{"id":1382,"date":"2022-08-13T01:28:52","date_gmt":"2022-08-12T17:28:52","guid":{"rendered":"https:\/\/blog.cauchyschwarz.com\/?p=1382"},"modified":"2022-08-13T14:49:05","modified_gmt":"2022-08-13T06:49:05","slug":"professional-javascript-for-web-developers-3rd-edition-part-2","status":"publish","type":"post","link":"https:\/\/blog.cauchyschwarz.com\/?p=1382","title":{"rendered":"Professional JavaScript for Web Developers, 3rd Edition, Part 2"},"content":{"rendered":"\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_82_2 ez-toc-wrap-right counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Table of Contents<\/p>\n<label for=\"ez-toc-cssicon-toggle-item-69e0ad8517585\" class=\"ez-toc-cssicon-toggle-label\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/label><input type=\"checkbox\"  id=\"ez-toc-cssicon-toggle-item-69e0ad8517585\" checked aria-label=\"Toggle\" \/><nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-1'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#%E7%AC%AC_3_%E7%AB%A0_%E5%9F%BA%E6%9C%AC%E6%A6%82%E5%BF%B5\" >\u7b2c 3 \u7ae0 \u57fa\u672c\u6982\u5ff5<\/a><ul class='ez-toc-list-level-2' ><li class='ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#1%E8%AF%AD%E6%B3%95\" >1.\u8bed\u6cd5<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#2%E5%85%B3%E9%94%AE%E5%AD%97%E5%92%8C%E4%BF%9D%E7%95%99%E5%AD%97\" >2.\u5173\u952e\u5b57\u548c\u4fdd\u7559\u5b57<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#3%E5%8F%98%E9%87%8F\" >3.\u53d8\u91cf<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#4%E6%95%B0%E6%8D%AE%E7%B1%BB%E5%9E%8B\" >4.\u6570\u636e\u7c7b\u578b<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#1typeof%E6%93%8D%E4%BD%9C%E7%AC%A6\" >1.typeof\u64cd\u4f5c\u7b26<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#2Undefined%E7%B1%BB%E5%9E%8B\" >2.Undefined\u7c7b\u578b<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#3Null%E7%B1%BB%E5%9E%8B\" >3.Null\u7c7b\u578b<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#4Boolean%E7%B1%BB%E5%9E%8B\" >4.Boolean\u7c7b\u578b<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-10\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#5Number%E7%B1%BB%E5%9E%8B\" >5.Number\u7c7b\u578b<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-11\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#6String%E7%B1%BB%E5%9E%8B\" >6.String\u7c7b\u578b<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-12\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#7Object%E7%B1%BB%E5%9E%8B\" >7.Object\u7c7b\u578b<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-13\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#5%E6%93%8D%E4%BD%9C%E7%AC%A6\" >5.\u64cd\u4f5c\u7b26<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-14\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#1%E4%B8%80%E5%85%83%E6%93%8D%E4%BD%9C%E7%AC%A6\" >1.\u4e00\u5143\u64cd\u4f5c\u7b26<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-15\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#2%E4%BD%8D%E6%93%8D%E4%BD%9C%E7%AC%A6\" >2.\u4f4d\u64cd\u4f5c\u7b26<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-16\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#3%E5%B8%83%E5%B0%94%E6%93%8D%E4%BD%9C%E7%AC%A6\" >3.\u5e03\u5c14\u64cd\u4f5c\u7b26<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-17\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#4%E4%B9%98%E6%80%A7%E6%93%8D%E4%BD%9C%E7%AC%A6\" >4.\u4e58\u6027\u64cd\u4f5c\u7b26<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-18\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#5%E5%8A%A0%E6%80%A7%E6%93%8D%E4%BD%9C%E7%AC%A6\" >5.\u52a0\u6027\u64cd\u4f5c\u7b26<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-19\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#6%E5%85%B3%E7%B3%BB%E6%93%8D%E4%BD%9C%E7%AC%A6\" >6.\u5173\u7cfb\u64cd\u4f5c\u7b26<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-20\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#7%E7%9B%B8%E7%AD%89%E6%93%8D%E4%BD%9C%E7%AC%A6\" >7.\u76f8\u7b49\u64cd\u4f5c\u7b26<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-21\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#8%E6%9D%A1%E4%BB%B6%E6%93%8D%E4%BD%9C%E7%AC%A6\" >8.\u6761\u4ef6\u64cd\u4f5c\u7b26<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-22\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#9%E8%B5%8B%E5%80%BC%E6%93%8D%E4%BD%9C%E7%AC%A6\" >9.\u8d4b\u503c\u64cd\u4f5c\u7b26<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-23\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#10%E9%80%97%E5%8F%B7%E6%93%8D%E4%BD%9C%E7%AC%A6\" >10.\u9017\u53f7\u64cd\u4f5c\u7b26<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-24\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#6%E8%AF%AD%E5%8F%A5\" >6.\u8bed\u53e5<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-25\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#1for-in%E8%AF%AD%E5%8F%A5\" >1.for-in\u8bed\u53e5<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-26\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#2label%E8%AF%AD%E5%8F%A5\" >2.label\u8bed\u53e5<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-27\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#3break%E5%92%8Ccontinue%E8%AF%AD%E5%8F%A5\" >3.break\u548ccontinue\u8bed\u53e5<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-28\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#4with%E8%AF%AD%E5%8F%A5\" >4.with\u8bed\u53e5<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-29\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#5switch%E8%AF%AD%E5%8F%A5\" >5.switch\u8bed\u53e5<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-30\" href=\"https:\/\/blog.cauchyschwarz.com\/?p=1382\/#7%E5%87%BD%E6%95%B0\" >7.\u51fd\u6570<\/a><\/li><\/ul><\/li><\/ul><\/nav><\/div>\n<h1 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E7%AC%AC_3_%E7%AB%A0_%E5%9F%BA%E6%9C%AC%E6%A6%82%E5%BF%B5\"><\/span>\u7b2c 3 \u7ae0 \u57fa\u672c\u6982\u5ff5<span class=\"ez-toc-section-end\"><\/span><\/h1>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"1%E8%AF%AD%E6%B3%95\"><\/span>1.\u8bed\u6cd5<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>1.\u53d8\u91cf\u540d\u3001\u51fd\u6570\u3001\u64cd\u4f5c\u7b26\u533a\u5206\u5927\u5c0f\u5199<\/p>\n\n\n\n<p>2.\u6807\u8bc6\u7b26<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>\u7b2c\u4e00\u4e2a\u5b57\u7b26\u5fc5\u987b\u662f\u4e00\u4e2a\u5b57\u6bcd\u3001\u4e0b\u5212\u7ebf\u6216\u4e00\u4e2a\u7f8e\u5143\u7b26\u53f7\uff1b<\/li><li>\u5176\u4ed6\u5b57\u7b26\u53ef\u4ee5\u662f\u5b57\u6bcd\u3001\u4e0b\u5212\u7ebf\u3001\u7f8e\u5143\u7b26\u53f7\u6216\u6570\u5b57\uff1b<\/li><li>\u6807\u8bc6\u7b26\u4e2d\u7684\u5b57\u6bcd\u4e5f\u53ef\u4ee5\u5305\u542b\u6269\u5c55\u7684ASCII\u6216Unicode\u5b57\u6bcd\u5b57\u7b26\u3002<\/li><\/ul>\n\n\n\n<p>3.\u6ce8\u91ca<\/p>\n\n\n\n<p>\u4f7f\u7528\/\/\u6216\/**\/\u4f5c\u4e3a\u6ce8\u91ca\u3002<\/p>\n\n\n\n<p>4.\u4e25\u683c\u6a21\u5f0f<\/p>\n\n\n\n<p>\u53ef\u4ee5\u5728\u811a\u672c\u7684\u5f00\u5934\u6dfb\u52a0<em>&#8220;use strict&#8221;;<\/em>\u8ba9\u6574\u4e2a\u811a\u672c\u542f\u7528\u4e25\u683c\u6a21\u5f0f\uff0c\u6216\u8005\u5728\u51fd\u6570\u5185\u90e8\u4e0a\u65b9\u6dfb\u52a0\u4ee5\u8ba9\u51fd\u6570\u4f7f\u7528\u4e25\u683c\u6a21\u5f0f\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code class=\"\">function doSomething() {\n  \"use strict\";\n  \/\/\u51fd\u6570\u4f53\n}<\/code><\/pre>\n\n\n\n<p>5.\u8bed\u53e5<\/p>\n\n\n\n<p>\u8bed\u53e5\u53ef\u4ee5\u7528\u6216\u8005\u4e0d\u7528<em>\uff1b<\/em>\u4f5c\u4e3a\u7ed3\u5c3e\uff1b<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"2%E5%85%B3%E9%94%AE%E5%AD%97%E5%92%8C%E4%BF%9D%E7%95%99%E5%AD%97\"><\/span>2.\u5173\u952e\u5b57\u548c\u4fdd\u7559\u5b57<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"3%E5%8F%98%E9%87%8F\"><\/span>3.\u53d8\u91cf<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>\u5b9a\u4e49\u53d8\u91cf\u65f6\u53ef\u4ee5\u4f7f\u7528var\u5173\u952e\u5b57\u4e5f\u53ef\u4ee5\u4e0d\u4f7f\u7528\u3002\u4f7f\u7528var\u5173\u952e\u5b57\u7684\u8bdd\u521b\u5efa\u7684\u53d8\u91cf\u4e3a\u5f53\u524d\u4f5c\u7528\u57df\u4e2d\u7684\u5c40\u90e8\u53d8\u91cf\uff0c\u9000\u51fa\u5f53\u524d\u4f5c\u7528\u57df\u8fd9\u4e2a\u53d8\u91cf\u5c31\u9500\u6bc1\u4e86\u3002\u4e0d\u4f7f\u7528var\u5173\u952e\u5b57\u5219\u58f0\u660e\u7684\u662f\u4e00\u4e2a\u5168\u5c40\u53d8\u91cf\uff0c\u9000\u51fa\u5f53\u524d\u4f5c\u7528\u57df\u540e\u4ecd\u7136\u53ef\u4ee5\u8bbf\u95ee\u8fd9\u4e2a\u53d8\u91cf\u3002<\/p>\n\n\n\n<p>\u4e25\u683c\u6a21\u5f0f\u4e0b\u4e0d\u80fd\u5b9a\u4e49\u540d\u4e3aeval\u6216arguments\u7684\u53d8\u91cf\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"4%E6%95%B0%E6%8D%AE%E7%B1%BB%E5%9E%8B\"><\/span>4.\u6570\u636e\u7c7b\u578b<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>5\u79cd\u57fa\u672c\u6570\u636e\u7c7b\u578b\uff1aUndefined\uff0cNull\uff0cBoolean\uff0cNumber\u548cString\u3002<\/p>\n\n\n\n<p>1\u79cd\u590d\u6742\u6570\u636e\u7c7b\u578b\uff0cObject\uff0c\u672c\u8d28\u4e0a\u662f\u4e00\u79cd\u65e0\u5e8f\u7684\u540d\u503c\u5bf9\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"1typeof%E6%93%8D%E4%BD%9C%E7%AC%A6\"><\/span>1.typeof\u64cd\u4f5c\u7b26<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>typeof\u662f\u64cd\u4f5c\u7b26\u800c\u4e0d\u662f\u51fd\u6570\uff0c\u6240\u4ee5\u53ef\u4ee5\u7701\u7565\u62ec\u53f7\u3002<\/p>\n\n\n\n<p>\u8fd4\u56de\u503c<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>&#8216;undefined&#8217;\uff0c\u5982\u679c\u8fd9\u4e2a\u503c\u672a\u5b9a\u4e49(\u58f0\u660e\u4e86\u53d8\u91cf\uff0c\u4f46\u662f\u672a\u8d4b\u4e88\u5177\u4f53\u7684\u503c)\uff1b<\/li><li>&#8216;boolean&#8217;<\/li><li>&#8216;string&#8217;<\/li><li>&#8216;number&#8217;<\/li><li>&#8216;object&#8217;\uff0c\u5982\u679c\u8fd9\u4e2a\u503c\u662f\u5bf9\u8c61\u6216\u8005null\uff0c\u56e0\u4e3anull\u88ab\u8ba4\u4e3a\u662f\u4e00\u4e2a\u7a7a\u7684\u5bf9\u8c61\u7684\u5f15\u7528\uff1b<\/li><li>\u2018function&#8217;\uff0c\u5982\u679c\u8fd9\u4e2a\u5bf9\u8c61\u662f\u51fd\u6570\uff1b<\/li><\/ul>\n\n\n\n<p>\u5728ECMAScript\u4e2d\uff0c\u51fd\u6570\u662f\u5bf9\u8c61\uff0c\u4e0d\u662f\u4e00\u79cd\u6570\u636e\u7c7b\u578b\uff0c\u4f46\u662f\u51fd\u6570\u6709\u4e00\u4e9b\u7279\u6b8a\u7684\u5c5e\u6027\uff0c\u56e0\u6b64typeof\u5c06\u5176\u7279\u522b\u533a\u5206\u4e86\u51fa\u6765\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"2Undefined%E7%B1%BB%E5%9E%8B\"><\/span>2.Undefined\u7c7b\u578b<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>Undefined\u8868\u793a\u58f0\u660e\u4e86\u4f46\u662f\u672a\u521d\u59cb\u5316\u7684\u53d8\u91cf\uff0c\u7528\u6765\u6b63\u5f0f\u533a\u5206\u7a7a\u5bf9\u8c61\u6307\u9488null\u3002<\/p>\n\n\n\n<p>\u672a\u521d\u59cb\u5316\u7684\u53d8\u91cf\u53ea\u80fd\u6267\u884c\u4e00\u9879\u64cd\u4f5c\uff0c\u90a3\u5c31\u662ftypeof\u64cd\u4f5c\u7b26\u3002<\/p>\n\n\n\n<p>\u672a\u58f0\u660e\u7684\u53d8\u91cftypeof\u64cd\u4f5c\u7b26\u4e5f\u4f1a\u8fd4\u56deundefined\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"3Null%E7%B1%BB%E5%9E%8B\"><\/span>3.Null\u7c7b\u578b<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>null\u7528\u6765\u4e13\u95e8\u6307\u4ee3\u8981\u7528\u6765\u4fdd\u5b58\u5bf9\u8c61\uff0c\u4f46\u662f\u8fd8\u672a\u8d4b\u503c\u7684\u7a7a\u6307\u9488\u3002<\/p>\n\n\n\n<p>undefined\u503c\u6d3e\u751f\u81eanull\u503c\uff0c\u56e0\u6b64ECMA-262\u89c4\u5b9a\u5b83\u4eec\u7684\u76f8\u7b49\u6027\u6d4b\u8bd5\u8981\u8fd4\u56detrue\u3002<\/p>\n\n\n\n<p>\u5f53\u4e00\u4e2a\u53d8\u91cf\u662f\u7528\u6765\u4fdd\u5b58\u5bf9\u8c61\u5f15\u7528\u7684\uff0c\u5c31\u5e94\u8be5\u5c06\u5176\u521d\u59cb\u5316\u4e3anull\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"4Boolean%E7%B1%BB%E5%9E%8B\"><\/span>4.Boolean\u7c7b\u578b<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>\u4e00\u5b9a\u8981\u4f7f\u7528true\u548cfalse\uff0c\u5927\u5c0f\u5199\u4e0d\u80fd\u641e\u9519\u3002<\/p>\n\n\n\n<p>\u5404\u79cd\u6570\u636e\u7c7b\u578b\u8f6c\u6362\u4e3aBoolean\u7c7b\u578b\u7684\u89c4\u5219\uff1a<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table><tbody><tr><td>\u6570\u636e\u7c7b\u578b<\/td><td>\u8f6c\u6362\u4e3atrue\u7684\u503c<\/td><td>\u8f6c\u6362\u4e3afalse\u7684\u503c<\/td><\/tr><tr><td>Boolean<\/td><td>true<\/td><td>false<\/td><\/tr><tr><td>String<\/td><td>\u4efb\u4f55\u975e\u7a7a\u5b57\u7b26\u4e32<\/td><td>\u201c\u201d\uff08\u975e\u7a7a\u5b57\u7b26\u4e32\uff09<\/td><\/tr><tr><td>Number<\/td><td>\u4efb\u4f55\u975e\u96f6\u6570\u5b57\u503c(\u5305\u62ec\u65e0\u7a77\u5927)<\/td><td>0\u548cNaN<\/td><\/tr><tr><td>Object<\/td><td>\u4efb\u4f55\u5bf9\u8c61<\/td><td>null<\/td><\/tr><tr><td>Undefined<\/td><td>undefined\u53ea\u6709\u4e00\u4e2a\u503c\uff0c\u53ea\u80fd\u8f6c\u4e3afalse<\/td><td>undefined<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>null\u4e0d\u80fd\u8f6c\u6362\u4e3aBoolean\uff0c\u800cundefined\u53ef\u4ee5\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"5Number%E7%B1%BB%E5%9E%8B\"><\/span>5.Number\u7c7b\u578b<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>\u4e25\u683c\u6a21\u5f0f\u4e0b\u516b\u8fdb\u5236\u5b57\u9762\u91cf\u65e0\u6548\u3002<\/p>\n\n\n\n<p>\u5982\u679c\u6570\u503c\u53ef\u4ee5\u7528\u6574\u578b\u8868\u793a\uff0c\u90a3\u4e48JavaScript\u5f15\u64ce\u4f1a\u5c3d\u91cf\u5c06\u5176\u7528\u6574\u578b\u8868\u793a\u4ee5\u8282\u7701\u7a7a\u95f4\uff1b<\/p>\n\n\n\n<p>\u6240\u4ee5Number\u7684\u5b9e\u73b0\u662f\u4e00\u4e2a32\u4f4dint\u6216\u8005\u4e00\u4e2adouble\u3002<\/p>\n\n\n\n<p>\u7279\u6b8a\u503c\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Number.MIN_VALUE 5e-324<\/li><li>Number.MAX_VALUE 1.7976931348623157e+308<\/li><li>Infinity, -Infinity\uff0c\u8ba1\u7b97\u7ed3\u679c\u7684\u6570\u503c\u5982\u679c\u8d85\u51fa\u4e86\u8fd9\u4e9b\u8303\u56f4\uff0c\u90a3\u4e48\u5c31\u7528Infinity\u6216-Infinity\u8868\u793a\uff1b\u53e6\u5916\u63d0\u4f9bisFinite\u51fd\u6570\u6765\u5224\u65ad\u4e00\u4e2a\u503c\u662f\u5426\u662f\u6709\u9650\u7684\uff1b\u53e6\u5916\u4e5f\u53ef\u4ee5\u4f7f\u7528Number.NEGATIVE_INFINITFY\u548cNumber.POSITIVE_INFINITY\uff1b<\/li><li>NaN\uff0c\u8868\u793a\u4e00\u4e2a\u672c\u6765\u8981\u8fd4\u56de\u6570\u503c\u7684\u64cd\u4f5c\u6570\u672a\u8fd4\u56de\u6570\u503c\u7684\u60c5\u51b5\uff0c\u6bd4\u5982\u4efb\u4f55\u6570\u503c\u9664\u4ee5\u975e\u6570\u503c\u3002\u4efb\u4f55\u6d89\u53caNaN\u7684\u64cd\u4f5c\u7ed3\u679c\u90fd\u4f1a\u8fd4\u56deNaN\u3002\u53ef\u4ee5\u7528isNan\u51fd\u6570\u5224\u65ad\u662f\u5426\u4e3aNaN\uff0c\u4efb\u4f55\u4e0d\u80fd\u88ab\u8f6c\u6362\u4e3a\u6570\u503c\u7684\u503c\u90fd\u4f1a\u88abisNaN\u51fd\u6570\u8fd4\u56defalse\u3002\u5bf9\u4e8eObject\u7c7b\u578b\uff0cisNaN\u4f1a\u5148\u5c1d\u8bd5\u8c03\u7528\u5176valueOf\u65b9\u6cd5\uff0c\u5224\u65ad\u8be5\u51fd\u6570\u8fd4\u56de\u503c\u662f\u5426\u53ef\u4ee5\u8f6c\u6362\u4e3a\u6570\u503c\uff0c\u5982\u679c\u4e0d\u80fd\u518d\u8c03\u7528\u5176toString\u65b9\u6cd5\uff0c\u518d\u6d4b\u8bd5\u5176\u8fd4\u56de\u503c\u662f\u5426\u80fd\u8f6c\u6362\u4e3a\u6570\u503c\u3002<\/li><\/ul>\n\n\n\n<p>\u6570\u503c\u8f6c\u6362<\/p>\n\n\n\n<p>\u67093\u4e2a\u51fd\u6570\u53ef\u4ee5\u628a\u975e\u6570\u503c\u8f6c\u6362\u4e3a\u6570\u503c\uff1aNumber()\uff0cparseInt()\u548cparseFloat()\u3002\u7b2c\u4e00\u4e2a\u51fd\u6570\u53ef\u4ee5\u7528\u4e8e\u4efb\u4f55\u7c7b\u578b\uff0c\u800c\u540e\u4e24\u4e2a\u5219\u4e13\u95e8\u7528\u4e8e\u5b57\u7b26\u4e32\u3002<\/p>\n\n\n\n<p>Number\u51fd\u6570\u7684\u8f6c\u6362\u89c4\u5219\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>\u5bf9\u4e8eBoolean\u8f93\u5165\uff0ctrue\u548cfalse\u5206\u522b\u88ab\u8f6c\u6362\u4e3a1\u548c0\uff1b<\/li><li>\u5bf9\u4e8enull\u8f93\u5165\uff0c\u8fd4\u56de0\uff1b<\/li><li>\u5bf9\u4e8eundefined\uff0c\u8fd4\u56deNaN\uff1b<\/li><li>\u5bf9\u4e8e\u5b57\u7b26\u4e32\uff0c\u5982\u679c\u4e0d\u80fd\u8f6c\u6362\u4e3a\u6570\u5b57\uff0c\u5219\u5c06\u5176\u8f6c\u6362\u4e3aNaN\uff1b<\/li><li>\u5bf9\u4e8e\u5bf9\u8c61\uff0c\u5148\u5c1d\u8bd5\u8f6c\u6362\u5176valueOf\u65b9\u6cd5\u8fd4\u56de\u503c\uff0c\u518d\u5c1d\u8bd5\u8f6c\u6362\u5176toString\u65b9\u6cd5\u8fd4\u56de\u503c\uff1b<\/li><\/ul>\n\n\n\n<p>\u7a7a\u5b57\u7b26\u4e32\u4f1a\u88ab\u8f6c\u6362\u4e3a0\u3002\u7a7a\u5b57\u7b26\u4e32&#8221;\u4e0d\u662fnull\u4e5f\u4e0d\u662fundefined\u3002<\/p>\n\n\n\n<p>\u5bf9\u4e8e&#8217;12blue&#8217;\u8fd9\u79cd\u5b57\u7b26\u4e32\uff0cNumber\u4f1a\u8f6c\u6362\u4e3aNaN\uff0c\u800cparseInt\u4f1a\u8f6c\u6362\u4e3a12\u3002<\/p>\n\n\n\n<p>ECMAScript 3 JavaScript\u5f15\u64ce\u652f\u6301\u516b\u8fdb\u5236\u5b57\u9762\u91cf\uff0c\u800cECMAScript 5 JavaScript\u5f15\u64ce\u4e0d\u652f\u6301\u3002<\/p>\n\n\n\n<p>parseInt\u51fd\u6570\u53ef\u4ee5\u901a\u8fc7\u7b2c\u4e8c\u4e2a\u53c2\u6570\u6765\u6307\u5b9a\u89e3\u6790\u5b57\u9762\u91cf\u65f6\u4f7f\u7528\u7684\u8fdb\u5236\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"6String%E7%B1%BB%E5%9E%8B\"><\/span>6.String\u7c7b\u578b<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>String\u7c7b\u578b\u7528\u4e8e\u8868\u793a\u7531\u96f6\u6216\u591a\u4e2a16\u4f4dUnicode\u5b57\u7b26\u7ec4\u6210\u7684\u5b57\u7b26\u4e32\u5e8f\u5217\u3002<\/p>\n\n\n\n<p>\u8f6c\u4e49\u5e8f\u5217<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>&#8216;\\xnn&#8217; \u4ee5\u5341\u516d\u8fdb\u5236nn\u8868\u793a\u7684\u4e00\u4e2a\u5b57\u7b26\uff0c\u5982&#8217;\\x41&#8217;\u8868\u793a&#8217;A&#8217;<\/li><li>&#8216;\\unnnn&#8217;\u4ee5\u5341\u516d\u8fdb\u5236\u4ee3\u7801nnnn\u8868\u793a\u7684\u4e00\u4e2aUnicode\u5b57\u7b26\uff0c\u5982\\u03a3\u8868\u793a\u5e0c\u814a\u5b57\u6bcd\u03a3\u3002<\/li><\/ul>\n\n\n\n<p>length\u5c5e\u6027\u53ef\u4ee5\u8fd4\u56de\u5b57\u7b26\u4e32\u4e2d\u5b57\u7b26\u6570\u3002<\/p>\n\n\n\n<p>ECMAScript\u4e2d\u7684\u5b57\u7b26\u4e32\u662f\u4e0d\u53ef\u6539\u53d8\u7684\u3002<\/p>\n\n\n\n<p>\u9664\u4e86null\u548cundefined\u65b9\u6cd5\u6ca1\u6709toString\u65b9\u6cd5\uff0c\u5176\u4ed6\u7c7b\u578b\u90fd\u6709toString\u65b9\u6cd5\u3002<\/p>\n\n\n\n<p>String()\u65b9\u6cd5\u5219\u53ef\u4ee5\u5bf9\u4efb\u4f55\u7c7b\u578b\u4f7f\u7528\uff0c\u8be5\u65b9\u6cd5\u4f1a\u8c03\u7528\u8f93\u5165\u5bf9\u8c61\u7684toString\u65b9\u6cd5\uff0c\u5bf9\u4e8enull\u548cundefined\u5219\u4f1a\u5206\u522b\u8fd4\u56de&#8217;null&#8217;\u548c&#8217;undefined&#8217;\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"7Object%E7%B1%BB%E5%9E%8B\"><\/span>7.Object\u7c7b\u578b<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>\u901a\u8fc7new\u64cd\u4f5c\u7b26\u53ef\u4ee5\u521b\u5efa\u65b0\u7684\u5bf9\u8c61\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code class=\"\">var o = new Object();<\/code><\/pre>\n\n\n\n<p>\u5982\u679c\u4e0d\u9700\u8981\u7ed9\u6784\u9020\u51fd\u6570\u4f20\u9012\u53c2\u6570\uff0c\u53ef\u4ee5\u7701\u7565\u6389\u540e\u9762\u7684\u62ec\u53f7\u3002<\/p>\n\n\n\n<p>\u6bcf\u4e2aObject\u7c7b\u578b\u90fd\u5177\u6709\u4e0b\u9762\u7684\u5c5e\u6027\u548c\u65b9\u6cd5\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>constructor\uff0c\u6784\u9020\u51fd\u6570\uff1b<\/li><li>hasOwnProperty(propertyName)\uff0c\u68c0\u67e5\u7ed9\u5b9a\u7684\u5c5e\u6027\u662f\u5426\u5728\u5f53\u524d\u5bf9\u8c61\u5b9e\u4f8b\u4e2d\u5b58\u5728\uff0cpropertyName\u5fc5\u987b\u662f\u4ee5\u5b57\u7b26\u4e32\u5f62\u5f0f\u4f5c\u4e3a\u53c2\u6570\uff1b<\/li><li>isPrototypeOf(object)\uff0c\u68c0\u67e5\u4f20\u5165\u7684\u5bf9\u8c61\u662f\u5426\u662f\u5f53\u524d\u5bf9\u8c61\u7684\u539f\u578b\uff1b<\/li><li>propertyIsEnumerable(propertyName)\uff0c\u68c0\u67e5\u7ed9\u5b9a\u7684\u5c5e\u6027\u662f\u5426\u80fd\u591f\u4f7f\u7528for-in\u8bed\u53e5\uff0cpropertyName\u5fc5\u987b\u662f\u4ee5\u5b57\u7b26\u4e32\u5f62\u5f0f\u4f5c\u4e3a\u53c2\u6570\uff1b<\/li><li>toLocaleString\uff0c\u8fd4\u56de\u5bf9\u8c61\u7684\u5b57\u7b26\u4e32\u8868\u793a\uff0c\u8be5\u5b57\u7b26\u4e32\u4e0e\u6267\u884c\u73af\u5883\u7684\u5730\u533a\u5bf9\u5e94\uff1b<\/li><li>toString\uff0c\u8fd4\u56de\u5bf9\u8c61\u7684\u5b57\u7b26\u4e32\u8868\u793a\uff1b<\/li><li>valueOf\uff0c\u8fd4\u56de\u5bf9\u8c61\u7684\u5b57\u7b26\u4e32\u3001\u6570\u503c\u6216\u5e03\u5c14\u503c\u8868\u793a\u3002\u901a\u5e38\u4e0etoString\u65b9\u6cd5\u8fd4\u56de\u503c\u76f8\u540c\u3002<\/li><\/ul>\n\n\n\n<p>\u5bf9\u4e8eDOM\u548cBOM\u4e2d\u7684\u5bf9\u8c61\uff0c\u4ed6\u4eec\u5c5e\u4e8e\u5bbf\u4e3b\u5bf9\u8c61\uff0c\u7531\u5bbf\u4e3b\u73af\u5883\u63d0\u4f9b\u5b9e\u73b0\u548c\u5b9a\u4e49\uff0c\u4ed6\u4eec\u4e0d\u5c5e\u4e8eECMA-262\u5b9a\u4e49\u7684\u5bf9\u8c61\uff0c\u6240\u4ee5\u5bbf\u4e3b\u5bf9\u8c61\u53ef\u80fd\u4e0d\u4f1a\u7ee7\u627fObject\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"5%E6%93%8D%E4%BD%9C%E7%AC%A6\"><\/span>5.\u64cd\u4f5c\u7b26<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"1%E4%B8%80%E5%85%83%E6%93%8D%E4%BD%9C%E7%AC%A6\"><\/span>1.\u4e00\u5143\u64cd\u4f5c\u7b26<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>\u9012\u589e\u548c\u9012\u51cf\u64cd\u4f5c\u7b26<\/p>\n\n\n\n<p>\u4e00\u5143\u52a0\u548c\u51cf\u64cd\u4f5c\u7b26 \u4e00\u5143\u52a0\u548c\u51cf\u64cd\u4f5c\u7b26\u4f1a\u8fd4\u56de\u4e00\u4e2a\u6570\u503c\u578b\u7684\u7ed3\u679c\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"2%E4%BD%8D%E6%93%8D%E4%BD%9C%E7%AC%A6\"><\/span>2.\u4f4d\u64cd\u4f5c\u7b26<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>JavaScript\u4f1a\u5c06\u6574\u578b\u6570\u503c\u8f6c\u4e3a32\u4f4d\u6709\u7b26\u53f7\u6570\u7136\u540e\u518d\u8fdb\u884c\u4f4d\u64cd\u4f5c\uff0c\u6700\u540e\u5c06\u4f4d\u64cd\u4f5c\u7ed3\u679c\u518d\u8f6c\u4e3adouble\u3002<\/p>\n\n\n\n<p>NaN\u548cInfinity\u4f1a\u88ab\u5f53\u505a0\u5904\u7406\u3002<\/p>\n\n\n\n<p>\u65e0\u7b26\u53f7\u53f3\u79fb&gt;&gt;&gt;<\/p>\n\n\n\n<p>\u6709\u7b26\u53f7\u53f3\u79fb&gt;&gt;<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"3%E5%B8%83%E5%B0%94%E6%93%8D%E4%BD%9C%E7%AC%A6\"><\/span>3.\u5e03\u5c14\u64cd\u4f5c\u7b26<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"4%E4%B9%98%E6%80%A7%E6%93%8D%E4%BD%9C%E7%AC%A6\"><\/span>4.\u4e58\u6027\u64cd\u4f5c\u7b26<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>ECMAScript\u5b9a\u4e49\u4e8c\u697c3\u4e2a\u4e58\u6027\u64cd\u4f5c\u7b26\uff1a\u4e58\u6cd5\u3001\u9664\u6cd5\u548c\u6c42\u6a21\u3002\u5f15\u64ce\u4f1a\u5c06\u975e\u6570\u503c\u7c7b\u578b\u7684\u64cd\u4f5c\u6570\u8f6c\u6362\u4e3a\u6570\u503c\u7c7b\u578b\u3002<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Infinity\u548c0\u76f8\u4e58\u7ed3\u679c\u4f4dNaN\uff1b<\/li><li>Infinify\u9664\u4ee5Infinity\uff0c\u7ed3\u679c\u4e3aNaN\uff1b<\/li><li>0\u96640\uff0c\u7ed3\u679c\u4e3aNaN\uff1b<\/li><li>\u975e\u96f6\u7684\u6709\u9650\u6570\u9664\u4ee5\u96f6\uff0c\u7ed3\u679c\u4e3aInfinitfy\u6216-Infinity\uff1b<\/li><\/ul>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"5%E5%8A%A0%E6%80%A7%E6%93%8D%E4%BD%9C%E7%AC%A6\"><\/span>5.\u52a0\u6027\u64cd\u4f5c\u7b26<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<ul class=\"wp-block-list\"><li>Infinitfy\u52a0-Infinity\uff0c\u7ed3\u679c\u4e3aNaN\uff1b<\/li><li>+0\u52a0-0\uff0c\u7ed3\u679c\u4e3a+0\uff1b<\/li><li>Infinity\u51cfInfinity\uff0c\u7ed3\u679c\u4e3aNaN\uff1b<\/li><li>+0\u51cf+0\uff0c\u7ed3\u679c\u4e3a+0\uff1b<\/li><li>-0\u51cf+0\uff0c\u7ed3\u679c\u4e3a-0\uff1b<\/li><li>-0\u51cf-0\uff0c\u7ed3\u679c\u4e3a+0\uff1b<\/li><\/ul>\n\n\n\n<p><strong>\u5982\u679c\u6709\u4e00\u4e2a\u64cd\u4f5c\u6570\u662f\u5b57\u7b26\u4e32\uff0c\u90a3\u4e48\u4e24\u4e2a\u64cd\u4f5c\u6570\u90fd\u5f97\u8f6c\u6362\u4e3a\u5b57\u7b26\u4e32\u3002<\/strong><\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"6%E5%85%B3%E7%B3%BB%E6%93%8D%E4%BD%9C%E7%AC%A6\"><\/span>6.\u5173\u7cfb\u64cd\u4f5c\u7b26<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>\u64cd\u4f5c\u6570\u4e2d\u6709\u6570\u503c\u7c7b\u578b\u65f6\u9700\u8981\u90fd\u8f6c\u6362\u4e3a\u6570\u503c\u8fdb\u884c\u6bd4\u8f83\uff1b<\/p>\n\n\n\n<p>\u5426\u5219\u6309\u7167\u5b57\u7b26\u4e32\u9010\u4e2a\u5b57\u7b26\u8fdb\u884c\u6bd4\u8f83\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"7%E7%9B%B8%E7%AD%89%E6%93%8D%E4%BD%9C%E7%AC%A6\"><\/span>7.\u76f8\u7b49\u64cd\u4f5c\u7b26<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>\u76f8\u7b49\u548c\u4e0d\u76f8\u7b49\uff0c\u5148\u8f6c\u6362\u518d\u6bd4\u8f83<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>\u6709\u5e03\u5c14\u503c\uff0c\u9700\u8981\u90fd\u8f6c\u6362\u4e3a\u6570\u503c\uff1b<\/li><li>\u4e00\u4e2a\u662f\u5b57\u7b26\u4e32\uff0c\u53e6\u4e00\u4e2a\u662f\u6570\u503c\uff0c\u9700\u8981\u90fd\u8f6c\u4e3a\u6570\u503c\uff1b<\/li><li>\u4e00\u4e2a\u662f\u5bf9\u8c61\uff0c\u53e6\u4e00\u4e2a\u4e0d\u662f\uff0c\u9700\u8981\u8c03\u7528\u5bf9\u8c61\u7684valueOf\u65b9\u6cd5\u518d\u6bd4\u8f83\uff1b<\/li><\/ul>\n\n\n\n<p>\u6bd4\u8f83\u89c4\u5219<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>null \u548cundefined\u76f8\u7b49<\/li><li>\u6bd4\u8f83\u76f8\u7b49\u6027\u4e4b\u524d\uff0c\u4e0d\u80fd\u5c06null\u548cundefined\u8f6c\u4e3a\u5176\u4ed6\u4efb\u4f55\u503c<\/li><li>\u6709NaN\uff0c\u76f8\u7b49\u64cd\u4f5c\u7b26\u8fd4\u56defalse\uff0c\u4e0d\u76f8\u7b49\u64cd\u4f5c\u7b26\u8fd4\u56detrue<\/li><li>\u5982\u679c\u4e24\u4e2a\u6570\u90fd\u662f\u5bf9\u8c61\uff0c\u5219\u6bd4\u8f83\u4ed6\u4eec\u662f\u4e0d\u662f\u540c\u4e00\u4e2a\u5bf9\u8c61\uff0c\u5982\u679c\u90fd\u6307\u5411\u540c\u4e00\u4e2a\u5bf9\u8c61\uff0c\u5219\u76f8\u7b49\u64cd\u4f5c\u7b26\u8fd4\u56detrue\uff0c\u5426\u5219\u8fd4\u56defalse<\/li><\/ul>\n\n\n\n<p>\u5168\u7b49(===)\u548c\u4e0d\u5168\u7b49(!==)\uff0c\u4ec5\u6bd4\u8f83\u800c\u4e0d\u8f6c\u6362<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"8%E6%9D%A1%E4%BB%B6%E6%93%8D%E4%BD%9C%E7%AC%A6\"><\/span>8.\u6761\u4ef6\u64cd\u4f5c\u7b26<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"9%E8%B5%8B%E5%80%BC%E6%93%8D%E4%BD%9C%E7%AC%A6\"><\/span>9.\u8d4b\u503c\u64cd\u4f5c\u7b26<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"10%E9%80%97%E5%8F%B7%E6%93%8D%E4%BD%9C%E7%AC%A6\"><\/span>10.\u9017\u53f7\u64cd\u4f5c\u7b26<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>\u9017\u53f7\u64cd\u4f5c\u7b26\u4f1a\u8fd4\u56de\u8868\u8fbe\u5f0f\u4e2d\u7684\u6700\u540e\u4e00\u9879\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"6%E8%AF%AD%E5%8F%A5\"><\/span>6.\u8bed\u53e5<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"1for-in%E8%AF%AD%E5%8F%A5\"><\/span>1.for-in\u8bed\u53e5<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>\u53ef\u4ee5\u4f7f\u7528for (property in expression) statement\u6216\u8005for (var property in expression) statement\uff0c\u4e3a\u4e86\u4fdd\u8bc1\u4f7f\u7528\u5c40\u90e8\u53d8\u91cf\uff0c\u6700\u597d\u628avar\u52a0\u4e0a\u3002<\/p>\n\n\n\n<p>\u5982\u679c\u8981\u8fed\u4ee3\u7684\u5bf9\u8c61\u7684\u503c\u4e3anull\u6216undefined\uff0cECMAScript\u4e0d\u4f1a\u6267\u884c\u8fd9\u4e2a\u5faa\u73af\u3002\u8001\u65e7\u7248\u672c\u5219\u4f1a\u629b\u51fa\u5f02\u5e38\uff0c\u6240\u4ee5\u4e3a\u4e86\u517c\u5bb9\u6027\u6700\u597d\u5728\u6267\u884c\u4e4b\u524d\u6d4b\u8bd5\u5bf9\u8c61\u662f\u5426\u4e3anull\u6216undefined\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"2label%E8%AF%AD%E5%8F%A5\"><\/span>2.label\u8bed\u53e5<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>\u5b9a\u4e49\u4e00\u4e2abreak\u548ccontinue\u53ef\u4ee5\u8c03\u6574\u7684\u6807\u7b7e\u3002<\/p>\n\n\n\n<p>label: statement<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"3break%E5%92%8Ccontinue%E8%AF%AD%E5%8F%A5\"><\/span>3.break\u548ccontinue\u8bed\u53e5<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>break\u548ccontinue\u53ef\u4ee5\u8054\u5408label\uff0c\u6307\u5b9abreak\/continue\u5916\u5c42\u5faa\u73af\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"javascript\" class=\"language-javascript\">        var num = 0;\n        \n        outermost:\n        for (var i=0; i &lt; 10; i++) {\n             for (var j=0; j &lt; 10; j++) {\n                if (i == 5 &amp;&amp; j == 5) {\n                    break outermost;\n                }\n                num++;\n            }\n        }\n        \n        alert(num);    \/\/55<\/code><\/pre>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"javascript\" class=\"language-javascript\">        var num = 0;\n        \n        outermost:\n        for (var i=0; i &lt; 10; i++) {\n             for (var j=0; j &lt; 10; j++) {\n                if (i == 5 &amp;&amp; j == 5) {\n                    continue outermost;\n                }\n                num++;\n            }\n        }\n        \n        alert(num);    \/\/95<\/code><\/pre>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"4with%E8%AF%AD%E5%8F%A5\"><\/span>4.with\u8bed\u53e5<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>with(expression) statement\uff1b<\/p>\n\n\n\n<p>\u4f7f\u7528with\u8bed\u53e5\u5173\u8054\u5bf9\u8c61\u540e\uff0c\u4ee3\u7801\u7684\u4f5c\u7528\u57df\u88ab\u8bbe\u7f6e\u5230\u8fd9\u4e2a\u7279\u5b9a\u7684\u5bf9\u8c61\u4e2d\uff0c\u4ee3\u7801\u4e2d\u7684\u53d8\u91cf\u5148\u88ab\u8ba4\u4e3a\u662f\u5c40\u90e8\u53d8\u91cf\uff0c\u5982\u679c\u5c40\u90e8\u73af\u5883\u6ca1\u6709\u5b9a\u4e49\u8fd9\u4e2a\u53d8\u91cf\uff0c\u518d\u67e5\u627e\u8fd9\u4e2a\u5bf9\u8c61\u4e2d\u662f\u5426\u6709\u8fd9\u4e2a\u53d8\u91cf\u3002<\/p>\n\n\n\n<p>\u4e25\u683c\u6a21\u5f0f\u4e0d\u5141\u8bb8\u4f7f\u7528with\u8bed\u53e5\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code class=\"\">var qs = location.search.substring(1);\nvar hostName = location.hostname;\nvar url = location.href;<\/code><\/pre>\n\n\n\n<p>\u53ef\u4ee5\u901a\u8fc7with\u8bed\u53e5\u7b80\u5316\u4e3a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code class=\"\">        with(location){\n            var qs = search.substring(1);\n            var hostName = hostname;      \/\/unavailable when viewing from a local file\n            var url = href;\n        }\n<\/code><\/pre>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"5switch%E8%AF%AD%E5%8F%A5\"><\/span>5.switch\u8bed\u53e5<span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p>ECMAScript\u7684switch\u8bed\u53e5\u7279\u8272\u5728\u4e8e\u53ef\u4ee5\u4f7f\u7528\u4efb\u4f55\u7c7b\u578b\uff0c\u751a\u81f3\u53ef\u4ee5\u4f7f\u7528\u8868\u8fbe\u5f0f\u3002<\/p>\n\n\n\n<p>switch\u8bed\u53e5\u5728\u6bd4\u8f83\u503c\u65f6\u4f7f\u7528\u7684\u662f\u5168\u7b49\u64cd\u4f5c\u7b26\uff0c\u56e0\u6b64\u4e0d\u4f1a\u53d1\u751f\u7c7b\u578b\u8f6c\u6362\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"7%E5%87%BD%E6%95%B0\"><\/span>7.\u51fd\u6570<span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>\u4e25\u683c\u6a21\u5f0f\u5bf9\u51fd\u6570\u7684\u9650\u5236\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>\u4e0d\u80fd\u628a\u51fd\u6570\u547d\u540d\u4e3aeval\u6216arguments<\/li><li>\u4e0d\u80fd\u628a\u53c2\u6570\u547d\u540d\u4e3aeval\u6216arguments<\/li><li>\u4e0d\u80fd\u51fa\u73b0\u4e24\u4e2a\u547d\u540d\u53c2\u6570\u540c\u540d\u7684\u60c5\u51b5\uff1b<\/li><\/ul>\n\n\n\n<p>ECMAScript\u51fd\u6570\u5b9a\u4e49\u7684\u53c2\u6570\u4e2a\u6570\u4e0e\u8c03\u7528\u65f6\u4f20\u9012\u7684\u53c2\u6570\u4e2a\u6570\u53ef\u4ee5\u4e0d\u540c\uff0c\u8c03\u7528\u65f6\u4f20\u9012\u7684\u53c2\u6570\u4f1a\u4fdd\u5b58\u5728arguments\u6570\u7ec4\u91cc(\u6570\u7ec4\u957f\u5ea6\u4e0e\u8c03\u7528\u65f6\u4f20\u9012\u7684\u53c2\u6570\u4e2a\u6570\u4e00\u81f4)\u3002\u5728\u51fd\u6570\u5185\u90e8\u53ef\u4ee5\u901a\u8fc7arguments\u6570\u7ec4\u8bbf\u95ee\u51fd\u6570\u53c2\u6570\u5217\u8868\u3002\u901a\u8fc7arguments\u8bbf\u95ee\u7684\u51fd\u6570\u53c2\u6570\u548c\u901a\u8fc7\u547d\u540d\u53c2\u6570\u8bbf\u95ee\u7684\u51fd\u6570\u53c2\u6570\u6548\u679c\u662f\u4e00\u6837\u7684\uff0c\u4ed6\u4eec\u7684\u503c\u603b\u4f1a\u4fdd\u6301\u540c\u6b65(\u4f46\u4ed6\u4eec\u7684\u5185\u5b58\u7a7a\u95f4\u662f\u72ec\u7acb\u7684)\uff0c\u4f46\u662f\u5982\u679c\u8c03\u7528\u65f6\u53ea\u4f20\u4e86\u4e00\u4e2a\u53c2\u6570\uff0c\u90a3\u4e48\u4fee\u6539arguments[1]\u662f\u4e0d\u4f1a\u5c06\u53d8\u5316\u53cd\u6620\u5230\u7b2c\u4e8c\u4e2a\u547d\u540d\u53c2\u6570\u7684\u3002<\/p>\n\n\n\n<p><strong>\u4e25\u683c\u6a21\u5f0f\u4e0b\u5bf9arguments\u7684\u91cd\u5199\u64cd\u4f5c\u65e0\u6548\uff0c\u5373\u5bf9arguments\u7684\u4fee\u6539\u4e0d\u4f1a\u53cd\u6620\u5230\u547d\u540d\u53c2\u6570\u4e0a\u3002<\/strong><\/p>\n\n\n\n<p>\u672a\u4f20\u9012\u503c\u7684\u547d\u540d\u53c2\u6570\u7684\u503c\u9ed8\u8ba4\u4e3aundefined\u3002<\/p>\n\n\n\n<p>ECMAScript\u51fd\u6570\u4e0d\u80fd\u5b9e\u73b0\u91cd\u8f7d\u3002<\/p>\n\n\n\n<p>\u4e24\u4e2a\u540d\u5b57\u76f8\u540c\u7684\u51fd\u6570\uff0c\u540e\u9762\u7684\u51fd\u6570\u4f1a\u8986\u76d6\u6389\u524d\u9762\u7684\u51fd\u6570\u3002<\/p>\n\n\n\n<p><strong><mark style=\"background-color:rgba(0, 0, 0, 0)\" class=\"has-inline-color has-vivid-red-color\">ECMAScript\u4e2d\u7684\u6240\u6709\u53c2\u6570\u4f20\u9012\u7684\u90fd\u662f\u503c\uff0c\u4e0d\u53ef\u80fd\u901a\u8fc7\u5f15\u7528\u4f20\u9012\u53c2\u6570\u3002<\/mark><\/strong><\/p>\n\n\n\n<p>\u8fd9\u4e2a\u6309\u503c\u4f20\u9012\u53c2\u6570\uff0c\u76f8\u5f53\u4e8eECMAScript\u4e0d\u80fd\u5b9e\u73b0C++\u4e2d\u7684\u90a3\u79cd\u901a\u8fc7\u5f15\u7528\u4f20\u9012\u53c2\u6570\u7684\u529f\u80fd\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code class=\"\">int increment(int &amp;x);<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"<p>\u7b2c 3 \u7ae0 \u57fa\u672c\u6982\u5ff5 1.\u8bed\u6cd5 1.\u53d8\u91cf\u540d\u3001\u51fd\u6570\u3001\u64cd\u4f5c\u7b26\u533a\u5206\u5927\u5c0f\u5199 2.\u6807\u8bc6\u7b26 \u7b2c\u4e00\u4e2a\u5b57\u7b26\u5fc5\u987b\u662f\u4e00\u4e2a\u5b57\u6bcd\u3001\u4e0b\u5212\u7ebf\u6216\u4e00\u4e2a\u7f8e\u5143\u7b26\u53f7\uff1b 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