{"id":664,"date":"2024-06-20T11:46:00","date_gmt":"2024-06-20T03:46:00","guid":{"rendered":"https:\/\/levin.ink\/?p=664"},"modified":"2024-06-20T11:46:00","modified_gmt":"2024-06-20T03:46:00","slug":"js-3-9-%e9%94%99%e8%af%af%e5%a4%84%e7%90%86","status":"publish","type":"post","link":"https:\/\/levin.ink\/?p=664","title":{"rendered":"JS – 3-9 \u9519\u8bef\u5904\u7406"},"content":{"rendered":"

\u9519\u8bef\u5904\u7406\uff0c"try...catch"<\/h1>\n

\u4e0d\u7ba1\u4f60\u591a\u4e48\u7cbe\u901a\u7f16\u7a0b\uff0c\u6709\u65f6\u6211\u4eec\u7684\u811a\u672c\u603b\u8fd8\u662f\u4f1a\u51fa\u73b0\u9519\u8bef\u3002\u53ef\u80fd\u662f\u56e0\u4e3a\u6211\u4eec\u7684\u7f16\u5199\u51fa\u9519\uff0c\u6216\u662f\u4e0e\u9884\u671f\u4e0d\u540c\u7684\u7528\u6237\u8f93\u5165\uff0c\u6216\u662f\u9519\u8bef\u7684\u670d\u52a1\u7aef\u54cd\u5e94\u4ee5\u53ca\u5176\u4ed6\u6570\u5343\u79cd\u539f\u56e0\u3002
\n\u901a\u5e38\uff0c\u5982\u679c\u53d1\u751f\u9519\u8bef\uff0c\u811a\u672c\u5c31\u4f1a\u201c\u6b7b\u4ea1\u201d\uff08\u7acb\u5373\u505c\u6b62\uff09\uff0c\u5e76\u5728\u63a7\u5236\u53f0\u5c06\u9519\u8bef\u6253\u5370\u51fa\u6765\u3002
\n\u4f46\u662f\u6709\u4e00\u79cd\u8bed\u6cd5\u7ed3\u6784\u00a0try...catch<\/code>\uff0c\u5b83\u4f7f\u6211\u4eec\u53ef\u4ee5\u201c\u6355\u83b7\uff08catch\uff09\u201d\u9519\u8bef\uff0c\u56e0\u6b64\u811a\u672c\u53ef\u4ee5\u6267\u884c\u66f4\u5408\u7406\u7684\u64cd\u4f5c\uff0c\u800c\u4e0d\u662f\u6b7b\u6389\u3002<\/p>\n

"try...catch" \u8bed\u6cd5<\/h2>\n

try...catch<\/code>\u00a0\u7ed3\u6784\u7531\u4e24\u90e8\u5206\u7ec4\u6210\uff1atry<\/code>\u00a0\u548c\u00a0catch<\/code>\uff1a<\/p>\n

try {\n\n  \/\/ \u4ee3\u7801...\n\n} catch (err) {\n\n  \/\/ \u9519\u8bef\u6355\u83b7\n\n}\n<\/code><\/pre>\n
\u5b83\u6309\u7167\u4ee5\u4e0b\u6b65\u9aa4\u6267\u884c\uff1a<\/p>\n
    \n
  1. \u9996\u5148\uff0c\u6267\u884c\u00a0try {...}<\/code>\u00a0\u4e2d\u7684\u4ee3\u7801\u3002<\/li>\n
  2. \u5982\u679c\u8fd9\u91cc\u6ca1\u6709\u9519\u8bef\uff0c\u5219\u5ffd\u7565\u00a0catch (err)<\/code>\uff1a\u6267\u884c\u5230\u00a0try<\/code>\u00a0\u7684\u672b\u5c3e\u5e76\u8df3\u8fc7\u00a0catch<\/code>\u00a0\u7ee7\u7eed\u6267\u884c\u3002<\/li>\n
  3. \u5982\u679c\u8fd9\u91cc\u51fa\u73b0\u9519\u8bef\uff0c\u5219\u00a0try<\/code>\u00a0\u6267\u884c\u505c\u6b62\uff0c\u63a7\u5236\u6d41\u8f6c\u5411\u00a0catch (err)<\/code>\u00a0\u7684\u5f00\u5934\u3002\u53d8\u91cf\u00a0err<\/code>\uff08\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u4efb\u4f55\u540d\u79f0\uff09\u5c06\u5305\u542b\u4e00\u4e2a error \u5bf9\u8c61\uff0c\u8be5\u5bf9\u8c61\u5305\u542b\u4e86\u6240\u53d1\u751f\u4e8b\u4ef6\u7684\u8be6\u7ec6\u4fe1\u606f\u3002
    \n
    \"Pasted<\/div>
    \n\u6240\u4ee5\uff0ctry {...}<\/code>\u00a0\u5757\u5185\u7684 error \u4e0d\u4f1a\u6740\u6b7b\u811a\u672c \u2014\u2014 \u6211\u4eec\u6709\u673a\u4f1a\u5728\u00a0catch<\/code>\u00a0\u4e2d\u5904\u7406\u5b83\u3002<\/li>\n<\/ol>\n
    \n
    try...catch<\/code>\u00a0\u4ec5\u5bf9\u8fd0\u884c\u65f6\u7684 error \u6709\u6548
    \n\u8981\u4f7f\u5f97\u00a0try...catch<\/code>\u00a0\u80fd\u5de5\u4f5c\uff0c\u4ee3\u7801\u5fc5\u987b\u662f\u53ef\u6267\u884c\u7684\u3002\u6362\u53e5\u8bdd\u8bf4\uff0c\u5b83\u5fc5\u987b\u662f\u6709\u6548\u7684 JavaScript \u4ee3\u7801\u3002
    \n\u5982\u679c\u4ee3\u7801\u5305\u542b\u8bed\u6cd5\u9519\u8bef\uff0c\u90a3\u4e48\u00a0try..catch<\/code>\u00a0\u5c06\u65e0\u6cd5\u6b63\u5e38\u5de5\u4f5c\uff0c\u4f8b\u5982\u542b\u6709\u4e0d\u5339\u914d\u7684\u82b1\u62ec\u53f7\uff1a<\/p>\n<\/blockquote>\n
    try {\n  {{{{{{{{{{{{\n} catch (err) {\n  alert("\u5f15\u64ce\u65e0\u6cd5\u7406\u89e3\u8fd9\u6bb5\u4ee3\u7801\uff0c\u5b83\u662f\u65e0\u6548\u7684");\n}\n<\/code><\/pre>\n
    \n
    JavaScript \u5f15\u64ce\u9996\u5148\u4f1a\u8bfb\u53d6\u4ee3\u7801\uff0c\u7136\u540e\u8fd0\u884c\u5b83\u3002\u5728\u8bfb\u53d6\u9636\u6bb5\u53d1\u751f\u7684\u9519\u8bef\u88ab\u79f0\u4e3a\u201c\u89e3\u6790\u65f6\u95f4\uff08parse-time\uff09\u201d\u9519\u8bef\uff0c\u5e76\u4e14\u65e0\u6cd5\u6062\u590d\uff08\u4ece\u8be5\u4ee3\u7801\u5185\u90e8\uff09\u3002\u8fd9\u662f\u56e0\u4e3a\u5f15\u64ce\u65e0\u6cd5\u7406\u89e3\u8be5\u4ee3\u7801\u3002
    \n\u6240\u4ee5\uff0ctry...catch<\/code>\u00a0\u53ea\u80fd\u5904\u7406\u6709\u6548\u4ee3\u7801\u4e2d\u51fa\u73b0\u7684\u9519\u8bef\u3002\u8fd9\u7c7b\u9519\u8bef\u88ab\u79f0\u4e3a\u201c\u8fd0\u884c\u65f6\u7684\u9519\u8bef\uff08runtime errors\uff09\u201d\uff0c\u6709\u65f6\u88ab\u79f0\u4e3a\u201c\u5f02\u5e38\uff08exceptions\uff09\u201d\u3002<\/p>\n<\/blockquote>\n
    \n
    try...catch<\/code>\u00a0\u540c\u6b65\u6267\u884c
    \n\u5982\u679c\u5728\u201c\u8ba1\u5212\u7684\uff08scheduled\uff09\u201d\u4ee3\u7801\u4e2d\u53d1\u751f\u5f02\u5e38\uff0c\u4f8b\u5982\u5728\u00a0setTimeout<\/code>\u00a0\u4e2d\uff0c\u5219\u00a0try...catch<\/code>\u00a0\u4e0d\u4f1a\u6355\u83b7\u5230\u5f02\u5e38\uff1a<\/p>\n<\/blockquote>\n
    try {\n  setTimeout(function() {\n    noSuchVariable; \/\/ \u811a\u672c\u5c06\u5728\u8fd9\u91cc\u505c\u6b62\u8fd0\u884c\n  }, 1000);\n} catch (err) {\n  alert( "\u4e0d\u5de5\u4f5c" );\n}\n<\/code><\/pre>\n
    \n
    \u56e0\u4e3a\u00a0try...catch<\/code>\u00a0\u5305\u88f9\u4e86\u8ba1\u5212\u8981\u6267\u884c\u7684\u51fd\u6570\uff0c\u8be5\u51fd\u6570\u672c\u8eab\u8981\u7a0d\u540e\u624d\u6267\u884c\uff0c\u8fd9\u65f6\u5f15\u64ce\u5df2\u7ecf\u79bb\u5f00\u4e86\u00a0try...catch<\/code>\u00a0\u7ed3\u6784\u3002
    \n\u4e3a\u4e86\u6355\u83b7\u5230\u8ba1\u5212\u7684\uff08scheduled\uff09\u51fd\u6570\u4e2d\u7684\u5f02\u5e38\uff0c\u90a3\u4e48\u00a0try...catch<\/code>\u00a0\u5fc5\u987b\u5728\u8fd9\u4e2a\u51fd\u6570\u5185\uff1a<\/p>\n<\/blockquote>\n
    setTimeout(function() {\n  try {\n    noSuchVariable; \/\/ try...catch \u5904\u7406 error \u4e86\uff01\n  } catch {\n    alert( "error \u88ab\u5728\u8fd9\u91cc\u6355\u83b7\u4e86\uff01" );\n  }\n}, 1000);\n<\/code><\/pre>\n
    Error\u5bf9\u8c61<\/h2>\n
    \u53d1\u751f\u9519\u8bef\u65f6\uff0cJavaScript \u4f1a\u751f\u6210\u4e00\u4e2a\u5305\u542b\u6709\u5173\u6b64 error \u8be6\u7ec6\u4fe1\u606f\u7684\u5bf9\u8c61\u3002\u7136\u540e\u5c06\u8be5\u5bf9\u8c61\u4f5c\u4e3a\u53c2\u6570\u4f20\u9012\u7ed9\u00a0catch<\/code>\uff1a<\/p>\n
    try {\n  \/\/ ...\n} catch (err) { \/\/ <-- \u201cerror \u5bf9\u8c61\u201d\uff0c\u4e5f\u53ef\u4ee5\u7528\u5176\u4ed6\u53c2\u6570\u540d\u4ee3\u66ff err\n  \/\/ ...\n}\n<\/code><\/pre>\n
    \u5bf9\u4e8e\u6240\u6709\u5185\u5efa\u7684 error\uff0cerror \u5bf9\u8c61\u5177\u6709\u4e24\u4e2a\u4e3b\u8981\u5c5e\u6027\uff1a
    \nname<\/code>
    \nError \u540d\u79f0\u3002\u4f8b\u5982\uff0c\u5bf9\u4e8e\u4e00\u4e2a\u672a\u5b9a\u4e49\u7684\u53d8\u91cf\uff0c\u540d\u79f0\u662f\u00a0"ReferenceError"<\/code>\u3002
    \nmessage<\/code>
    \n\u5173\u4e8e error \u7684\u8be6\u7ec6\u6587\u5b57\u63cf\u8ff0\u3002
    \n\u8fd8\u6709\u5176\u4ed6\u975e\u6807\u51c6\u7684\u5c5e\u6027\u5728\u5927\u591a\u6570\u73af\u5883\u4e2d\u53ef\u7528\u3002\u5176\u4e2d\u88ab\u6700\u5e7f\u6cdb\u4f7f\u7528\u548c\u652f\u6301\u7684\u662f\uff1a
    \nstack<\/code>
    \n\u5f53\u524d\u7684\u8c03\u7528\u6808\uff1a\u7528\u4e8e\u8c03\u8bd5\u76ee\u7684\u7684\u4e00\u4e2a\u5b57\u7b26\u4e32\uff0c\u5176\u4e2d\u5305\u542b\u6709\u5173\u5bfc\u81f4 error \u7684\u5d4c\u5957\u8c03\u7528\u5e8f\u5217\u7684\u4fe1\u606f\u3002<\/p>\n
    try {\n  lalala; \/\/ error, variable is not defined!\n} catch (err) {\n  alert(err.name); \/\/ ReferenceError\n  alert(err.message); \/\/ lalala is not defined\n  alert(err.stack); \/\/ ReferenceError: lalala is not defined at (...call stack)\n\n  \/\/ \u4e5f\u53ef\u4ee5\u5c06\u4e00\u4e2a error \u4f5c\u4e3a\u6574\u4f53\u663e\u793a\u51fa\u6765\n  \/\/ error \u4fe1\u606f\u88ab\u8f6c\u6362\u4e3a\u50cf "name: message" \u8fd9\u6837\u7684\u5b57\u7b26\u4e32\n  alert(err); \/\/ ReferenceError: lalala is not defined\n}\n<\/code><\/pre>\n
    \u53ef\u9009\u7684 "catch" \u7ed1\u5b9a<\/h2>\n
    \n
    \u6700\u8fd1\u65b0\u589e\u7684\u7279\u6027
    \n\u8fd9\u662f\u4e00\u4e2a\u6700\u8fd1\u6dfb\u52a0\u5230 JavaScript \u7684\u7279\u6027\u3002 \u65e7\u5f0f\u6d4f\u89c8\u5668\u53ef\u80fd\u9700\u8981 polyfills.<\/p>\n<\/blockquote>\n
    \u5982\u679c\u6211\u4eec\u4e0d\u9700\u8981 error \u7684\u8be6\u7ec6\u4fe1\u606f\uff0ccatch<\/code>\u00a0\u4e5f\u53ef\u4ee5\u5ffd\u7565\u5b83\uff1a<\/p>\n
    try {\n  \/\/ ...\n} catch { \/\/ <-- \u6ca1\u6709 (err)\n  \/\/ ...\n}\n<\/code><\/pre>\n
    \u4f7f\u7528 "try...catch"<\/h2>\n
    \u8ba9\u6211\u4eec\u4e00\u8d77\u63a2\u7a76\u4e00\u4e0b\u771f\u5b9e\u573a\u666f\u4e2d\u00a0try...catch<\/code>\u00a0\u7684\u7528\u4f8b\u3002
    \n\u6b63\u5982\u6211\u4eec\u6240\u77e5\u9053\u7684\uff0cJavaScript \u652f\u6301\u00a0JSON.parse(str)<\/a>\u00a0\u65b9\u6cd5\u6765\u89e3\u6790 JSON \u7f16\u7801\u7684\u503c\u3002
    \n\u901a\u5e38\uff0c\u5b83\u88ab\u7528\u6765\u89e3\u6790\u4ece\u7f51\u7edc\u3001\u670d\u52a1\u5668\u6216\u662f\u5176\u4ed6\u6765\u6e90\u63a5\u6536\u5230\u7684\u6570\u636e\u3002
    \n\u6211\u4eec\u6536\u5230\u6570\u636e\u540e\uff0c\u7136\u540e\u8c03\u7528\u00a0JSON.parse<\/code>
    \n\u5982\u679c\u00a0json<\/code>\u00a0\u683c\u5f0f\u9519\u8bef\uff0cJSON.parse<\/code>\u00a0\u5c31\u4f1a\u751f\u6210\u4e00\u4e2a error\uff0c\u56e0\u6b64\u811a\u672c\u5c31\u4f1a\u201c\u6b7b\u4ea1\u201d\u3002<\/strong>
    \n\u6211\u4eec\u5bf9\u6b64\u6ee1\u610f\u5417\uff1f\u5f53\u7136\u4e0d\uff01
    \n\u5982\u679c\u8fd9\u6837\u505a\uff0c\u5f53\u62ff\u5230\u7684\u6570\u636e\u51fa\u4e86\u95ee\u9898\uff0c\u90a3\u4e48\u8bbf\u95ee\u8005\u6c38\u8fdc\u90fd\u4e0d\u4f1a\u77e5\u9053\u539f\u56e0\uff08\u9664\u975e\u4ed6\u4eec\u6253\u5f00\u5f00\u53d1\u8005\u63a7\u5236\u53f0\uff09\u3002\u4ee3\u7801\u6267\u884c\u5931\u8d25\u5374\u6ca1\u6709\u63d0\u793a\u4fe1\u606f\uff0c\u8fd9\u771f\u7684\u662f\u5f88\u7cdf\u7cd5\u7684\u7528\u6237\u4f53\u9a8c\u3002
    \n\u8ba9\u6211\u4eec\u7528\u00a0try...catch<\/code>\u00a0\u6765\u5904\u7406\u8fd9\u4e2a error\uff1a<\/p>\n
    let json = "{ bad json }";\n\ntry {\n\n  let user = JSON.parse(json); \/\/ <-- \u5f53\u51fa\u73b0 error \u65f6...\n  alert( user.name ); \/\/ \u4e0d\u5de5\u4f5c\n\n} catch (err) {\n  \/\/ ...\u6267\u884c\u4f1a\u8df3\u8f6c\u5230\u8fd9\u91cc\u5e76\u7ee7\u7eed\u6267\u884c\n  alert( "\u5f88\u62b1\u6b49\uff0c\u6570\u636e\u6709\u9519\u8bef\uff0c\u6211\u4eec\u4f1a\u5c1d\u8bd5\u518d\u8bf7\u6c42\u4e00\u6b21\u3002" );\n  alert( err.name );\n  alert( err.message );\n}\n<\/code><\/pre>\n
    \u5728\u8fd9\u513f\uff0c\u6211\u4eec\u5c06\u00a0catch<\/code>\u00a0\u5757\u4ec5\u4ec5\u7528\u4e8e\u663e\u793a\u4fe1\u606f\uff0c\u4f46\u6211\u4eec\u53ef\u4ee5\u505a\u66f4\u591a\u7684\u4e8b\uff1a\u53d1\u9001\u4e00\u4e2a\u65b0\u7684\u7f51\u7edc\u8bf7\u6c42\uff0c\u5411\u8bbf\u95ee\u8005\u5efa\u8bae\u4e00\u4e2a\u66ff\u4ee3\u65b9\u6848\uff0c\u5c06\u6709\u5173\u9519\u8bef\u7684\u4fe1\u606f\u53d1\u9001\u7ed9\u8bb0\u5f55\u65e5\u5fd7\u7684\u8bbe\u5907\uff0c\u2026\u2026\u3002\u6240\u6709\u8fd9\u4e9b\u90fd\u6bd4\u4ee3\u7801\u201c\u6b7b\u6389\u201d\u597d\u5f97\u591a\u3002<\/p>\n
    \u629b\u51fa\u81ea\u5b9a\u4e49 error<\/h2>\n
    \u5982\u679c\u8fd9\u4e2a\u00a0json<\/code>\u00a0\u5728\u8bed\u6cd5\u4e0a\u662f\u6b63\u786e\u7684\uff0c\u4f46\u662f\u6ca1\u6709\u6240\u5fc5\u987b\u7684\u00a0name<\/code>\u00a0\u5c5e\u6027\u8be5\u600e\u4e48\u529e\uff1f<\/p>\n
    let json = '{ "age": 30 }'; \/\/ \u4e0d\u5b8c\u6574\u7684\u6570\u636e\n\ntry {\n\n  let user = JSON.parse(json); \/\/ <-- \u6ca1\u6709 error\n  alert( user.name ); \/\/ \u6ca1\u6709 name\uff01\n\n} catch (err) {\n  alert( "doesn't execute" );\n}\n<\/code><\/pre>\n
    \u8fd9\u91cc\u00a0JSON.parse<\/code>\u00a0\u6b63\u5e38\u6267\u884c\uff0c\u4f46\u7f3a\u5c11\u00a0name<\/code>\u00a0\u5c5e\u6027\u5bf9\u6211\u4eec\u6765\u8bf4\u786e\u5b9e\u662f\u4e2a error\u3002
    \n\u4e3a\u4e86\u7edf\u4e00\u8fdb\u884c error \u5904\u7406\uff0c\u6211\u4eec\u5c06\u4f7f\u7528\u00a0throw<\/code>\u00a0\u64cd\u4f5c\u7b26\u3002<\/p>\n
    "throw" \u64cd\u4f5c\u7b26<\/h3>\n
    throw<\/code>\u00a0\u64cd\u4f5c\u7b26\u4f1a\u751f\u6210\u4e00\u4e2a error \u5bf9\u8c61\u3002<\/p>\n
    throw <error object>\n<\/code><\/pre>\n
    \u6280\u672f\u4e0a\u8bb2\uff0c\u6211\u4eec\u53ef\u4ee5\u5c06\u4efb\u4f55\u4e1c\u897f\u7528\u4f5c error \u5bf9\u8c61\u3002\u751a\u81f3\u53ef\u4ee5\u662f\u4e00\u4e2a\u539f\u59cb\u7c7b\u578b\u6570\u636e\uff0c\u4f8b\u5982\u6570\u5b57\u6216\u5b57\u7b26\u4e32\uff0c\u4f46\u6700\u597d\u4f7f\u7528\u5bf9\u8c61\uff0c\u6700\u597d\u4f7f\u7528\u5177\u6709\u00a0name<\/code>\u00a0\u548c\u00a0message<\/code>\u00a0\u5c5e\u6027\u7684\u5bf9\u8c61\uff08\u67d0\u79cd\u7a0b\u5ea6\u4e0a\u4fdd\u6301\u4e0e\u5185\u5efa error \u7684\u517c\u5bb9\u6027\uff09\u3002
    \nJavaScript \u4e2d\u6709\u5f88\u591a\u5185\u5efa\u7684\u6807\u51c6 error \u7684\u6784\u9020\u5668\uff1aError<\/code>\uff0cSyntaxError<\/code>\uff0cReferenceError<\/code>\uff0cTypeError<\/code>\u00a0\u7b49\u3002\u6211\u4eec\u4e5f\u53ef\u4ee5\u4f7f\u7528\u5b83\u4eec\u6765\u521b\u5efa error \u5bf9\u8c61\u3002
    \n\u5b83\u4eec\u7684\u8bed\u6cd5\u662f\uff1a<\/p>\n
    let error = new Error(message);\n\/\/ \u6216\nlet error = new SyntaxError(message);\nlet error = new ReferenceError(message);\n\/\/ ...\n<\/code><\/pre>\n
    \u5bf9\u4e8e\u5185\u5efa\u7684 error\uff08\u4e0d\u662f\u5bf9\u4e8e\u5176\u4ed6\u4efb\u4f55\u5bf9\u8c61\uff0c\u4ec5\u4ec5\u662f\u5bf9\u4e8e error\uff09\uff0cname<\/code>\u00a0\u5c5e\u6027\u521a\u597d\u5c31\u662f\u6784\u9020\u5668\u7684\u540d\u5b57\u3002message<\/code>\u00a0\u5219\u6765\u81ea\u4e8e\u53c2\u6570\uff08argument\uff09\u3002<\/p>\n
    let error = new Error("Things happen o_O");\n\nalert(error.name); \/\/ Error\nalert(error.message); \/\/ Things happen o_O\n<\/code><\/pre>\n
    \u8ba9\u6211\u4eec\u6765\u770b\u770b\u00a0JSON.parse<\/code>\u00a0\u4f1a\u751f\u6210\u4ec0\u4e48\u6837\u7684 error\uff1a<\/p>\n
    try {\n  JSON.parse("{ bad json o_O }");\n} catch(err) {\n  alert(err.name); \/\/ SyntaxError\n  alert(err.message); \/\/ Unexpected token b in JSON at position 2\n}\n<\/code><\/pre>\n
    \u6b63\u5982\u6211\u4eec\u6240\u770b\u5230\u7684\uff0c \u90a3\u662f\u4e00\u4e2a\u00a0SyntaxError<\/code>\u3002
    \n\u5728\u6211\u4eec\u7684\u793a\u4f8b\u4e2d\uff0c\u7f3a\u5c11\u00a0name<\/code>\u00a0\u5c5e\u6027\u5c31\u662f\u4e00\u4e2a error\uff0c\u56e0\u4e3a\u7528\u6237\u5fc5\u987b\u6709\u4e00\u4e2a\u00a0name<\/code>\u3002
    \n\u6240\u4ee5\uff0c\u8ba9\u6211\u4eec\u629b\u51fa\u8fd9\u4e2a error\u3002<\/p>\n
    let json = '{ "age": 30 }'; \/\/ \u4e0d\u5b8c\u6574\u7684\u6570\u636e\n\ntry {\n\n  let user = JSON.parse(json); \/\/ <-- \u6ca1\u6709 error\n\n  if (!user.name) {\n    throw new SyntaxError("\u6570\u636e\u4e0d\u5168\uff1a\u6ca1\u6709 name"); \/\/ (*)\n  }\n\n  alert( user.name );\n\n} catch(err) {\n  alert( "JSON Error: " + err.message ); \/\/ JSON Error: \u6570\u636e\u4e0d\u5168\uff1a\u6ca1\u6709 name\n}\n<\/code><\/pre>\n
    \u5728\u00a0(*)<\/code>\u00a0\u6807\u8bb0\u7684\u8fd9\u4e00\u884c\uff0cthrow<\/code>\u00a0\u64cd\u4f5c\u7b26\u751f\u6210\u4e86\u5305\u542b\u7740\u6211\u4eec\u6240\u7ed9\u5b9a\u7684\u00a0message<\/code>\u00a0\u7684\u00a0SyntaxError<\/code>\uff0c\u4e0e JavaScript \u81ea\u5df1\u751f\u6210\u7684\u65b9\u5f0f\u76f8\u540c\u3002try<\/code>\u00a0\u7684\u6267\u884c\u7acb\u5373\u505c\u6b62\uff0c\u63a7\u5236\u6d41\u8f6c\u5411\u00a0catch<\/code>\u00a0\u5757\u3002
    \n\u73b0\u5728\uff0ccatch<\/code>\u00a0\u6210\u4e3a\u4e86\u6240\u6709 error \u5904\u7406\u7684\u552f\u4e00\u573a\u6240\uff1a\u5bf9\u4e8e\u00a0JSON.parse<\/code>\u00a0\u548c\u5176\u4ed6\u60c5\u51b5\u90fd\u9002\u7528\u3002<\/p>\n
    \u518d\u6b21\u629b\u51fa Rethrowing<\/h2>\n
    \u5728\u4e0a\u9762\u7684\u4f8b\u5b50\u4e2d\uff0c\u6211\u4eec\u4f7f\u7528\u00a0try...catch<\/code>\u00a0\u6765\u5904\u7406\u4e0d\u6b63\u786e\u7684\u6570\u636e\u3002\u4f46\u662f\u5728\u00a0try {...}<\/code>\u00a0\u5757\u4e2d\u662f\u5426\u53ef\u80fd\u53d1\u751f\u00a0\u53e6\u4e00\u4e2a\u9884\u6599\u4e4b\u5916\u7684 error<\/strong>\uff1f\u4f8b\u5982\u7f16\u7a0b\u9519\u8bef\uff08\u672a\u5b9a\u4e49\u53d8\u91cf\uff09\u6216\u5176\u4ed6\u9519\u8bef\uff0c\u800c\u4e0d\u4ec5\u4ec5\u662f\u8fd9\u79cd\u201c\u4e0d\u6b63\u786e\u7684\u6570\u636e\u201d\u3002<\/p>\n
    let json = '{ "age": 30 }'; \/\/ \u4e0d\u5b8c\u6574\u7684\u6570\u636e\n\ntry {\n  user = JSON.parse(json); \/\/ <-- \u5fd8\u8bb0\u5728 user \u524d\u653e\u7f6e "let"\n\n  \/\/ ...\n} catch (err) {\n  alert("JSON Error: " + err); \/\/ JSON Error: ReferenceError: user is not defined\n  \/\/ (\u5b9e\u9645\u4e0a\u5e76\u6ca1\u6709 JSON Error)\n}\n<\/code><\/pre>\n
    \u5f53\u7136\uff0c\u4e00\u5207\u7686\u6709\u53ef\u80fd\uff01\u7a0b\u5e8f\u5458\u4e5f\u4f1a\u72af\u9519\u3002\u5373\u4f7f\u662f\u88ab\u6570\u767e\u4e07\u4eba\u4f7f\u7528\u4e86\u51e0\u5341\u5e74\u7684\u5f00\u6e90\u9879\u76ee\u4e2d\uff0c\u4e5f\u53ef\u80fd\u7a81\u7136\u88ab\u53d1\u73b0\u4e86\u4e00\u4e2a\u6f0f\u6d1e\uff0c\u5e76\u5bfc\u81f4\u53ef\u6015\u7684\u9ed1\u5ba2\u5165\u4fb5\u3002
    \n\u5728\u6211\u4eec\u7684\u4f8b\u5b50\u4e2d\uff0ctry...catch<\/code>\u00a0\u65e8\u5728\u6355\u83b7\u201c\u6570\u636e\u4e0d\u6b63\u786e\u201d\u7684 error\u3002\u4f46\u5b9e\u9645\u4e0a\uff0ccatch \u4f1a\u6355\u83b7\u5230\u00a0\u6240\u6709<\/strong>\u00a0\u6765\u81ea\u4e8e\u00a0try<\/code>\u00a0\u7684 error\u3002\u5728\u8fd9\u513f\uff0c\u5b83\u6355\u83b7\u5230\u4e86\u4e00\u4e2a\u9884\u6599\u4e4b\u5916\u7684 error\uff0c\u4f46\u4ecd\u7136\u629b\u51fa\u7684\u662f\u540c\u6837\u7684\u00a0"JSON Error"<\/code>\u00a0\u4fe1\u606f\u3002\u8fd9\u662f\u4e0d\u6b63\u786e\u7684\uff0c\u5e76\u4e14\u4e5f\u4f1a\u4f7f\u4ee3\u7801\u53d8\u5f97\u66f4\u96be\u4ee5\u8c03\u8bd5\u3002
    \n\u4e3a\u4e86\u907f\u514d\u6b64\u7c7b\u95ee\u9898\uff0c\u6211\u4eec\u53ef\u4ee5\u91c7\u7528\u201c\u91cd\u65b0\u629b\u51fa\u201d\u6280\u672f\u3002\u89c4\u5219\u5f88\u7b80\u5355\uff1a
    \ncatch<\/code>\u00a0\u5e94\u8be5\u53ea\u5904\u7406\u5b83\u77e5\u9053\u7684 error\uff0c\u5e76\u201c\u629b\u51fa\u201d\u6240\u6709\u5176\u4ed6 error\u3002<\/strong>
    \n\u201c\u518d\u6b21\u629b\u51fa\uff08rethrowing\uff09\u201d\u6280\u672f\u53ef\u4ee5\u88ab\u66f4\u8be6\u7ec6\u5730\u89e3\u91ca\u4e3a\uff1a<\/p>\n
      \n
    1. Catch \u6355\u83b7\u6240\u6709 error\u3002<\/li>\n
    2. \u5728\u00a0catch (err) {...}<\/code>\u00a0\u5757\u4e2d\uff0c\u6211\u4eec\u5bf9 error \u5bf9\u8c61\u00a0err<\/code>\u00a0\u8fdb\u884c\u5206\u6790\u3002<\/li>\n
    3. \u5982\u679c\u6211\u4eec\u4e0d\u77e5\u9053\u5982\u4f55\u5904\u7406\u5b83\uff0c\u90a3\u6211\u4eec\u5c31\u00a0throw err<\/code>\u3002
      \n\u901a\u5e38\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u00a0instanceof<\/code>\u00a0\u64cd\u4f5c\u7b26\u5224\u65ad\u9519\u8bef\u7c7b\u578b\uff1a<\/li>\n<\/ol>\n
      try {\n  user = { \/*...*\/ };\n} catch (err) {\n  if (err instanceof ReferenceError) {\n    alert('ReferenceError'); \/\/ \u8bbf\u95ee\u4e00\u4e2a\u672a\u5b9a\u4e49\uff08undefined\uff09\u7684\u53d8\u91cf\u4ea7\u751f\u4e86 "ReferenceError"\n  }\n}\n<\/code><\/pre>\n
      \u6211\u4eec\u8fd8\u53ef\u4ee5\u4ece\u00a0err.name<\/code>\u00a0\u5c5e\u6027\u4e2d\u83b7\u53d6\u9519\u8bef\u7684\u7c7b\u540d\u3002\u6240\u6709\u539f\u751f\u7684\u9519\u8bef\u90fd\u6709\u8fd9\u4e2a\u5c5e\u6027\u3002\u53e6\u4e00\u79cd\u65b9\u5f0f\u662f\u8bfb\u53d6\u00a0err.constructor.name<\/code>\u3002
      \n\u5728\u4e0b\u9762\u7684\u4ee3\u7801\u4e2d\uff0c\u6211\u4eec\u4f7f\u7528\u201c\u518d\u6b21\u629b\u51fa\u201d\uff0c\u4ee5\u8fbe\u5230\u5728\u00a0catch<\/code>\u00a0\u4e2d\u53ea\u5904\u7406\u00a0SyntaxError<\/code>\u00a0\u7684\u76ee\u7684\uff1a<\/p>\n
      let json = '{ "age": 30 }'; \/\/ \u4e0d\u5b8c\u6574\u7684\u6570\u636e\ntry {\n\n  let user = JSON.parse(json);\n\n  if (!user.name) {\n    throw new SyntaxError("\u6570\u636e\u4e0d\u5168\uff1a\u6ca1\u6709 name");\n  }\n\n  blabla(); \/\/ \u9884\u6599\u4e4b\u5916\u7684 error\n\n  alert( user.name );\n\n} catch (err) {\n\n  if (err instanceof SyntaxError) {\n    alert( "JSON Error: " + err.message );\n  } else {\n    throw err; \/\/ \u518d\u6b21\u629b\u51fa (*)\n  }\n\n}\n<\/code><\/pre>\n
      \u5982\u679c\u00a0(*)<\/code>\u00a0\u6807\u8bb0\u7684\u8fd9\u884c\u00a0catch<\/code>\u00a0\u5757\u4e2d\u7684 error \u4ece\u00a0try...catch<\/code>\u00a0\u4e2d\u201c\u6389\u4e86\u51fa\u6765\u201d\uff0c\u90a3\u4e48\u5b83\u4e5f\u53ef\u4ee5\u88ab\u5916\u90e8\u7684\u00a0try...catch<\/code>\u00a0\u7ed3\u6784\uff08\u5982\u679c\u5b58\u5728\uff09\u6355\u83b7\u5230\uff0c\u5982\u679c\u5916\u90e8\u4e0d\u5b58\u5728\u8fd9\u79cd\u7ed3\u6784\uff0c\u90a3\u4e48\u811a\u672c\u5c31\u4f1a\u88ab\u6740\u6b7b\u3002
      \n\u6240\u4ee5\uff0ccatch<\/code>\u00a0\u5757\u5b9e\u9645\u4e0a\u53ea\u5904\u7406\u5b83\u77e5\u9053\u8be5\u5982\u4f55\u5904\u7406\u7684 error\uff0c\u5e76\u201c\u8df3\u8fc7\u201d\u6240\u6709\u5176\u4ed6\u7684 error\u3002<\/p>\n
      try...catch...finally<\/h2>\n
      \u7b49\u4e00\u4e0b\uff0c\u4ee5\u4e0a\u5e76\u4e0d\u662f\u6240\u6709\u5185\u5bb9\u3002
      \ntry...catch<\/code>\u00a0\u7ed3\u6784\u53ef\u80fd\u8fd8\u6709\u4e00\u4e2a\u4ee3\u7801\u5b50\u53e5\uff08clause\uff09\uff1afinally<\/code>\u3002
      \n\u5982\u679c\u5b83\u5b58\u5728\uff0c\u5b83\u5728\u6240\u6709\u60c5\u51b5\u4e0b\u90fd\u4f1a\u88ab\u6267\u884c\uff1a<\/p>\n