e76\u6267\u884c\u7ed3\u675f\uff0c\u4e4b\u540e\u624d\u80fd\u7ee7\u7eed\u5904\u7406\u5269\u4f59\u7684\u9875\u9762\u3002<br \/>\n\u8fd9\u4f1a\u5bfc\u81f4\u4e24\u4e2a\u91cd\u8981\u7684\u95ee\u9898\uff1a<\/p>\n<ol>\n<li>\u811a\u672c\u4e0d\u80fd\u8bbf\u95ee\u5230\u4f4d\u4e8e\u5b83\u4eec\u4e0b\u9762\u7684 DOM \u5143\u7d20\uff0c\u56e0\u6b64\uff0c\u811a\u672c\u65e0\u6cd5\u7ed9\u5b83\u4eec\u6dfb\u52a0\u5904\u7406\u7a0b\u5e8f\u7b49\u3002<\/li>\n<li>\u5982\u679c\u9875\u9762\u9876\u90e8\u6709\u4e00\u4e2a\u7b28\u91cd\u7684\u811a\u672c\uff0c\u5b83\u4f1a\u201c\u963b\u585e\u9875\u9762\u201d\u3002\u5728\u8be5\u811a\u672c\u4e0b\u8f7d\u5e76\u6267\u884c\u7ed3\u675f\u524d\uff0c\u7528\u6237\u90fd\u4e0d\u80fd\u770b\u5230\u9875\u9762\u5185\u5bb9\uff1a<\/li>\n<\/ol>\n<pre><code class=\"language-html\">&lt;p&gt;...content before script...&lt;\/p&gt;\n\n&lt;script src=&quot;https:\/\/javascript.info\/article\/script-async-defer\/long.js?speed=1&quot;&gt;&lt;\/script&gt;\n\n&lt;!-- This isn't visible until the script loads --&gt;\n&lt;p&gt;...content after script...&lt;\/p&gt;\n<\/code><\/pre>\n<p>\u8fd9\u91cc\u6709\u4e00\u4e9b\u89e3\u51b3\u529e\u6cd5\u3002\u4f8b\u5982\uff0c\u6211\u4eec\u53ef\u4ee5\u628a\u811a\u672c\u653e\u5728\u9875\u9762\u5e95\u90e8\u3002\u6b64\u65f6\uff0c\u5b83\u53ef\u4ee5\u8bbf\u95ee\u5230\u5b83\u4e0a\u9762\u7684\u5143\u7d20\uff0c\u5e76\u4e14\u4e0d\u4f1a\u963b\u585e\u9875\u9762\u663e\u793a\u5185\u5bb9\uff1a<\/p>\n<pre><code class=\"language-html\">&lt;body&gt;\n  ...all content is above the script...\n\n  &lt;script src=&quot;https:\/\/javascript.info\/article\/script-async-defer\/long.js?speed=1&quot;&gt;&lt;\/script&gt;\n&lt;\/body&gt;\n<\/code><\/pre>\n<p>\u4f46\u662f\u8fd9\u79cd\u89e3\u51b3\u65b9\u6848\u8fdc\u975e\u5b8c\u7f8e\u3002\u4f8b\u5982\uff0c\u6d4f\u89c8\u5668\u53ea\u6709\u5728\u4e0b\u8f7d\u4e86\u5b8c\u6574\u7684 HTML \u6587\u6863\u4e4b\u540e\u624d\u4f1a\u6ce8\u610f\u5230\u8be5\u811a\u672c\uff08\u5e76\u4e14\u53ef\u4ee5\u5f00\u59cb\u4e0b\u8f7d\u5b83\uff09\u3002\u5bf9\u4e8e\u957f\u7684 HTML \u6587\u6863\u6765\u8bf4\uff0c\u8fd9\u6837\u53ef\u80fd\u4f1a\u9020\u6210\u660e\u663e\u7684\u5ef6\u8fdf\u3002<br \/>\n\u8fd9\u5bf9\u4e8e\u4f7f\u7528\u9ad8\u901f\u8fde\u63a5\u7684\u4eba\u6765\u8bf4\uff0c\u8fd9\u4e0d\u503c\u4e00\u63d0\uff0c\u4ed6\u4eec\u4e0d\u4f1a\u611f\u53d7\u5230\u8fd9\u79cd\u5ef6\u8fdf\u3002\u4f46\u662f\u8fd9\u4e2a\u4e16\u754c\u4e0a\u4ecd\u7136\u6709\u5f88\u591a\u5730\u533a\u7684\u4eba\u4eec\u6240\u4f7f\u7528\u7684\u7f51\u7edc\u901f\u5ea6\u5f88\u6162\uff0c\u5e76\u4e14\u4f7f\u7528\u7684\u662f\u8fdc\u975e\u5b8c\u7f8e\u7684\u79fb\u52a8\u4e92\u8054\u7f51\u8fde\u63a5\u3002<br \/>\n\u5e78\u8fd0\u7684\u662f\uff0c\u8fd9\u91cc\u6709\u4e24\u4e2a\u00a0<code>&lt;script&gt;<\/code>\u00a0\u7279\u6027\uff08attribute\uff09\u53ef\u4ee5\u4e3a\u6211\u4eec\u89e3\u51b3\u8fd9\u4e2a\u95ee\u9898\uff1a<code>defer<\/code>\u00a0\u548c\u00a0<code>async<\/code>\u3002<\/p>\n<h2>defer<\/h2>\n<p><code>defer<\/code>\u00a0\u7279\u6027\u544a\u8bc9\u6d4f\u89c8\u5668\u4e0d\u8981\u7b49\u5f85\u811a\u672c\u3002\u76f8\u53cd\uff0c\u6d4f\u89c8\u5668\u5c06\u7ee7\u7eed\u5904\u7406 HTML\uff0c\u6784\u5efa DOM\u3002\u811a\u672c\u4f1a\u201c\u5728\u540e\u53f0\u201d\u4e0b\u8f7d\uff0c\u7136\u540e\u7b49 DOM \u6784\u5efa\u5b8c\u6210\u540e\uff0c\u811a\u672c\u624d\u4f1a\u6267\u884c\u3002<br \/>\n\u8fd9\u662f\u4e0e\u4e0a\u9762\u90a3\u4e2a\u76f8\u540c\u7684\u793a\u4f8b\uff0c\u4f46\u662f\u5e26\u6709\u00a0<code>defer<\/code>\u00a0\u7279\u6027\uff1a<\/p>\n<pre><code class=\"language-html\">&lt;p&gt;...content before script...&lt;\/p&gt;\n\n&lt;script defer src=&quot;https:\/\/javascript.info\/article\/script-async-defer\/long.js?speed=1&quot;&gt;&lt;\/script&gt;\n\n&lt;!-- \u7acb\u5373\u53ef\u89c1 --&gt;\n&lt;p&gt;...content after script...&lt;\/p&gt;\n<\/code><\/pre>\n<p>\u6362\u53e5\u8bdd\u8bf4\uff1a<\/p>\n<ul>\n<li>\u5177\u6709\u00a0<code>defer<\/code>\u00a0\u7279\u6027\u7684\u811a\u672c\u4e0d\u4f1a\u963b\u585e\u9875\u9762\u3002<\/li>\n<li>\u5177\u6709\u00a0<code>defer<\/code>\u00a0\u7279\u6027\u7684\u811a\u672c\u603b\u662f\u8981\u7b49\u5230 DOM \u89e3\u6790\u5b8c\u6bd5\uff0c\u4f46\u5728\u00a0<code>DOMContentLoaded<\/code>\u00a0\u4e8b\u4ef6\u4e4b\u524d\u6267\u884c\u3002<br \/>\n\u4e0b\u9762\u8fd9\u4e2a\u793a\u4f8b\u6f14\u793a\u4e86\u4e0a\u9762\u6240\u8bf4\u7684\u7b2c\u4e8c\u53e5\u8bdd\uff1a<\/li>\n<\/ul>\n<pre><code class=\"language-html\">&lt;p&gt;...content before scripts...&lt;\/p&gt;\n\n&lt;script&gt;\n  document.addEventListener('DOMContentLoaded', () =&gt; alert(&quot;DOM ready after defer!&quot;));\n&lt;\/script&gt;\n\n&lt;script defer src=&quot;https:\/\/javascript.info\/article\/script-async-defer\/long.js?speed=1&quot;&gt;&lt;\/script&gt;\n\n&lt;p&gt;...content after scripts...&lt;\/p&gt;\n<\/code><\/pre>\n<ol>\n<li>\u9875\u9762\u5185\u5bb9\u7acb\u5373\u663e\u793a\u3002<\/li>\n<li><code>DOMContentLoaded<\/code>\u00a0\u4e8b\u4ef6\u5904\u7406\u7a0b\u5e8f\u7b49\u5f85\u5177\u6709\u00a0<code>defer<\/code>\u00a0\u7279\u6027\u7684\u811a\u672c\u6267\u884c\u5b8c\u6210\u3002\u5b83\u4ec5\u5728\u811a\u672c\u4e0b\u8f7d\u4e14\u6267\u884c\u7ed3\u675f\u540e\u624d\u4f1a\u88ab\u89e6\u53d1\u3002<br \/>\n<strong>\u5177\u6709\u00a0<code>defer<\/code>\u00a0\u7279\u6027\u7684\u811a\u672c\u4fdd\u6301\u5176\u76f8\u5bf9\u987a\u5e8f\uff0c\u5c31\u50cf\u5e38\u89c4\u811a\u672c\u4e00\u6837\u3002<\/strong><br \/>\n\u5047\u8bbe\uff0c\u6211\u4eec\u6709\u4e24\u4e2a\u5177\u6709\u00a0<code>defer<\/code>\u00a0\u7279\u6027\u7684\u811a\u672c\uff1a<code>long.js<\/code>\u00a0\u5728\u524d\uff0c<code>small.js<\/code>\u00a0\u5728\u540e\u3002<\/li>\n<\/ol>\n<pre><code class=\"language-html\">&lt;script defer src=&quot;https:\/\/javascript.info\/article\/script-async-defer\/long.js&quot;&gt;&lt;\/script&gt;\n&lt;script defer src=&quot;https:\/\/javascript.info\/article\/script-async-defer\/small.js&quot;&gt;&lt;\/script&gt;\n<\/code><\/pre>\n<p>\u6d4f\u89c8\u5668\u626b\u63cf\u9875\u9762\u5bfb\u627e\u811a\u672c\uff0c\u7136\u540e\u5e76\u884c\u4e0b\u8f7d\u5b83\u4eec\uff0c\u4ee5\u63d0\u9ad8\u6027\u80fd\u3002\u56e0\u6b64\uff0c\u5728\u4e0a\u9762\u7684\u793a\u4f8b\u4e2d\uff0c\u4e24\u4e2a\u811a\u672c\u662f\u5e76\u884c\u4e0b\u8f7d\u7684\u3002<code>small.js<\/code>\u00a0\u53ef\u80fd\u4f1a\u5148\u4e0b\u8f7d\u5b8c\u6210\u3002<br \/>\n\u2026\u2026\u4f46\u662f\uff0c<code>defer<\/code>\u00a0\u7279\u6027\u9664\u4e86\u544a\u8bc9\u6d4f\u89c8\u5668\u201c\u4e0d\u8981\u963b\u585e\u9875\u9762\u201d\u4e4b\u5916\uff0c\u8fd8\u53ef\u4ee5\u786e\u4fdd\u811a\u672c\u6267\u884c\u7684\u76f8\u5bf9\u987a\u5e8f\u3002\u56e0\u6b64\uff0c\u5373\u4f7f\u00a0<code>small.js<\/code>\u00a0\u5148\u52a0\u8f7d\u5b8c\u6210\uff0c\u5b83\u4e5f\u9700\u8981\u7b49\u5230\u00a0<code>long.js<\/code>\u00a0\u6267\u884c\u7ed3\u675f\u624d\u4f1a\u88ab\u6267\u884c\u3002<br \/>\n\u5f53\u6211\u4eec\u9700\u8981\u5148\u52a0\u8f7d JavaScript \u5e93\uff0c\u7136\u540e\u518d\u52a0\u8f7d\u4f9d\u8d56\u4e8e\u5b83\u7684\u811a\u672c\u65f6\uff0c\u8fd9\u53ef\u80fd\u4f1a\u5f88\u6709\u7528\u3002<\/p>\n<blockquote>\n<p><code>defer<\/code>\u00a0\u7279\u6027\u4ec5\u9002\u7528\u4e8e\u5916\u90e8\u811a\u672c<br \/>\n\u5982\u679c\u00a0<code>&lt;script&gt;<\/code>\u00a0\u811a\u672c\u6ca1\u6709\u00a0<code>src<\/code>\uff0c\u5219\u4f1a\u5ffd\u7565\u00a0<code>defer<\/code>\u00a0\u7279\u6027\u3002<\/p>\n<\/blockquote>\n<h2>async<\/h2>\n<p><code>async<\/code>\u00a0\u7279\u6027\u4e0e\u00a0<code>defer<\/code>\u00a0\u6709\u4e9b\u7c7b\u4f3c\u3002\u5b83\u4e5f\u80fd\u591f\u8ba9\u811a\u672c\u4e0d\u963b\u585e\u9875\u9762\u3002\u4f46\u662f\uff0c\u5728\u884c\u4e3a\u4e0a\u4e8c\u8005\u6709\u7740\u91cd\u8981\u7684\u533a\u522b\u3002<br \/>\n<code>async<\/code>\u00a0\u7279\u6027\u610f\u5473\u7740\u811a\u672c\u662f\u5b8c\u5168\u72ec\u7acb\u7684\uff1a<\/p>\n<ul>\n<li>\u6d4f\u89c8\u5668\u4e0d\u4f1a\u56e0\u00a0<code>async<\/code>\u00a0\u811a\u672c\u800c\u963b\u585e\uff08\u4e0e\u00a0<code>defer<\/code>\u00a0\u7c7b\u4f3c\uff09\u3002<\/li>\n<li>\u5176\u4ed6\u811a\u672c\u4e0d\u4f1a\u7b49\u5f85\u00a0<code>async<\/code>\u00a0\u811a\u672c\u52a0\u8f7d\u5b8c\u6210\uff0c\u540c\u6837\uff0c<code>async<\/code>\u00a0\u811a\u672c\u4e5f\u4e0d\u4f1a\u7b49\u5f85\u5176\u4ed6\u811a\u672c\u3002<\/li>\n<li><code>DOMContentLoaded<\/code>\u00a0\u548c\u5f02\u6b65\u811a\u672c\u4e0d\u4f1a\u5f7c\u6b64\u7b49\u5f85\uff1a\n<ul>\n<li><code>DOMContentLoaded<\/code>\u00a0\u53ef\u80fd\u4f1a\u53d1\u751f\u5728\u5f02\u6b65\u811a\u672c\u4e4b\u524d\uff08\u5982\u679c\u5f02\u6b65\u811a\u672c\u5728\u9875\u9762\u5b8c\u6210\u540e\u624d\u52a0\u8f7d\u5b8c\u6210\uff09<\/li>\n<li><code>DOMContentLoaded<\/code>\u00a0\u4e5f\u53ef\u80fd\u53d1\u751f\u5728\u5f02\u6b65\u811a\u672c\u4e4b\u540e\uff08\u5982\u679c\u5f02\u6b65\u811a\u672c\u5f88\u77ed\uff0c\u6216\u8005\u662f\u4ece HTTP \u7f13\u5b58\u4e2d\u52a0\u8f7d\u7684\uff09<br \/>\n\u6362\u53e5\u8bdd\u8bf4\uff0c<code>async<\/code>\u00a0\u811a\u672c\u4f1a\u5728\u540e\u53f0\u52a0\u8f7d\uff0c\u5e76\u5728\u52a0\u8f7d\u5c31\u7eea\u65f6\u8fd0\u884c\u3002DOM \u548c\u5176\u4ed6\u811a\u672c\u4e0d\u4f1a\u7b49\u5f85\u5b83\u4eec\uff0c\u5b83\u4eec\u4e5f\u4e0d\u4f1a\u7b49\u5f85\u5176\u5b83\u7684\u4e1c\u897f\u3002<code>async<\/code>\u00a0\u811a\u672c\u5c31\u662f\u4e00\u4e2a\u4f1a\u5728\u52a0\u8f7d\u5b8c\u6210\u65f6\u6267\u884c\u7684\u5b8c\u5168\u72ec\u7acb\u7684\u811a\u672c\u3002\u5c31\u8fd9\u4e48\u7b80\u5355\uff0c\u73b0\u5728\u660e\u767d\u4e86\u5427\uff1f<br \/>\n\u4e0b\u9762\u662f\u4e00\u4e2a\u7c7b\u4f3c\u4e8e\u6211\u4eec\u5728\u8bb2\u00a0<code>defer<\/code>\u00a0\u65f6\u6240\u770b\u5230\u7684\u4f8b\u5b50\uff1a<code>long.js<\/code>\u00a0\u548c\u00a0<code>small.js<\/code>\u00a0\u4e24\u4e2a\u811a\u672c\uff0c\u53ea\u662f\u73b0\u5728\u00a0<code>defer<\/code>\u00a0\u53d8\u6210\u4e86\u00a0<code>async<\/code>\u3002<br \/>\n\u5b83\u4eec\u4e0d\u4f1a\u7b49\u5f85\u5bf9\u65b9\u3002\u5148\u52a0\u8f7d\u5b8c\u6210\u7684\uff08\u53ef\u80fd\u662f\u00a0<code>small.js<\/code>\uff09\u2014\u2014 \u5148\u6267\u884c\uff1a<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<pre><code class=\"language-html\">&lt;p&gt;...content before scripts...&lt;\/p&gt;\n\n&lt;script&gt;\n  document.addEventListener('DOMContentLoaded', () =&gt; alert(&quot;DOM ready!&quot;));\n&lt;\/script&gt;\n\n&lt;script async src=&quot;https:\/\/javascript.info\/article\/script-async-defer\/long.js&quot;&gt;&lt;\/script&gt;\n&lt;script async src=&quot;https:\/\/javascript.info\/article\/script-async-defer\/small.js&quot;&gt;&lt;\/script&gt;\n\n&lt;p&gt;...content after scripts...&lt;\/p&gt;\n<\/code><\/pre>\n<ul>\n<li>\u9875\u9762\u5185\u5bb9\u7acb\u523b\u663e\u793a\u51fa\u6765\uff1a\u52a0\u8f7d\u5199\u6709\u00a0<code>async<\/code>\u00a0\u7684\u811a\u672c\u4e0d\u4f1a\u963b\u585e\u9875\u9762\u6e32\u67d3\u3002<\/li>\n<li><code>DOMContentLoaded<\/code>\u00a0\u53ef\u80fd\u5728\u00a0<code>async<\/code>\u00a0\u4e4b\u524d\u6216\u4e4b\u540e\u89e6\u53d1\uff0c\u4e0d\u80fd\u4fdd\u8bc1\u8c01\u5148\u8c01\u540e\u3002<\/li>\n<li>\u8f83\u5c0f\u7684\u811a\u672c\u00a0<code>small.js<\/code>\u00a0\u6392\u5728\u7b2c\u4e8c\u4f4d\uff0c\u4f46\u53ef\u80fd\u4f1a\u6bd4\u00a0<code>long.js<\/code>\u00a0\u8fd9\u4e2a\u957f\u811a\u672c\u5148\u52a0\u8f7d\u5b8c\u6210\uff0c\u6240\u4ee5\u00a0<code>small.js<\/code>\u00a0\u4f1a\u5148\u6267\u884c\u3002\u867d\u7136\uff0c\u53ef\u80fd\u662f\u00a0<code>long.js<\/code>\u00a0\u5148\u52a0\u8f7d\u5b8c\u6210\uff0c\u5982\u679c\u5b83\u88ab\u7f13\u5b58\u4e86\u7684\u8bdd\uff0c\u90a3\u4e48\u5b83\u5c31\u4f1a\u5148\u6267\u884c\u3002\u6362\u53e5\u8bdd\u8bf4\uff0c\u5f02\u6b65\u811a\u672c\u4ee5\u201c\u52a0\u8f7d\u4f18\u5148\u201d\u7684\u987a\u5e8f\u6267\u884c\u3002<br \/>\n\u5f53\u6211\u4eec\u5c06\u72ec\u7acb\u7684\u7b2c\u4e09\u65b9\u811a\u672c\u96c6\u6210\u5230\u9875\u9762\u65f6\uff0c\u6b64\u65f6\u91c7\u7528\u5f02\u6b65\u52a0\u8f7d\u65b9\u5f0f\u662f\u975e\u5e38\u68d2\u7684\uff1a\u8ba1\u6570\u5668\uff0c\u5e7f\u544a\u7b49\uff0c\u56e0\u4e3a\u5b83\u4eec\u4e0d\u4f9d\u8d56\u4e8e\u6211\u4eec\u7684\u811a\u672c\uff0c\u6211\u4eec\u7684\u811a\u672c\u4e5f\u4e0d\u5e94\u8be5\u7b49\u5f85\u5b83\u4eec\uff1a<\/li>\n<\/ul>\n<pre><code class=\"language-js\">&lt;!-- Google Analytics \u811a\u672c\u901a\u5e38\u662f\u8fd9\u6837\u5d4c\u5165\u9875\u9762\u7684 --&gt;\n&lt;script async src=&quot;https:\/\/google-analytics.com\/analytics.js&quot;&gt;&lt;\/script&gt;\n<\/code><\/pre>\n<blockquote>\n<p><code>async<\/code>\u00a0\u7279\u6027\u4ec5\u9002\u7528\u4e8e\u5916\u90e8\u811a\u672c<br \/>\n\u5c31\u50cf\u00a0<code>defer<\/code>\u00a0\u4e00\u6837\uff0c\u5982\u679c\u00a0<code>&lt;script&gt;<\/code>\u00a0\u6807\u7b7e\u6ca1\u6709\u00a0<code>src<\/code>\u00a0\u7279\u6027\uff08attribute\uff09\uff0c\u90a3\u4e48\u00a0<code>async<\/code>\u00a0\u7279\u6027\u4f1a\u88ab\u5ffd\u7565\u3002<\/p>\n<\/blockquote>\n<h2>\u52a8\u6001\u811a\u672c<\/h2>\n<p>\u6b64\u5916\uff0c\u8fd8\u6709\u4e00\u79cd\u5411\u9875\u9762\u6dfb\u52a0\u811a\u672c\u7684\u91cd\u8981\u7684\u65b9\u5f0f\u3002<br \/>\n\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528 JavaScript \u52a8\u6001\u5730\u521b\u5efa\u4e00\u4e2a\u811a\u672c\uff0c\u5e76\u5c06\u5176\u9644\u52a0\uff08append\uff09\u5230\u6587\u6863\uff08document\uff09\u4e2d\uff1a<\/p>\n<pre><code class=\"language-js\">let script = document.createElement('script');\nscript.src = &quot;\/article\/script-async-defer\/long.js&quot;;\ndocument.body.append(script); \/\/ (*)\n<\/code><\/pre>\n<p>\u5f53\u811a\u672c\u88ab\u9644\u52a0\u5230\u6587\u6863\u00a0<code>(*)<\/code>\u00a0\u65f6\uff0c\u811a\u672c\u5c31\u4f1a\u7acb\u5373\u5f00\u59cb\u52a0\u8f7d\u3002<br \/>\n<strong>\u9ed8\u8ba4\u60c5\u51b5\u4e0b\uff0c\u52a8\u6001\u811a\u672c\u7684\u884c\u4e3a\u662f\u201c\u5f02\u6b65\u201d\u7684\u3002<\/strong><br \/>\n\u4e5f\u5c31\u662f\u8bf4\uff1a<\/p>\n<ul>\n<li>\u5b83\u4eec\u4e0d\u4f1a\u7b49\u5f85\u4efb\u4f55\u4e1c\u897f\uff0c\u4e5f\u6ca1\u6709\u4ec0\u4e48\u4e1c\u897f\u4f1a\u7b49\u5b83\u4eec\u3002<\/li>\n<li>\u5148\u52a0\u8f7d\u5b8c\u6210\u7684\u811a\u672c\u5148\u6267\u884c\uff08\u201c\u52a0\u8f7d\u4f18\u5148\u201d\u987a\u5e8f\uff09\u3002<br \/>\n\u5982\u679c\u6211\u4eec\u663e\u5f0f\u5730\u8bbe\u7f6e\u4e86\u00a0<code>script.async=false<\/code>\uff0c\u5219\u53ef\u4ee5\u6539\u53d8\u8fd9\u4e2a\u89c4\u5219\u3002\u7136\u540e\u811a\u672c\u5c06\u6309\u7167\u811a\u672c\u5728\u6587\u6863\u4e2d\u7684\u987a\u5e8f\u6267\u884c\uff0c\u5c31\u50cf\u00a0<code>defer<\/code>\u00a0\u90a3\u6837\u3002<br \/>\n\u5728\u4e0b\u9762\u8fd9\u4e2a\u4f8b\u5b50\u4e2d\uff0c<code>loadScript(src)<\/code>\u00a0\u51fd\u6570\u6dfb\u52a0\u4e86\u4e00\u4e2a\u811a\u672c\uff0c\u5e76\u5c06\u00a0<code>async<\/code>\u00a0\u8bbe\u7f6e\u4e3a\u4e86\u00a0<code>false<\/code>\u3002<br \/>\n\u56e0\u6b64\uff0c<code>long.js<\/code>\u00a0\u603b\u662f\u4f1a\u5148\u6267\u884c\uff08\u56e0\u4e3a\u5b83\u662f\u5148\u88ab\u6dfb\u52a0\u5230\u6587\u6863\u7684\uff09\uff1a<\/li>\n<\/ul>\n<pre><code class=\"language-js\">function loadScript(src) {\n  let script = document.createElement('script');\n  script.src = src;\n  script.async = false;\n  document.body.append(script);\n}\n\n\/\/ long.js \u5148\u6267\u884c\uff0c\u56e0\u4e3a\u4ee3\u7801\u4e2d\u8bbe\u7f6e\u4e86 async=false\nloadScript(&quot;\/article\/script-async-defer\/long.js&quot;);\nloadScript(&quot;\/article\/script-async-defer\/small.js&quot;);\n<\/code><\/pre>\n<p>\u5982\u679c\u6ca1\u6709\u00a0<code>script.async=false<\/code>\uff0c\u811a\u672c\u5219\u5c06\u4ee5\u9ed8\u8ba4\u89c4\u5219\u6267\u884c\uff0c\u5373\u52a0\u8f7d\u4f18\u5148\u987a\u5e8f\uff08<code>small.js<\/code>\u00a0\u5927\u6982\u4f1a\u5148\u6267\u884c\uff09\u3002<br \/>\n\u540c\u6837\uff0c\u548c\u00a0<code>defer<\/code>\u00a0\u4e00\u6837\uff0c\u5982\u679c\u6211\u4eec\u8981\u52a0\u8f7d\u4e00\u4e2a\u5e93\u548c\u4e00\u4e2a\u4f9d\u8d56\u4e8e\u5b83\u7684\u811a\u672c\uff0c\u90a3\u4e48\u987a\u5e8f\u5c31\u5f88\u91cd\u8981\u3002<\/p>\n<h1>\u8d44\u6e90\u52a0\u8f7d onload onerror<\/h1>\n<p>\u6d4f\u89c8\u5668\u5141\u8bb8\u6211\u4eec\u8ddf\u8e2a\u5916\u90e8\u8d44\u6e90\u7684\u52a0\u8f7d \u2014\u2014 \u811a\u672c\uff0ciframe\uff0c\u56fe\u7247\u7b49\u3002<br \/>\n\u8fd9\u91cc\u6709\u4e24\u4e2a\u4e8b\u4ef6\uff1a<\/p>\n<ul>\n<li><code>onload<\/code>\u00a0\u2014\u2014 \u6210\u529f\u52a0\u8f7d\uff0c<\/li>\n<li><code>onerror<\/code>\u00a0\u2014\u2014 \u51fa\u73b0 error\u3002<\/li>\n<\/ul>\n<h2>\u52a0\u8f7d\u811a\u672c<\/h2>\n<p>\u5047\u8bbe\u6211\u4eec\u9700\u8981\u52a0\u8f7d\u7b2c\u4e09\u65b9\u811a\u672c\uff0c\u5e76\u8c03\u7528\u5176\u4e2d\u7684\u51fd\u6570\u3002<br \/>\n\u6211\u4eec\u53ef\u4ee5\u50cf\u8fd9\u6837\u52a8\u6001\u52a0\u8f7d\u5b83\uff1a<\/p>\n<pre><code class=\"language-js\">let script = document.createElement('script');\nscript.src = &quot;my.js&quot;;\n\ndocument.head.append(script);\n<\/code><\/pre>\n<p>\u2026\u2026\u4f46\u5982\u4f55\u8fd0\u884c\u5728\u8be5\u811a\u672c\u4e2d\u58f0\u660e\u7684\u51fd\u6570\uff1f\u6211\u4eec\u9700\u8981\u7b49\u5230\u8be5\u811a\u672c\u52a0\u8f7d\u5b8c\u6210\uff0c\u4e4b\u540e\u624d\u80fd\u8c03\u7528\u5b83\u3002<\/p>\n<blockquote>\n<p>\u8bf7\u6ce8\u610f\uff1a<br \/>\n\u5bf9\u4e8e\u6211\u4eec\u81ea\u5df1\u7684\u811a\u672c\uff0c\u53ef\u4ee5\u4f7f\u7528\u00a0<a href=\"https:\/\/zh.javascript.info\/modules\">JavaScript module<\/a>\uff0c\u4f46\u662f\u5b83\u4eec\u5e76\u672a\u88ab\u5e7f\u6cdb\u5e94\u7528\u4e8e\u7b2c\u4e09\u65b9\u5e93\u3002<\/p>\n<\/blockquote>\n<h3>script.onload<\/h3>\n<p>\u6211\u4eec\u7684\u5f97\u529b\u52a9\u624b\u662f\u00a0<code>load<\/code>\u00a0\u4e8b\u4ef6\u3002\u5b83\u4f1a\u5728\u811a\u672c\u52a0\u8f7d\u5e76\u6267\u884c\u5b8c\u6210\u65f6\u89e6\u53d1\u3002<\/p>\n<pre><code class=\"language-js\">let script = document.createElement('script');\n\n\/\/ \u53ef\u4ee5\u4ece\u4efb\u610f\u57df\uff08domain\uff09\uff0c\u52a0\u8f7d\u4efb\u610f\u811a\u672c\nscript.src = &quot;https:\/\/cdnjs.cloudflare.com\/ajax\/libs\/lodash.js\/4.3.0\/lodash.js&quot;\ndocument.head.append(script);\n\nscript.onload = function() {\n  \/\/ \u8be5\u811a\u672c\u521b\u5efa\u4e86\u4e00\u4e2a\u53d8\u91cf &quot;_&quot;\n  alert( _.VERSION ); \/\/ \u663e\u793a\u5e93\u7684\u7248\u672c\n};\n<\/code><\/pre>\n<p>\u56e0\u6b64\uff0c\u5728\u00a0<code>onload<\/code>\u00a0\u4e2d\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u811a\u672c\u4e2d\u7684\u53d8\u91cf\uff0c\u8fd0\u884c\u51fd\u6570\u7b49\u3002<br \/>\n\u2026\u2026\u5982\u679c\u52a0\u8f7d\u5931\u8d25\u600e\u4e48\u529e\uff1f\u4f8b\u5982\uff0c\u8fd9\u91cc\u6ca1\u6709\u8fd9\u6837\u7684\u811a\u672c\uff08error 404\uff09\u6216\u8005\u670d\u52a1\u5668\u5b95\u673a\uff08\u4e0d\u53ef\u7528\uff09\u3002<\/p>\n<h3>script.onerror<\/h3>\n<p>\u53d1\u751f\u5728\u811a\u672c\u52a0\u8f7d\u671f\u95f4\u7684 error \u4f1a\u88ab\u00a0<code>error<\/code>\u00a0\u4e8b\u4ef6\u8ddf\u8e2a\u5230\u3002<br \/>\n\u4f8b\u5982\uff0c\u6211\u4eec\u8bf7\u6c42\u4e00\u4e2a\u4e0d\u5b58\u5728\u7684\u811a\u672c\uff1a<\/p>\n<pre><code class=\"language-js\">let script = document.createElement('script');\nscript.src = &quot;https:\/\/example.com\/404.js&quot;; \/\/ \u6ca1\u6709\u8fd9\u4e2a\u811a\u672c\ndocument.head.append(script);\n\nscript.onerror = function() {\n  alert(&quot;Error loading &quot; + this.src); \/\/ Error loading https:\/\/example.com\/404.js\n};\n<\/code><\/pre>\n<p>\u8bf7\u6ce8\u610f\uff0c\u5728\u8fd9\u91cc\u6211\u4eec\u65e0\u6cd5\u83b7\u53d6\u66f4\u591a HTTP error \u7684\u8be6\u7ec6\u4fe1\u606f\u3002\u6211\u4eec\u4e0d\u77e5\u9053 error \u662f 404 \u8fd8\u662f 500 \u6216\u8005\u5176\u4ed6\u60c5\u51b5\u3002\u53ea\u77e5\u9053\u662f\u52a0\u8f7d\u5931\u8d25\u4e86\u3002<\/p>\n<blockquote>\n<p>\u91cd\u8981\uff1a<br \/>\n<code>onload<\/code>\/<code>onerror<\/code>\u00a0\u4e8b\u4ef6\u4ec5\u8ddf\u8e2a\u52a0\u8f7d\u672c\u8eab\u3002<br \/>\n\u5728\u811a\u672c\u5904\u7406\u548c\u6267\u884c\u671f\u95f4\u53ef\u80fd\u53d1\u751f\u7684 error \u8d85\u51fa\u4e86\u8fd9\u4e9b\u4e8b\u4ef6\u8ddf\u8e2a\u7684\u8303\u56f4\u3002\u4e5f\u5c31\u662f\u8bf4\uff1a\u5982\u679c\u811a\u672c\u6210\u529f\u52a0\u8f7d\uff0c\u5219\u5373\u4f7f\u811a\u672c\u4e2d\u6709\u7f16\u7a0b error\uff0c\u4e5f\u4f1a\u89e6\u53d1\u00a0<code>onload<\/code>\u00a0\u4e8b\u4ef6\u3002\u5982\u679c\u8981\u8ddf\u8e2a\u811a\u672c error\uff0c\u53ef\u4ee5\u4f7f\u7528\u00a0<code>window.onerror<\/code>\u00a0\u5168\u5c40\u5904\u7406\u7a0b\u5e8f\u3002<\/p>\n<\/blockquote>\n<h2>\u5176\u4ed6\u8d44\u6e90<\/h2>\n<p><code>load<\/code>\u00a0\u548c\u00a0<code>error<\/code>\u00a0\u4e8b\u4ef6\u4e5f\u9002\u7528\u4e8e\u5176\u4ed6\u8d44\u6e90\uff0c\u57fa\u672c\u4e0a\uff08basically\uff09\u9002\u7528\u4e8e\u5177\u6709\u5916\u90e8\u00a0<code>src<\/code>\u00a0\u7684\u4efb\u4f55\u8d44\u6e90\u3002<br \/>\n\u4f8b\u5982\uff1a<\/p>\n<pre><code class=\"language-js\">let img = document.createElement('img');\nimg.src = &quot;https:\/\/js.cx\/clipart\/train.gif&quot;; \/\/ (*)\n\nimg.onload = function() {\n  alert(`Image loaded, size ${img.width}x${img.height}`);\n};\n\nimg.onerror = function() {\n  alert(&quot;Error occurred while loading image&quot;);\n};\n<\/code><\/pre>\n<p>\u4f46\u662f\u6709\u4e00\u4e9b\u6ce8\u610f\u4e8b\u9879\uff1a<\/p>\n<ul>\n<li>\u5927\u591a\u6570\u8d44\u6e90\u5728\u88ab\u6dfb\u52a0\u5230\u6587\u6863\u4e2d\u540e\uff0c\u4fbf\u5f00\u59cb\u52a0\u8f7d\u3002\u4f46\u662f\u00a0<code>&lt;img&gt;<\/code>\u00a0\u662f\u4e2a\u4f8b\u5916\u3002\u5b83\u8981\u7b49\u5230\u83b7\u5f97 src\u00a0<code>(*)<\/code>\u00a0\u540e\u624d\u5f00\u59cb\u52a0\u8f7d\u3002<\/li>\n<li>\u5bf9\u4e8e\u00a0<code>&lt;iframe&gt;<\/code>\u00a0\u6765\u8bf4\uff0ciframe \u52a0\u8f7d\u5b8c\u6210\u65f6\u4f1a\u89e6\u53d1\u00a0<code>iframe.onload<\/code>\u00a0\u4e8b\u4ef6\uff0c\u65e0\u8bba\u662f\u6210\u529f\u52a0\u8f7d\u8fd8\u662f\u51fa\u73b0 error\u3002<br \/>\n\u8fd9\u662f\u51fa\u4e8e\u5386\u53f2\u539f\u56e0\u3002<\/li>\n<\/ul>\n<h2>\u8de8\u6e90\u7b56\u7565<\/h2>\n<p>\u8fd9\u91cc\u6709\u4e00\u6761\u89c4\u5219\uff1a\u6765\u81ea\u4e00\u4e2a\u7f51\u7ad9\u7684\u811a\u672c\u65e0\u6cd5\u8bbf\u95ee\u5176\u4ed6\u7f51\u7ad9\u7684\u5185\u5bb9\u3002\u4f8b\u5982\uff0c\u4f4d\u4e8e\u00a0<code>https:\/\/facebook.com<\/code>\u00a0\u7684\u811a\u672c\u65e0\u6cd5\u8bfb\u53d6\u4f4d\u4e8e\u00a0<code>https:\/\/gmail.com<\/code>\u00a0\u7684\u7528\u6237\u90ae\u7bb1\u3002<br \/>\n\u6216\u8005\uff0c\u66f4\u786e\u5207\u5730\u8bf4\uff0c\u4e00\u4e2a\u6e90\uff08\u57df\/\u7aef\u53e3\/\u534f\u8bae\u4e09\u8005\uff09\u65e0\u6cd5\u83b7\u53d6\u53e6\u4e00\u4e2a\u6e90\uff08origin\uff09\u7684\u5185\u5bb9\u3002\u56e0\u6b64\uff0c\u5373\u4f7f\u6211\u4eec\u6709\u4e00\u4e2a\u5b50\u57df\uff0c\u6216\u8005\u4ec5\u4ec5\u662f\u53e6\u4e00\u4e2a\u7aef\u53e3\uff0c\u8fd9\u90fd\u662f\u4e0d\u540c\u7684\u6e90\uff0c\u5f7c\u6b64\u65e0\u6cd5\u76f8\u4e92\u8bbf\u95ee\u3002<br \/>\n\u8fd9\u4e2a\u89c4\u5219\u8fd8\u5f71\u54cd\u5176\u4ed6\u57df\u7684\u8d44\u6e90\u3002<br \/>\n\u5982\u679c\u6211\u4eec\u4f7f\u7528\u7684\u662f\u6765\u81ea\u5176\u4ed6\u57df\u7684\u811a\u672c\uff0c\u5e76\u4e14\u8be5\u811a\u672c\u4e2d\u5b58\u5728 error\uff0c\u90a3\u4e48\u6211\u4eec\u65e0\u6cd5\u83b7\u53d6 error \u7684\u8be6\u7ec6\u4fe1\u606f\u3002<br \/>\n\u4f8b\u5982\uff0c\u8ba9\u6211\u4eec\u4f7f\u7528\u4e00\u4e2a\u811a\u672c\u00a0<code>error.js<\/code>\uff0c\u8be5\u811a\u672c\u53ea\u5305\u542b\u4e00\u4e2a\uff08\u9519\u8bef\uff09\u51fd\u6570\u8c03\u7528\uff1a<\/p>\n<pre><code class=\"language-js\">\/\/ \ud83d\udcc1 error.js\nnoSuchFunction();\n<\/code><\/pre>\n<p>\u73b0\u5728\u4ece\u5b83\u6240\u5728\u7684\u540c\u4e00\u4e2a\u7f51\u7ad9\u52a0\u8f7d\u5b83\uff1a<\/p>\n<pre><code class=\"language-html\">&lt;script&gt;\nwindow.onerror = function(message, url, line, col, errorObj) {\n  alert(`${message}\\n${url}, ${line}:${col}`);\n};\n&lt;\/script&gt;\n&lt;script src=&quot;\/article\/onload-onerror\/crossorigin\/error.js&quot;&gt;&lt;\/script&gt;\n<\/code><\/pre>\n<p>\u6211\u4eec\u53ef\u4ee5\u770b\u5230\u4e00\u4e2a\u5f88\u597d\u7684 error \u62a5\u544a\uff0c\u5c31\u50cf\u8fd9\u6837\uff1a<\/p>\n<pre><code class=\"language-Text\">Uncaught ReferenceError: noSuchFunction is not defined\nhttps:\/\/javascript.info\/article\/onload-onerror\/crossorigin\/error.js, 1:1\n<\/code><\/pre>\n<p>\u73b0\u5728\uff0c\u8ba9\u6211\u4eec\u4ece\u53e6\u4e00\u4e2a\u57df\u4e2d\u52a0\u8f7d\u76f8\u540c\u7684\u811a\u672c\uff1a<\/p>\n<pre><code class=\"language-html\">&lt;script&gt;\nwindow.onerror = function(message, url, line, col, errorObj) {\n  alert(`${message}\\n${url}, ${line}:${col}`);\n};\n&lt;\/script&gt;\n&lt;script src=&quot;https:\/\/cors.javascript.info\/article\/onload-onerror\/crossorigin\/error.js&quot;&gt;&lt;\/script&gt;\n<\/code><\/pre>\n<p>\u6b64\u62a5\u544a\u4e0e\u4e0a\u9762\u90a3\u4e2a\u793a\u4f8b\u4e2d\u7684\u4e0d\u540c\uff0c\u5c31\u50cf\u8fd9\u6837\uff1a<\/p>\n<pre><code class=\"language-Text\">Script error.\n, 0:0\n<\/code><\/pre>\n<p>error \u7684\u8be6\u7ec6\u4fe1\u606f\u53ef\u80fd\u56e0\u6d4f\u89c8\u5668\u800c\u5f02\uff0c\u4f46\u662f\u539f\u7406\u662f\u76f8\u540c\u7684\uff1a\u6709\u5173\u811a\u672c\u5185\u90e8\u7684\u4efb\u4f55\u4fe1\u606f\uff08\u5305\u62ec error \u5806\u6808\u8ddf\u8e2a\uff09\u90fd\u88ab\u9690\u85cf\u4e86\u3002\u6b63\u662f\u56e0\u4e3a\u5b83\u6765\u81ea\u4e8e\u53e6\u4e00\u4e2a\u57df\u3002<br \/>\n\u4e3a\u4ec0\u4e48\u6211\u4eec\u9700\u8981 error \u7684\u8be6\u7ec6\u4fe1\u606f\uff1f<br \/>\n\u56e0\u4e3a\u6709\u5f88\u591a\u670d\u52a1\uff08\u6211\u4eec\u4e5f\u53ef\u4ee5\u6784\u5efa\u81ea\u5df1\u7684\u670d\u52a1\uff09\u4f7f\u7528\u00a0<code>window.onerror<\/code>\u00a0\u76d1\u542c\u5168\u5c40 error\uff0c\u4fdd\u5b58 error \u5e76\u63d0\u4f9b\u8bbf\u95ee\u548c\u5206\u6790 error \u7684\u63a5\u53e3\u3002\u8fd9\u5f88\u597d\uff0c\u56e0\u4e3a\u6211\u4eec\u53ef\u4ee5\u770b\u5230\u7531\u7528\u6237\u89e6\u53d1\u7684\u5b9e\u9645\u4e2d\u7684 error\u3002\u4f46\u662f\uff0c\u5982\u679c\u4e00\u4e2a\u811a\u672c\u6765\u81ea\u4e8e\u53e6\u4e00\u4e2a\u6e90\uff08origin\uff09\uff0c\u90a3\u4e48\u6b63\u5982\u6211\u4eec\u521a\u521a\u770b\u5230\u7684\u90a3\u6837\uff0c\u5176\u4e2d\u6ca1\u6709\u592a\u591a\u6709\u5173 error \u7684\u4fe1\u606f\u3002<br \/>\n\u5bf9\u5176\u4ed6\u7c7b\u578b\u7684\u8d44\u6e90\u4e5f\u6267\u884c\u7c7b\u4f3c\u7684\u8de8\u6e90\u7b56\u7565\uff08CORS\uff09\u3002<br \/>\n<strong>\u8981\u5141\u8bb8\u8de8\u6e90\u8bbf\u95ee\uff0c<code>&lt;script&gt;<\/code>\u00a0\u6807\u7b7e\u9700\u8981\u5177\u6709\u00a0<code>crossorigin<\/code>\u00a0\u7279\u6027\uff08attribute\uff09\uff0c\u5e76\u4e14\u8fdc\u7a0b\u670d\u52a1\u5668\u5fc5\u987b\u63d0\u4f9b\u7279\u6b8a\u7684 header\u3002<\/strong><br \/>\n\u8fd9\u91cc\u6709\u4e09\u4e2a\u7ea7\u522b\u7684\u8de8\u6e90\u8bbf\u95ee\uff1a<\/p>\n<ol>\n<li><strong>\u65e0\u00a0<code>crossorigin<\/code>\u00a0\u7279\u6027<\/strong>\u00a0\u2014\u2014 \u7981\u6b62\u8bbf\u95ee\u3002<\/li>\n<li><strong><code>crossorigin=&quot;anonymous&quot;<\/code><\/strong>\u00a0\u2014\u2014 \u5982\u679c\u670d\u52a1\u5668\u7684\u54cd\u5e94\u5e26\u6709\u5305\u542b\u00a0<code>*<\/code>\u00a0\u6216\u6211\u4eec\u7684\u6e90\uff08origin\uff09\u7684 header\u00a0<code>Access-Control-Allow-Origin<\/code>\uff0c\u5219\u5141\u8bb8\u8bbf\u95ee\u3002\u6d4f\u89c8\u5668\u4e0d\u4f1a\u5c06\u6388\u6743\u4fe1\u606f\u548c cookie \u53d1\u9001\u5230\u8fdc\u7a0b\u670d\u52a1\u5668\u3002<\/li>\n<li><strong><code>crossorigin=&quot;use-credentials&quot;<\/code><\/strong>\u00a0\u2014\u2014 \u5982\u679c\u670d\u52a1\u5668\u53d1\u9001\u56de\u5e26\u6709\u6211\u4eec\u7684\u6e90\u7684 header\u00a0<code>Access-Control-Allow-Origin<\/code>\u00a0\u548c\u00a0<code>Access-Control-Allow-Credentials: true<\/code>\uff0c\u5219\u5141\u8bb8\u8bbf\u95ee\u3002\u6d4f\u89c8\u5668\u4f1a\u5c06\u6388\u6743\u4fe1\u606f\u548c cookie \u53d1\u9001\u5230\u8fdc\u7a0b\u670d\u52a1\u5668\u3002<\/li>\n<\/ol>\n<blockquote>\n<p>\u8bf7\u6ce8\u610f\uff1a<br \/>\n\u4f60\u53ef\u4ee5\u5728\u00a0<a href=\"https:\/\/zh.javascript.info\/fetch-crossorigin\">Fetch\uff1a\u8de8\u6e90\u8bf7\u6c42<\/a>\u00a0\u4e00\u7ae0\u4e2d\u4e86\u89e3\u6709\u5173\u8de8\u6e90\u8bbf\u95ee\u7684\u66f4\u591a\u4fe1\u606f\u3002\u8fd9\u4e00\u7ae0\u63cf\u8ff0\u4e86\u7528\u4e8e\u7f51\u7edc\u8bf7\u6c42\u7684\u00a0<code>fetch<\/code>\u00a0\u65b9\u6cd5\uff0c\u4f46\u7b56\u7565\u662f\u5b8c\u5168\u76f8\u540c\u7684\u3002<br \/>\n\u8bf8\u5982 \u201ccookie\u201d \u4e4b\u7c7b\u7684\u5185\u5bb9\u8d85\u51fa\u4e86\u672c\u7ae0\u7684\u8303\u56f4\uff0c\u4f46\u4f60\u53ef\u4ee5\u5728\u00a0<a href=\"https:\/\/zh.javascript.info\/cookie\">Cookie\uff0cdocument.cookie<\/a>\u00a0\u4e00\u7ae0\u5b66\u4e60\u5b83\u4eec\u3002<\/p>\n<\/blockquote>\n<p>\u5728\u6211\u4eec\u7684\u793a\u4f8b\u4e2d\u6ca1\u6709\u4efb\u4f55\u8de8\u6e90\u7279\u6027\uff08attribute\uff09\u3002\u56e0\u6b64\uff0c\u8de8\u6e90\u8bbf\u95ee\u88ab\u7981\u6b62\u3002\u8ba9\u6211\u4eec\u6765\u6dfb\u52a0\u5b83\u5427\u3002<br \/>\n\u6211\u4eec\u53ef\u4ee5\u5728\u00a0<code>&quot;anonymous&quot;<\/code>\uff08\u4e0d\u4f1a\u53d1\u9001 cookie\uff0c\u9700\u8981\u4e00\u4e2a\u670d\u52a1\u5668\u7aef\u7684 header\uff09\u548c\u00a0<code>&quot;use-credentials&quot;<\/code>\uff08\u4f1a\u53d1\u9001 cookie\uff0c\u9700\u8981\u4e24\u4e2a\u670d\u52a1\u5668\u7aef\u7684 header\uff09\u4e4b\u95f4\u8fdb\u884c\u9009\u62e9\u3002<br \/>\n\u5982\u679c\u6211\u4eec\u4e0d\u5173\u5fc3 cookie\uff0c\u90a3\u4e48\u53ef\u4ee5\u9009\u62e9\u00a0<code>&quot;anonymous&quot;<\/code>\uff1a<\/p>\n<pre><code class=\"language-html\">&lt;script&gt;\nwindow.onerror = function(message, url, line, col, errorObj) {\n  alert(`${message}\\n${url}, ${line}:${col}`);\n};\n&lt;\/script&gt;\n&lt;script crossorigin=&quot;anonymous&quot; src=&quot;https:\/\/cors.javascript.info\/article\/onload-onerror\/crossorigin\/error.js&quot;&gt;&lt;\/script&gt;\n<\/code><\/pre>\n<p>\u73b0\u5728\uff0c\u5047\u8bbe\u670d\u52a1\u5668\u63d0\u4f9b\u4e86\u00a0<code>Access-Control-Allow-Origin<\/code>\u00a0header\uff0c\u4e00\u5207\u90fd\u6b63\u5e38\u3002\u6211\u4eec\u6709\u4e86\u5b8c\u6574\u7684 error \u62a5\u544a\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u9875\u9762\u751f\u547d\u5468\u671f DOMContentLoaded load beforeunload unload HTML \u9875 [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[19],"tags":[],"class_list":["post-680","post","type-post","status-publish","format-standard","hentry","category-front-end"],"_links":{"self":[{"href":"https:\/\/levin.ink\/index.php?rest_route=\/wp\/v2\/posts\/680","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/levin.ink\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/levin.ink\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/levin.ink\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/levin.ink\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=680"}],"version-history":[{"count":1,"href":"https:\/\/levin.ink\/index.php?rest_route=\/wp\/v2\/posts\/680\/revisions"}],"predecessor-version":[{"id":681,"href":"https:\/\/levin.ink\/index.php?rest_route=\/wp\/v2\/posts\/680\/revisions\/681"}],"wp:attachment":[{"href":"https:\/\/levin.ink\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=680"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/levin.ink\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=680"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/levin.ink\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=680"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}