{"id":1475,"date":"2016-01-31T17:47:58","date_gmt":"2016-01-31T09:47:58","guid":{"rendered":"http:\/\/www.daliane.com\/?p=1475"},"modified":"2016-01-31T17:47:58","modified_gmt":"2016-01-31T09:47:58","slug":"guan_yu_javascript_de_45_ge_ji_qiao","status":"publish","type":"post","link":"http:\/\/www.daliane.com\/category\/jinjiaoyou\/guan_yu_javascript_de_45_ge_ji_qiao\/","title":{"rendered":"\u5173\u4e8ejavascript\u768445\u4e2a\u6280\u5de7"},"content":{"rendered":"<div class=\"entry\">\n<p>\u672c\u6587\u662f\u4e00\u7bc7\u7ffb\u8bd1\u6587\u7ae0\uff0c\u539f\u6587\u4fe1\u606f\u5982\u4e0b\uff1a<\/p>\n<ul>\n<li>\u539f\u6587\uff1a45 Useful JavaScript Tips, Tricks and Best Practices<\/li>\n<li>\u4f5c\u8005\uff1aSaad Mousliki<\/li>\n<\/ul>\n<p>JavaScript\u662f\u4e00\u4e2a\u7edd\u51a0\u5168\u7403\u7684\u7f16\u7a0b\u8bed\u8a00\uff0c\u53ef\u7528\u4e8eWeb\u5f00\u53d1\u3001\u79fb\u52a8\u5e94\u7528\u5f00\u53d1\uff08PhoneGap\u3001Appcelerator\uff09\u3001\u670d\u52a1\u5668\u7aef\u5f00\u53d1\uff08Node.js\u548cWakanda\uff09\u7b49\u7b49\u3002JavaScript\u8fd8\u662f\u5f88\u591a\u65b0\u624b\u8e0f\u5165\u7f16\u7a0b\u4e16\u754c\u7684\u7b2c\u4e00\u4e2a\u8bed\u8a00\u3002\u65e2\u53ef\u4ee5\u7528\u6765\u663e\u793a\u6d4f\u89c8\u5668\u4e2d\u7684\u7b80\u5355\u63d0\u793a\u6846\uff0c\u4e5f\u53ef\u4ee5\u901a\u8fc7nodebot\u6216nodruino\u6765\u63a7\u5236\u673a\u5668\u4eba\u3002\u80fd\u591f\u7f16\u5199\u7ed3\u6784\u6e05\u6670\u3001\u6027\u80fd\u9ad8\u6548\u7684JavaScript\u4ee3\u7801\u7684\u5f00\u53d1\u4eba\u5458\uff0c\u73b0\u5982\u4eca\u5df2\u6210\u4e86\u62db\u8058\u5e02\u573a\u6700\u53d7\u8ffd\u6367\u7684\u4eba\u3002<\/p>\n<p>\u5728\u8fd9\u7bc7\u6587\u7ae0\u91cc\uff0c\u6211\u5c06\u5206\u4eab\u4e00\u4e9bJavaScript\u7684\u6280\u5de7\u3001\u79d8\u8bc0\u548c\u6700\u4f73\u5b9e\u8df5\uff0c\u9664\u4e86\u5c11\u6570\u51e0\u4e2a\u5916\uff0c\u4e0d\u7ba1\u662f\u6d4f\u89c8\u5668\u7684JavaScript\u5f15\u64ce\uff0c\u8fd8\u662f\u670d\u52a1\u5668\u7aefJavaScript\u89e3\u91ca\u5668\uff0c\u5747\u9002\u7528\u3002<\/p>\n<p>\u672c\u6587\u4e2d\u7684\u793a\u4f8b\u4ee3\u7801\uff0c\u901a\u8fc7\u4e86\u5728Google Chrome 30\u6700\u65b0\u7248\uff08V8 3.20.17.15\uff09\u4e0a\u7684\u6d4b\u8bd5\u3002<\/p>\n<p>&nbsp;<\/p>\n<h3 id=\"1\u3001\u9996\u6b21\u4e3a\u53d8\u91cf\u8d4b\u503c\u65f6\u52a1\u5fc5\u4f7f\u7528var\u5173\u952e\u5b57\">1\u3001\u9996\u6b21\u4e3a\u53d8\u91cf\u8d4b\u503c\u65f6\u52a1\u5fc5\u4f7f\u7528<code>var<\/code>\u5173\u952e\u5b57<\/h3>\n<p>\u53d8\u91cf\u6ca1\u6709\u58f0\u660e\u800c\u76f4\u63a5\u8d4b\u503c\u5f97\u8bdd\uff0c\u9ed8\u8ba4\u4f1a\u4f5c\u4e3a\u4e00\u4e2a\u65b0\u7684\u5168\u5c40\u53d8\u91cf\uff0c\u8981\u5c3d\u91cf\u907f\u514d\u4f7f\u7528\u5168\u5c40\u53d8\u91cf\u3002<\/p>\n<h3 id=\"2\u3001\u4f7f\u7528===\u53d6\u4ee3==\">2\u3001\u4f7f\u7528<code>===<\/code>\u53d6\u4ee3<code>==<\/code><\/h3>\n<p><code>==<\/code>\u548c<code>!=<\/code>\u64cd\u4f5c\u7b26\u4f1a\u5728\u9700\u8981\u7684\u60c5\u51b5\u4e0b\u81ea\u52a8\u8f6c\u6362\u6570\u636e\u7c7b\u578b\u3002\u4f46<code>===<\/code>\u548c<code>!==<\/code>\u4e0d\u4f1a\uff0c\u5b83\u4eec\u4f1a\u540c\u65f6\u6bd4\u8f83\u503c\u548c\u6570\u636e\u7c7b\u578b\uff0c\u8fd9\u4e5f\u4f7f\u5f97\u5b83\u4eec\u8981\u6bd4<code>==<\/code>\u548c<code>!=<\/code>\u5feb\u3002<\/p>\n<figure class=\"highlight javascript\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<div class=\"line\">4<\/div>\n<div class=\"line\">5<\/div>\n<div class=\"line\">6<\/div>\n<div class=\"line\">7<\/div>\n<div class=\"line\">8<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\">[<span class=\"number\">10<\/span>] === <span class=\"number\">10<\/span> <span class=\"comment\">\/\/ is false<\/span><\/div>\n<div class=\"line\">[<span class=\"number\">10<\/span>] == <span class=\"number\">10<\/span> <span class=\"comment\">\/\/ is true<\/span><\/div>\n<div class=\"line\"><span class=\"string\">\u201910\u2019<\/span> == <span class=\"number\">10<\/span> <span class=\"comment\">\/\/ is true<\/span><\/div>\n<div class=\"line\"><span class=\"string\">\u201910\u2019<\/span> === <span class=\"number\">10<\/span> <span class=\"comment\">\/\/ is false<\/span><\/div>\n<div class=\"line\">[] == <span class=\"number\">0<\/span> <span class=\"comment\">\/\/ is true<\/span><\/div>\n<div class=\"line\">[] === <span class=\"number\">0<\/span> <span class=\"comment\">\/\/ is false<\/span><\/div>\n<div class=\"line\"><span class=\"string\">\u201d<\/span> == <span class=\"literal\">false<\/span> <span class=\"comment\">\/\/ is true but true == \u201ca\u201d is false<\/span><\/div>\n<div class=\"line\"><span class=\"string\">\u201d<\/span> === <span class=\"literal\">false<\/span> <span class=\"comment\">\/\/ is false<\/span><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"3\u3001underfined\u3001null\u30010\u3001false\u3001NaN\u3001\u7a7a\u5b57\u7b26\u4e32\u7684\u903b\u8f91\u7ed3\u679c\u5747\u4e3afalse\">3\u3001<code>underfined<\/code>\u3001<code>null<\/code>\u30010\u3001false\u3001NaN\u3001\u7a7a\u5b57\u7b26\u4e32\u7684\u903b\u8f91\u7ed3\u679c\u5747\u4e3afalse<\/h3>\n<h3 id=\"4\u3001\u884c\u5c3e\u4f7f\u7528\u5206\u53f7\">4\u3001\u884c\u5c3e\u4f7f\u7528\u5206\u53f7<\/h3>\n<p>\u5b9e\u8df5\u4e2d\u6700\u597d\u8fd8\u662f\u4f7f\u7528\u5206\u53f7\uff0c\u5fd8\u4e86\u5199\u4e5f\u6ca1\u4e8b\uff0c\u5927\u90e8\u5206\u60c5\u51b5\u4e0bJavaScript\u89e3\u91ca\u5668\u90fd\u4f1a\u81ea\u52a8\u6dfb\u52a0\u3002\u5bf9\u4e8e\u4e3a\u4f55\u8981\u4f7f\u7528\u5206\u53f7\uff0c\u53ef\u53c2\u8003\u6587\u7ae0JavaScript\u4e2d\u5173\u4e8e\u5206\u53f7\u7684\u771f\u76f8\u3002<\/p>\n<h3 id=\"5\u3001\u4f7f\u7528\u5bf9\u8c61\u6784\u9020\u5668\">5\u3001\u4f7f\u7528\u5bf9\u8c61\u6784\u9020\u5668<\/h3>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<div class=\"line\">4<\/div>\n<div class=\"line\">5<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"function\"><span class=\"keyword\">function<\/span> <span class=\"title\">Person<\/span><span class=\"params\">(firstName, lastName)<\/span><\/span>{<\/div>\n<div class=\"line\"><span class=\"keyword\">this<\/span>.firstName = firstName;<\/div>\n<div class=\"line\"><span class=\"keyword\">this<\/span>.lastName = lastName;<\/div>\n<div class=\"line\">}<\/div>\n<div class=\"line\"><span class=\"keyword\">var<\/span> Saad = <span class=\"keyword\">new<\/span> Person(<span class=\"string\">\u201cSaad\u201d<\/span>, <span class=\"string\">\u201cMousliki\u201d<\/span>);<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"6\u3001\u4f7f\u7528typeof\u3001instanceof\u548ccontructor\">6\u3001\u4f7f\u7528<code>typeof<\/code>\u3001<code>instanceof<\/code>\u548c<code>contructor<\/code><\/h3>\n<ul>\n<li><code>typeof<\/code>\uff1aJavaScript\u4e00\u5143\u64cd\u4f5c\u7b26\uff0c\u7528\u4e8e\u4ee5\u5b57\u7b26\u4e32\u7684\u5f62\u5f0f\u8fd4\u56de\u53d8\u91cf\u7684\u539f\u59cb\u7c7b\u578b\uff0c\u6ce8\u610f\uff0c<code>typeof null<\/code>\u4e5f\u4f1a\u8fd4\u56de<code>object<\/code>\uff0c\u5927\u591a\u6570\u7684\u5bf9\u8c61\u7c7b\u578b\uff08\u6570\u7ec4Array\u3001\u65f6\u95f4Date\u7b49\uff09\u4e5f\u4f1a\u8fd4\u56de<code>object<\/code><\/li>\n<li><code>instanceof<\/code>\uff1a\u5185\u90e8\u539f\u578b\u5c5e\u6027\uff0c\u53ef\u4ee5\u901a\u8fc7\u4ee3\u7801\u91cd\u5199<\/li>\n<li><code>contructor<\/code>\uff1aJavaScript\u64cd\u4f5c\u7b26\uff0c\u4f1a\u5728\u539f\u578b\u94fe\u4e2d\u7684\u6784\u9020\u5668\u4e2d\u641c\u7d22\uff0c\u627e\u5230\u5219\u8fd4\u56de<code>true<\/code>\uff0c\u5426\u5219\u8fd4\u56de<code>false<\/code><\/li>\n<\/ul>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<div class=\"line\">4<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> arr = [<span class=\"string\">\u201ca\u201d<\/span>, <span class=\"string\">\u201cb\u201d<\/span>, <span class=\"string\">\u201cc\u201d<\/span>];<\/div>\n<div class=\"line\"><span class=\"keyword\">typeof<\/span> arr; <span class=\"comment\">\/\/ \u8fd4\u56de \u201cobject\u201d <\/span><\/div>\n<div class=\"line\">arr <span class=\"keyword\">instanceof<\/span> <span class=\"built_in\">Array<\/span> <span class=\"comment\">\/\/ true<\/span><\/div>\n<div class=\"line\">arr.constructor(); <span class=\"comment\">\/\/[]<\/span><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>`<\/p>\n<h3 id=\"7\u3001\u4f7f\u7528\u81ea\u8c03\u7528\u51fd\u6570\">7\u3001\u4f7f\u7528\u81ea\u8c03\u7528\u51fd\u6570<\/h3>\n<p>\u51fd\u6570\u5728\u521b\u5efa\u4e4b\u540e\u76f4\u63a5\u81ea\u52a8\u6267\u884c\uff0c\u901a\u5e38\u79f0\u4e4b\u4e3a\u81ea\u8c03\u7528\u533f\u540d\u51fd\u6570\uff08Self-Invoked Anonymous Function\uff09\u6216\u76f4\u63a5\u8c03\u7528\u51fd\u6570\u8868\u8fbe\u5f0f\uff08Immediately Invoked Function Expression \uff09\u3002\u683c\u5f0f\u5982\u4e0b\uff1a<\/p>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<div class=\"line\">4<\/div>\n<div class=\"line\">5<\/div>\n<div class=\"line\">6<\/div>\n<div class=\"line\">7<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\">(<span class=\"function\"><span class=\"keyword\">function<\/span><span class=\"params\">()<\/span><\/span>{<\/div>\n<div class=\"line\"><span class=\"comment\">\/\/ \u7f6e\u4e8e\u6b64\u5904\u7684\u4ee3\u7801\u5c06\u81ea\u52a8\u6267\u884c<\/span><\/div>\n<div class=\"line\">})();<\/div>\n<div class=\"line\">(<span class=\"function\"><span class=\"keyword\">function<\/span><span class=\"params\">(a,b)<\/span><\/span>{<\/div>\n<div class=\"line\"><span class=\"keyword\">var<\/span> result = a+b;<\/div>\n<div class=\"line\"><span class=\"keyword\">return<\/span> result;<\/div>\n<div class=\"line\">})(<span class=\"number\">10<\/span>,<span class=\"number\">20<\/span>)<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"8\u3001\u4ece\u6570\u7ec4\u4e2d\u968f\u673a\u83b7\u53d6\u6210\u5458\">8\u3001\u4ece\u6570\u7ec4\u4e2d\u968f\u673a\u83b7\u53d6\u6210\u5458<\/h3>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> items = [<span class=\"number\">12<\/span>, <span class=\"number\">548<\/span> , <span class=\"string\">\u2018a\u2019<\/span> , <span class=\"number\">2<\/span> , <span class=\"number\">5478<\/span> , <span class=\"string\">\u2018foo\u2019<\/span> , <span class=\"number\">8852<\/span>, , <span class=\"string\">\u2018Doe\u2019<\/span> , <span class=\"number\">2145<\/span> , <span class=\"number\">119<\/span>];<\/div>\n<div class=\"line\"><span class=\"keyword\">var<\/span> randomItem = items[<span class=\"built_in\">Math<\/span>.floor(<span class=\"built_in\">Math<\/span>.random() * items.length)];<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"9\u3001\u83b7\u53d6\u6307\u5b9a\u8303\u56f4\u5185\u7684\u968f\u673a\u6570\">9\u3001\u83b7\u53d6\u6307\u5b9a\u8303\u56f4\u5185\u7684\u968f\u673a\u6570<\/h3>\n<p>\u8fd9\u4e2a\u529f\u80fd\u5728\u751f\u6210\u6d4b\u8bd5\u7528\u7684\u5047\u6570\u636e\u65f6\u7279\u522b\u6709\u6570\uff0c\u6bd4\u5982\u4ecb\u4e0e\u6307\u5b9a\u8303\u56f4\u5185\u7684\u5de5\u8d44\u6570\u3002<\/p>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> x = <span class=\"built_in\">Math<\/span>.floor(<span class=\"built_in\">Math<\/span>.random() * (max \u2013 min + <span class=\"number\">1<\/span>)) + min;<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"10\u3001\u751f\u6210\u4ece0\u5230\u6307\u5b9a\u503c\u7684\u6570\u5b57\u6570\u7ec4\">10\u3001\u751f\u6210\u4ece0\u5230\u6307\u5b9a\u503c\u7684\u6570\u5b57\u6570\u7ec4<\/h3>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> numbersArray = [] , max = <span class=\"number\">100<\/span>;<\/div>\n<div class=\"line\"><span class=\"keyword\">for<\/span>( <span class=\"keyword\">var<\/span> i=<span class=\"number\">1<\/span>; numbersArray.push(i++) &lt; max;); <span class=\"comment\">\/\/ numbers = [1,2,3 \u2026 100]<\/span><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"11\u3001\u751f\u6210\u968f\u673a\u7684\u5b57\u6bcd\u6570\u5b57\u5b57\u7b26\u4e32\">11\u3001\u751f\u6210\u968f\u673a\u7684\u5b57\u6bcd\u6570\u5b57\u5b57\u7b26\u4e32<\/h3>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<div class=\"line\">4<\/div>\n<div class=\"line\">5<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"function\"><span class=\"keyword\">function<\/span> <span class=\"title\">generateRandomAlphaNum<\/span><span class=\"params\">(len)<\/span> <\/span>{<\/div>\n<div class=\"line\"><span class=\"keyword\">var<\/span> rdmString = <span class=\"string\">\u201c\u201d<\/span>;<\/div>\n<div class=\"line\"><span class=\"keyword\">for<\/span>( ; rdmString.length &lt; len; rdmString += <span class=\"built_in\">Math<\/span>.random().toString(<span class=\"number\">36<\/span>).substr(<span class=\"number\">2<\/span>));<\/div>\n<div class=\"line\"><span class=\"keyword\">return<\/span> rdmString.substr(<span class=\"number\">0<\/span>, len);<\/div>\n<div class=\"line\">}<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"12\u3001\u6253\u4e71\u6570\u5b57\u6570\u7ec4\u7684\u987a\u5e8f\">12\u3001\u6253\u4e71\u6570\u5b57\u6570\u7ec4\u7684\u987a\u5e8f<\/h3>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> numbers = [<span class=\"number\">5<\/span>, <span class=\"number\">458<\/span> , <span class=\"number\">120<\/span> , &#8211;<span class=\"number\">215<\/span> , <span class=\"number\">228<\/span> , <span class=\"number\">400<\/span> , <span class=\"number\">122205<\/span>, &#8211;<span class=\"number\">85411<\/span>];<\/div>\n<div class=\"line\">numbers = numbers.sort(<span class=\"function\"><span class=\"keyword\">function<\/span><span class=\"params\">()<\/span><\/span>{ <span class=\"keyword\">return<\/span> <span class=\"built_in\">Math<\/span>.random() \u2013 <span class=\"number\">0.5<\/span>});<\/div>\n<div class=\"line\"><span class=\"comment\">\/* numbers \u6570\u7ec4\u5c06\u7c7b\u4f3c\u4e8e [120, 5, 228, -215, 400, 458, -85411, 122205] *\/<\/span><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>\u8fd9\u91cc\u4f7f\u7528\u4e86JavaScript\u5185\u7f6e\u7684\u6570\u7ec4\u6392\u5e8f\u51fd\u6570\uff0c\u66f4\u597d\u7684\u529e\u6cd5\u662f\u7528\u4e13\u95e8\u7684\u4ee3\u7801\u6765\u5b9e\u73b0\uff08\u5982Fisher-Yates\u7b97\u6cd5\uff09\uff0c\u53ef\u4ee5\u53c2\u89c1StackOverFlow\u4e0a\u7684\u8fd9\u4e2a\u8ba8\u8bba\u3002<\/p>\n<h3 id=\"13\u3001\u5b57\u7b26\u4e32\u53bb\u7a7a\u683c\">13\u3001\u5b57\u7b26\u4e32\u53bb\u7a7a\u683c<\/h3>\n<p>Java\u3001C#\u548cPHP\u7b49\u8bed\u8a00\u90fd\u5b9e\u73b0\u4e86\u4e13\u95e8\u7684\u5b57\u7b26\u4e32\u53bb\u7a7a\u683c\u51fd\u6570\uff0c\u4f46JavaScript\u4e2d\u662f\u6ca1\u6709\u7684\uff0c\u53ef\u4ee5\u901a\u8fc7\u4e0b\u9762\u7684\u4ee3\u7801\u6765\u4e3a<code>String<\/code>\u5bf9\u8c61\u51fd\u6570\u4e00\u4e2a<code>trim<\/code>\u51fd\u6570\uff1a<\/p>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"built_in\">String<\/span>.prototype.trim = <span class=\"function\"><span class=\"keyword\">function<\/span><span class=\"params\">()<\/span><\/span>{<span class=\"keyword\">return<\/span> <span class=\"keyword\">this<\/span>.replace(<span class=\"regexp\">\/^\\s+|\\s+$\/g<\/span>, <span class=\"string\">\u201c\u201d<\/span>);};<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>\u65b0\u7684JavaScript\u5f15\u64ce\u5df2\u7ecf\u6709\u4e86<code>trim()<\/code>\u7684\u539f\u751f\u5b9e\u73b0\u3002<\/p>\n<h3 id=\"14\u3001\u6570\u7ec4\u4e4b\u95f4\u8ffd\u52a0\">14\u3001\u6570\u7ec4\u4e4b\u95f4\u8ffd\u52a0<\/h3>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<div class=\"line\">4<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> array1 = [<span class=\"number\">12<\/span> , <span class=\"string\">\u201cfoo\u201d<\/span> , {name <span class=\"string\">\u201cJoe\u201d<\/span>} , &#8211;<span class=\"number\">2458<\/span>];<\/div>\n<div class=\"line\"><span class=\"keyword\">var<\/span> array2 = [<span class=\"string\">\u201cDoe\u201d<\/span> , <span class=\"number\">555<\/span> , <span class=\"number\">100<\/span>];<\/div>\n<div class=\"line\"><span class=\"built_in\">Array<\/span>.prototype.push.apply(array1, array2);<\/div>\n<div class=\"line\"><span class=\"comment\">\/* array1 \u503c\u4e3a [12 , \u201cfoo\u201d , {name \u201cJoe\u201d} , -2458 , \u201cDoe\u201d , 555 , 100] *\/<\/span><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"15\u3001\u5bf9\u8c61\u8f6c\u6362\u4e3a\u6570\u7ec4\">15\u3001\u5bf9\u8c61\u8f6c\u6362\u4e3a\u6570\u7ec4<\/h3>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> argArray = <span class=\"built_in\">Array<\/span>.prototype.slice.call(<span class=\"built_in\">arguments<\/span>);<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"16\u3001\u9a8c\u8bc1\u662f\u5426\u662f\u6570\u5b57\">16\u3001\u9a8c\u8bc1\u662f\u5426\u662f\u6570\u5b57<\/h3>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"function\"><span class=\"keyword\">function<\/span> <span class=\"title\">isNumber<\/span><span class=\"params\">(n)<\/span><\/span>{<\/div>\n<div class=\"line\"><span class=\"keyword\">return<\/span> !<span class=\"built_in\">isNaN<\/span>(<span class=\"built_in\">parseFloat<\/span>(n)) &amp;&amp; <span class=\"built_in\">isFinite<\/span>(n);<\/div>\n<div class=\"line\">}<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"17\u3001\u9a8c\u8bc1\u662f\u5426\u662f\u6570\u7ec4\">17\u3001\u9a8c\u8bc1\u662f\u5426\u662f\u6570\u7ec4<\/h3>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"function\"><span class=\"keyword\">function<\/span> <span class=\"title\">isArray<\/span><span class=\"params\">(obj)<\/span><\/span>{<\/div>\n<div class=\"line\"><span class=\"keyword\">return<\/span> <span class=\"built_in\">Object<\/span>.prototype.toString.call(obj) === <span class=\"string\">\u2018[object Array]\u2019<\/span> ;<\/div>\n<div class=\"line\">}<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>\u4f46\u5982\u679c<code>toString()<\/code>\u65b9\u6cd5\u88ab\u91cd\u5199\u8fc7\u5f97\u8bdd\uff0c\u5c31\u884c\u4e0d\u901a\u4e86\u3002\u4e5f\u53ef\u4ee5\u4f7f\u7528\u4e0b\u9762\u7684\u65b9\u6cd5\uff1a<\/p>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"built_in\">Array<\/span>.isArray(obj); <span class=\"comment\">\/\/ its a new Array method<\/span><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>`<\/p>\n<p>\u5982\u679c\u5728\u6d4f\u89c8\u5668\u4e2d\u6ca1\u6709\u4f7f\u7528frame\uff0c\u8fd8\u53ef\u4ee5\u7528<code>instanceof<\/code>\uff0c\u4f46\u5982\u679c\u4e0a\u4e0b\u6587\u592a\u590d\u6742\uff0c\u4e5f\u6709\u53ef\u80fd\u51fa\u9519\u3002<\/p>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<div class=\"line\">4<\/div>\n<div class=\"line\">5<\/div>\n<div class=\"line\">6<\/div>\n<div class=\"line\">7<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> myFrame = <span class=\"built_in\">document<\/span>.createElement(<span class=\"string\">\u2018iframe\u2019<\/span>);<\/div>\n<div class=\"line\"><span class=\"built_in\">document<\/span>.body.appendChild(myFrame);<\/div>\n<div class=\"line\"><span class=\"keyword\">var<\/span> myArray = <span class=\"built_in\">window<\/span>.frames[<span class=\"built_in\">window<\/span>.frames.length-<span class=\"number\">1<\/span>].Array;<\/div>\n<div class=\"line\"><span class=\"keyword\">var<\/span> arr = <span class=\"keyword\">new<\/span> myArray(a,b,<span class=\"number\">10<\/span>); <span class=\"comment\">\/\/ [a,b,10] <\/span><\/div>\n<div class=\"line\"><span class=\"comment\">\/\/ myArray \u7684\u6784\u9020\u5668\u5df2\u7ecf\u4e22\u5931\uff0cinstanceof \u7684\u7ed3\u679c\u5c06\u4e0d\u6b63\u5e38<\/span><\/div>\n<div class=\"line\"><span class=\"comment\">\/\/ \u6784\u9020\u5668\u662f\u4e0d\u80fd\u8de8 frame \u5171\u4eab\u7684<\/span><\/div>\n<div class=\"line\">arr <span class=\"keyword\">instanceof<\/span> <span class=\"built_in\">Array<\/span>; <span class=\"comment\">\/\/ false<\/span><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"18\u3001\u83b7\u53d6\u6570\u7ec4\u4e2d\u7684\u6700\u5927\u503c\u548c\u6700\u5c0f\u503c\">18\u3001\u83b7\u53d6\u6570\u7ec4\u4e2d\u7684\u6700\u5927\u503c\u548c\u6700\u5c0f\u503c<\/h3>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> numbers = [<span class=\"number\">5<\/span>, <span class=\"number\">458<\/span> , <span class=\"number\">120<\/span> , &#8211;<span class=\"number\">215<\/span> , <span class=\"number\">228<\/span> , <span class=\"number\">400<\/span> , <span class=\"number\">122205<\/span>, &#8211;<span class=\"number\">85411<\/span>];<\/div>\n<div class=\"line\"><span class=\"keyword\">var<\/span> maxInNumbers = <span class=\"built_in\">Math<\/span>.max.apply(<span class=\"built_in\">Math<\/span>, numbers);<\/div>\n<div class=\"line\"><span class=\"keyword\">var<\/span> minInNumbers = <span class=\"built_in\">Math<\/span>.min.apply(<span class=\"built_in\">Math<\/span>, numbers);<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"19\u3001\u6e05\u7a7a\u6570\u7ec4\">19\u3001\u6e05\u7a7a\u6570\u7ec4<\/h3>\n<figure class=\"highlight\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> myArray = [<span class=\"number\">12<\/span> , <span class=\"number\">222<\/span> , <span class=\"number\">1000<\/span> ];<\/div>\n<div class=\"line\">myArray.length = <span class=\"number\">0<\/span>; <span class=\"comment\">\/\/ myArray will be equal to [].<\/span><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"20\u3001\u4e0d\u8981\u76f4\u63a5\u4ece\u6570\u7ec4\u4e2ddelete\u6216remove\u5143\u7d20\">20\u3001\u4e0d\u8981\u76f4\u63a5\u4ece\u6570\u7ec4\u4e2d<code>delete<\/code>\u6216<code>remove<\/code>\u5143\u7d20<\/h3>\n<p>\u5982\u679c\u5bf9\u6570\u7ec4\u5143\u7d20\u76f4\u63a5\u4f7f\u7528<code>delete<\/code>\uff0c\u5176\u5b9e\u5e76\u6ca1\u6709\u5220\u9664\uff0c\u53ea\u662f\u5c06\u5143\u7d20\u7f6e\u4e3a\u4e86<code>undefined<\/code>\u3002\u6570\u7ec4\u5143\u7d20\u5220\u9664\u5e94\u4f7f\u7528<code>splice<\/code>\u3002<\/p>\n<p>\u5207\u5fcc\uff1a<\/p>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<div class=\"line\">4<\/div>\n<div class=\"line\">5<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> items = [<span class=\"number\">12<\/span>, <span class=\"number\">548<\/span> ,<span class=\"string\">\u2018a\u2019<\/span> , <span class=\"number\">2<\/span> , <span class=\"number\">5478<\/span> , <span class=\"string\">\u2018foo\u2019<\/span> , <span class=\"number\">8852<\/span>, , <span class=\"string\">\u2018Doe\u2019<\/span> ,<span class=\"number\">2154<\/span> , <span class=\"number\">119<\/span> ];<\/div>\n<div class=\"line\">items.length; <span class=\"comment\">\/\/ return 11 <\/span><\/div>\n<div class=\"line\"><span class=\"keyword\">delete<\/span> items[<span class=\"number\">3<\/span>]; <span class=\"comment\">\/\/ return true <\/span><\/div>\n<div class=\"line\">items.length; <span class=\"comment\">\/\/ return 11 <\/span><\/div>\n<div class=\"line\"><span class=\"comment\">\/* items \u7ed3\u679c\u4e3a [12, 548, \u201ca\u201d, undefined \u00d7 1, 5478, \u201cfoo\u201d, 8852, undefined \u00d7 1, \u201cDoe\u201d, 2154, 119] *\/<\/span><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>\u800c\u5e94\uff1a<\/p>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<div class=\"line\">4<\/div>\n<div class=\"line\">5<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> items = [<span class=\"number\">12<\/span>, <span class=\"number\">548<\/span> ,<span class=\"string\">\u2018a\u2019<\/span> , <span class=\"number\">2<\/span> , <span class=\"number\">5478<\/span> , <span class=\"string\">\u2018foo\u2019<\/span> , <span class=\"number\">8852<\/span>, , <span class=\"string\">\u2018Doe\u2019<\/span> ,<span class=\"number\">2154<\/span> , <span class=\"number\">119<\/span> ];<\/div>\n<div class=\"line\">items.length; <span class=\"comment\">\/\/ return 11 <\/span><\/div>\n<div class=\"line\">items.splice(<span class=\"number\">3<\/span>,<span class=\"number\">1<\/span>) ;<\/div>\n<div class=\"line\">items.length; <span class=\"comment\">\/\/ return 10 <\/span><\/div>\n<div class=\"line\"><span class=\"comment\">\/* items \u7ed3\u679c\u4e3a [12, 548, \u201ca\u201d, 5478, \u201cfoo\u201d, 8852, undefined \u00d7 1, \u201cDoe\u201d, 2154, 119]<\/span><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>\u5220\u9664\u5bf9\u8c61\u7684\u5c5e\u6027\u65f6\u53ef\u4ee5\u4f7f\u7528<code>delete<\/code>\u3002<\/p>\n<h3 id=\"21\u3001\u4f7f\u7528length\u5c5e\u6027\u622a\u65ad\u6570\u7ec4\">21\u3001\u4f7f\u7528<code>length<\/code>\u5c5e\u6027\u622a\u65ad\u6570\u7ec4<\/h3>\n<p>\u524d\u9762\u7684\u4f8b\u5b50\u4e2d\u7528<code>length<\/code>\u5c5e\u6027\u6e05\u7a7a\u6570\u7ec4\uff0c\u540c\u6837\u8fd8\u53ef\u7528\u5b83\u6765\u622a\u65ad\u6570\u7ec4\uff1a<\/p>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> myArray = [<span class=\"number\">12<\/span> , <span class=\"number\">222<\/span> , <span class=\"number\">1000<\/span> , <span class=\"number\">124<\/span> , <span class=\"number\">98<\/span> , <span class=\"number\">10<\/span> ];<\/div>\n<div class=\"line\">myArray.length = <span class=\"number\">4<\/span>; <span class=\"comment\">\/\/ myArray will be equal to [12 , 222 , 1000 , 124].<\/span><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>\u4e0e\u6b64\u540c\u65f6\uff0c\u5982\u679c\u628a<code>length<\/code>\u5c5e\u6027\u53d8\u5927\uff0c\u6570\u7ec4\u7684\u957f\u5ea6\u503c\u53d8\u4f1a\u589e\u52a0\uff0c\u4f1a\u4f7f\u7528<code>undefined<\/code>\u6765\u4f5c\u4e3a\u65b0\u7684\u5143\u7d20\u586b\u5145\u3002<code>length<\/code>\u662f\u4e00\u4e2a\u53ef\u5199\u7684\u5c5e\u6027\u3002<\/p>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\">myArray.length = <span class=\"number\">10<\/span>; <span class=\"comment\">\/\/ the new array length is 10 <\/span><\/div>\n<div class=\"line\">myArray[myArray.length \u2013 <span class=\"number\">1<\/span>] ; <span class=\"comment\">\/\/ undefined<\/span><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"22\u3001\u5728\u6761\u4ef6\u4e2d\u4f7f\u7528\u903b\u8f91\u4e0e\u6216\">22\u3001\u5728\u6761\u4ef6\u4e2d\u4f7f\u7528\u903b\u8f91\u4e0e\u6216<\/h3>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> foo = <span class=\"number\">10<\/span>;<\/div>\n<div class=\"line\">foo == <span class=\"number\">10<\/span> &amp;&amp; doSomething(); <span class=\"comment\">\/\/ is the same thing as if (foo == 10) doSomething(); <\/span><\/div>\n<div class=\"line\">foo == <span class=\"number\">5<\/span> || doSomething(); <span class=\"comment\">\/\/ is the same thing as if (foo != 5) doSomething();<\/span><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>\u903b\u8f91\u6216\u8fd8\u53ef\u7528\u6765\u8bbe\u7f6e\u9ed8\u8ba4\u503c\uff0c\u6bd4\u5982\u51fd\u6570\u53c2\u6570\u7684\u9ed8\u8ba4\u503c\u3002<\/p>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"function\"><span class=\"keyword\">function<\/span> <span class=\"title\">doSomething<\/span><span class=\"params\">(arg1)<\/span><\/span>{<\/div>\n<div class=\"line\">arg1 = arg1 || <span class=\"number\">10<\/span>; <span class=\"comment\">\/\/ arg1 will have 10 as a default value if it\u2019s not already set<\/span><\/div>\n<div class=\"line\">}<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"23\u3001\u4f7f\u5f97map()\u51fd\u6570\u65b9\u6cd5\u5bf9\u6570\u636e\u5faa\u73af\">23\u3001\u4f7f\u5f97<code>map()<\/code>\u51fd\u6570\u65b9\u6cd5\u5bf9\u6570\u636e\u5faa\u73af<\/h3>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<div class=\"line\">4<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> squares = [<span class=\"number\">1<\/span>,<span class=\"number\">2<\/span>,<span class=\"number\">3<\/span>,<span class=\"number\">4<\/span>].map(<span class=\"function\"><span class=\"keyword\">function<\/span> <span class=\"params\">(val)<\/span> <\/span>{<\/div>\n<div class=\"line\"><span class=\"keyword\">return<\/span> val * val;<\/div>\n<div class=\"line\">});<\/div>\n<div class=\"line\"><span class=\"comment\">\/\/ squares will be equal to [1, 4, 9, 16]<\/span><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"24\u3001\u4fdd\u7559\u6307\u5b9a\u5c0f\u6570\u4f4d\u6570\">24\u3001\u4fdd\u7559\u6307\u5b9a\u5c0f\u6570\u4f4d\u6570<\/h3>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> num =<span class=\"number\">2.443242342<\/span>;<\/div>\n<div class=\"line\">num = num.toFixed(<span class=\"number\">4<\/span>); <span class=\"comment\">\/\/ num will be equal to 2.4432<\/span><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>\u6ce8\u610f\uff0c<code>toFixec()<\/code>\u8fd4\u56de\u7684\u662f\u5b57\u7b26\u4e32\uff0c\u4e0d\u662f\u6570\u5b57\u3002<\/p>\n<h3 id=\"25\u3001\u6d6e\u70b9\u8ba1\u7b97\u7684\u95ee\u9898\">25\u3001\u6d6e\u70b9\u8ba1\u7b97\u7684\u95ee\u9898<\/h3>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"number\">0.1<\/span> + <span class=\"number\">0.2<\/span> === <span class=\"number\">0.3<\/span> <span class=\"comment\">\/\/ is false <\/span><\/div>\n<div class=\"line\"><span class=\"number\">9007199254740992<\/span> + <span class=\"number\">1<\/span> <span class=\"comment\">\/\/ is equal to 9007199254740992<\/span><\/div>\n<div class=\"line\"><span class=\"number\">9007199254740992<\/span> + <span class=\"number\">2<\/span> <span class=\"comment\">\/\/ is equal to 9007199254740994<\/span><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>\u4e3a\u4ec0\u4e48\u5462\uff1f\u56e0\u4e3a0.1+0.2\u7b49\u4e8e0.30000000000000004\u3002JavaScript\u7684\u6570\u5b57\u90fd\u9075\u5faaIEEE 754\u6807\u51c6\u6784\u5efa\uff0c\u5728\u5185\u90e8\u90fd\u662f64\u4f4d\u6d6e\u70b9\u5c0f\u6570\u8868\u793a\uff0c\u5177\u4f53\u53ef\u4ee5\u53c2\u89c1JavaScript\u4e2d\u7684\u6570\u5b57\u662f\u5982\u4f55\u7f16\u7801\u7684.<\/p>\n<p>\u53ef\u4ee5\u901a\u8fc7\u4f7f\u7528<code>toFixed()<\/code>\u548c<code>toPrecision()<\/code>\u6765\u89e3\u51b3\u8fd9\u4e2a\u95ee\u9898\u3002<\/p>\n<h3 id=\"26\u3001\u901a\u8fc7for-in\u5faa\u73af\u68c0\u67e5\u5bf9\u8c61\u7684\u5c5e\u6027\">26\u3001\u901a\u8fc7for-in\u5faa\u73af\u68c0\u67e5\u5bf9\u8c61\u7684\u5c5e\u6027<\/h3>\n<p>\u4e0b\u9762\u8fd9\u6837\u7684\u7528\u6cd5\uff0c\u53ef\u4ee5\u9632\u6b62\u8fed\u4ee3\u7684\u65f6\u5019\u8fdb\u5165\u5230\u5bf9\u8c61\u7684\u539f\u578b\u5c5e\u6027\u4e2d\u3002<\/p>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<div class=\"line\">4<\/div>\n<div class=\"line\">5<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">for<\/span> (<span class=\"keyword\">var<\/span> name <span class=\"keyword\">in<\/span> object) {<\/div>\n<div class=\"line\"><span class=\"keyword\">if<\/span> (object.hasOwnProperty(name)) {<\/div>\n<div class=\"line\"><span class=\"comment\">\/\/ do something with name<\/span><\/div>\n<div class=\"line\">}<\/div>\n<div class=\"line\">}<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"27\u3001\u9017\u53f7\u64cd\u4f5c\u7b26\">27\u3001\u9017\u53f7\u64cd\u4f5c\u7b26<\/h3>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<div class=\"line\">4<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> a = <span class=\"number\">0<\/span>;<\/div>\n<div class=\"line\"><span class=\"keyword\">var<\/span> b = ( a++, <span class=\"number\">99<\/span> );<\/div>\n<div class=\"line\"><span class=\"built_in\">console<\/span>.log(a); <span class=\"comment\">\/\/ a will be equal to 1 <\/span><\/div>\n<div class=\"line\"><span class=\"built_in\">console<\/span>.log(b); <span class=\"comment\">\/\/ b is equal to 99<\/span><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"28\u3001\u4e34\u65f6\u5b58\u50a8\u7528\u4e8e\u8ba1\u7b97\u548c\u67e5\u8be2\u7684\u53d8\u91cf\">28\u3001\u4e34\u65f6\u5b58\u50a8\u7528\u4e8e\u8ba1\u7b97\u548c\u67e5\u8be2\u7684\u53d8\u91cf<\/h3>\n<p>\u5728jQuery\u9009\u62e9\u5668\u4e2d\uff0c\u53ef\u4ee5\u4e34\u65f6\u5b58\u50a8\u6574\u4e2aDOM\u5143\u7d20\u3002<\/p>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<div class=\"line\">4<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> navright = <span class=\"built_in\">document<\/span>.querySelector(<span class=\"string\">\u2018#right\u2019<\/span>);<\/div>\n<div class=\"line\"><span class=\"keyword\">var<\/span> navleft = <span class=\"built_in\">document<\/span>.querySelector(<span class=\"string\">\u2018#left\u2019<\/span>);<\/div>\n<div class=\"line\"><span class=\"keyword\">var<\/span> navup = <span class=\"built_in\">document<\/span>.querySelector(<span class=\"string\">\u2018#up\u2019<\/span>);<\/div>\n<div class=\"line\"><span class=\"keyword\">var<\/span> navdown = <span class=\"built_in\">document<\/span>.querySelector(<span class=\"string\">\u2018#down\u2019<\/span>);<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"29\u3001\u63d0\u524d\u68c0\u67e5\u4f20\u5165isFinite()\u7684\u53c2\u6570\">29\u3001\u63d0\u524d\u68c0\u67e5\u4f20\u5165<code>isFinite()<\/code>\u7684\u53c2\u6570<\/h3>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<div class=\"line\">4<\/div>\n<div class=\"line\">5<\/div>\n<div class=\"line\">6<\/div>\n<div class=\"line\">7<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"built_in\">isFinite<\/span>(<span class=\"number\">0<\/span>\/<span class=\"number\">0<\/span>) ; <span class=\"comment\">\/\/ false<\/span><\/div>\n<div class=\"line\"><span class=\"built_in\">isFinite<\/span>(<span class=\"string\">\u201cfoo\u201d<\/span>); <span class=\"comment\">\/\/ false<\/span><\/div>\n<div class=\"line\"><span class=\"built_in\">isFinite<\/span>(<span class=\"string\">\u201c10\u201d<\/span>); <span class=\"comment\">\/\/ true<\/span><\/div>\n<div class=\"line\"><span class=\"built_in\">isFinite<\/span>(<span class=\"number\">10<\/span>); <span class=\"comment\">\/\/ true<\/span><\/div>\n<div class=\"line\"><span class=\"built_in\">isFinite<\/span>(<span class=\"literal\">undefined<\/span>); <span class=\"comment\">\/\/ false<\/span><\/div>\n<div class=\"line\"><span class=\"built_in\">isFinite<\/span>(); <span class=\"comment\">\/\/ false<\/span><\/div>\n<div class=\"line\"><span class=\"built_in\">isFinite<\/span>(<span class=\"literal\">null<\/span>); <span class=\"comment\">\/\/ true\uff0c\u8fd9\u70b9\u5f53\u7279\u522b\u6ce8\u610f<\/span><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"30\u3001\u907f\u514d\u5728\u6570\u7ec4\u4e2d\u4f7f\u7528\u8d1f\u6570\u505a\u7d22\u5f15\">30\u3001\u907f\u514d\u5728\u6570\u7ec4\u4e2d\u4f7f\u7528\u8d1f\u6570\u505a\u7d22\u5f15<\/h3>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> numbersArray = [<span class=\"number\">1<\/span>,<span class=\"number\">2<\/span>,<span class=\"number\">3<\/span>,<span class=\"number\">4<\/span>,<span class=\"number\">5<\/span>];<\/div>\n<div class=\"line\"><span class=\"keyword\">var<\/span> from = numbersArray.indexOf(<span class=\"string\">\u201cfoo\u201d<\/span>) ; <span class=\"comment\">\/\/ from is equal to -1<\/span><\/div>\n<div class=\"line\">numbersArray.splice(from,<span class=\"number\">2<\/span>); <span class=\"comment\">\/\/ will return [5]<\/span><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>\u6ce8\u610f\u4f20\u7ed9<code>splice<\/code>\u7684\u7d22\u5f15\u53c2\u6570\u4e0d\u8981\u662f\u8d1f\u6570\uff0c\u5f53\u662f\u8d1f\u6570\u65f6\uff0c\u4f1a\u4ece\u6570\u7ec4\u7ed3\u5c3e\u5904\u5220\u9664\u5143\u7d20\u3002<\/p>\n<h3 id=\"31\u3001\u7528JSON\u6765\u5e8f\u5217\u5316\u4e0e\u53cd\u5e8f\u5217\u5316\">31\u3001\u7528JSON\u6765\u5e8f\u5217\u5316\u4e0e\u53cd\u5e8f\u5217\u5316<\/h3>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<div class=\"line\">4<\/div>\n<div class=\"line\">5<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> person = {name :<span class=\"string\">\u2018Saad\u2019<\/span>, age : <span class=\"number\">26<\/span>, department : {ID : <span class=\"number\">15<\/span>, name : <span class=\"string\">\u201cR&amp;D\u201d<\/span>} };<\/div>\n<div class=\"line\"><span class=\"keyword\">var<\/span> stringFromPerson = <span class=\"built_in\">JSON<\/span>.stringify(person);<\/div>\n<div class=\"line\"><span class=\"comment\">\/* stringFromPerson \u7ed3\u679c\u4e3a \u201c{\u201cname\u201d:\u201dSaad\u201d,\u201dage\u201d:26,\u201ddepartment\u201d:{\u201cID\u201d:15,\u201dname\u201d:\u201dR&amp;D\u201d}}\u201d *\/<\/span><\/div>\n<div class=\"line\"><span class=\"keyword\">var<\/span> personFromString = <span class=\"built_in\">JSON<\/span>.parse(stringFromPerson);<\/div>\n<div class=\"line\"><span class=\"comment\">\/* personFromString \u7684\u503c\u4e0e person \u5bf9\u8c61\u76f8\u540c *\/<\/span><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"32\u3001\u4e0d\u8981\u4f7f\u7528eval()\u6216\u8005\u51fd\u6570\u6784\u9020\u5668\">32\u3001\u4e0d\u8981\u4f7f\u7528<code>eval()<\/code>\u6216\u8005\u51fd\u6570\u6784\u9020\u5668<\/h3>\n<p><code>eval()<\/code>\u548c\u51fd\u6570\u6784\u9020\u5668\uff08<code>Function<\/code> consturctor\uff09\u7684\u5f00\u9500\u8f83\u5927\uff0c\u6bcf\u6b21\u8c03\u7528\uff0cJavaScript\u5f15\u64ce\u90fd\u8981\u5c06\u6e90\u4ee3\u7801\u8f6c\u6362\u4e3a\u53ef\u6267\u884c\u7684\u4ee3\u7801\u3002<\/p>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> func1 = <span class=\"keyword\">new<\/span> <span class=\"built_in\">Function<\/span>(functionCode);<\/div>\n<div class=\"line\"><span class=\"keyword\">var<\/span> func2 = <span class=\"built_in\">eval<\/span>(functionCode);<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"33\u3001\u907f\u514d\u4f7f\u7528with()\">33\u3001\u907f\u514d\u4f7f\u7528<code>with()<\/code><\/h3>\n<p>\u4f7f\u7528<code>with()<\/code>\u53ef\u4ee5\u628a\u53d8\u91cf\u52a0\u5165\u5230\u5168\u5c40\u4f5c\u7528\u57df\u4e2d\uff0c\u56e0\u6b64\uff0c\u5982\u679c\u6709\u5176\u5b83\u7684\u540c\u540d\u53d8\u91cf\uff0c\u4e00\u6765\u5bb9\u6613\u6df7\u6dc6\uff0c\u4e8c\u6765\u503c\u4e5f\u4f1a\u88ab\u8986\u76d6\u3002<\/p>\n<h3 id=\"34\u3001\u4e0d\u8981\u5bf9\u6570\u7ec4\u4f7f\u7528for-in\">34\u3001\u4e0d\u8981\u5bf9\u6570\u7ec4\u4f7f\u7528for-in<\/h3>\n<p>\u907f\u514d\uff1a<\/p>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<div class=\"line\">4<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> sum = <span class=\"number\">0<\/span>;<\/div>\n<div class=\"line\"><span class=\"keyword\">for<\/span> (<span class=\"keyword\">var<\/span> i <span class=\"keyword\">in<\/span> arrayNumbers) {<\/div>\n<div class=\"line\">sum += arrayNumbers[i];<\/div>\n<div class=\"line\">}<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>\u800c\u662f\uff1a<\/p>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<div class=\"line\">4<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> sum = <span class=\"number\">0<\/span>;<\/div>\n<div class=\"line\"><span class=\"keyword\">for<\/span> (<span class=\"keyword\">var<\/span> i = <span class=\"number\">0<\/span>, len = arrayNumbers.length; i &lt; len; i++) {<\/div>\n<div class=\"line\">sum += arrayNumbers[i];<\/div>\n<div class=\"line\">}<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>\u53e6\u5916\u4e00\u4e2a\u597d\u5904\u662f\uff0c<code>i<\/code>\u548c<code>len<\/code>\u4e24\u4e2a\u53d8\u91cf\u662f\u5728<code>for<\/code>\u5faa\u73af\u7684\u7b2c\u4e00\u4e2a\u58f0\u660e\u4e2d\uff0c\u4e8c\u8005\u53ea\u4f1a\u521d\u59cb\u5316\u4e00\u6b21\uff0c\u8fd9\u8981\u6bd4\u4e0b\u9762\u8fd9\u79cd\u5199\u6cd5\u5feb\uff1a<\/p>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">for<\/span> (<span class=\"keyword\">var<\/span> i = <span class=\"number\">0<\/span>; i &lt; arrayNumbers.length; i++)<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"35\u3001\u4f20\u7ed9setInterval()\u548csetTimeout()\u65f6\u4f7f\u7528\u51fd\u6570\u800c\u4e0d\u662f\u5b57\u7b26\u4e32\">35\u3001\u4f20\u7ed9<code>setInterval()<\/code>\u548c<code>setTimeout()<\/code>\u65f6\u4f7f\u7528\u51fd\u6570\u800c\u4e0d\u662f\u5b57\u7b26\u4e32<\/h3>\n<p>\u5982\u679c\u4f20\u7ed9<code>setTimeout()<\/code>\u548c<code>setInterval()<\/code>\u4e00\u4e2a\u5b57\u7b26\u4e32\uff0c\u4ed6\u4eec\u5c06\u4f1a\u7528\u7c7b\u4f3c\u4e8e<code>eval<\/code>\u65b9\u5f0f\u8fdb\u884c\u8f6c\u6362\uff0c\u8fd9\u80af\u5b9a\u4f1a\u8981\u6162\u4e9b\uff0c\u56e0\u6b64\u4e0d\u8981\u4f7f\u7528\uff1a<\/p>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\">setInterval(<span class=\"string\">\u2018doSomethingPeriodically()\u2019<\/span>, <span class=\"number\">1000<\/span>);<\/div>\n<div class=\"line\">setTimeout(<span class=\"string\">\u2018doSomethingAfterFiveSeconds()\u2019<\/span>, <span class=\"number\">5000<\/span>);<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>\u800c\u662f\u7528\uff1a<\/p>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\">setInterval(doSomethingPeriodically, <span class=\"number\">1000<\/span>);<\/div>\n<div class=\"line\">setTimeout(doSomethingAfterFiveSeconds, <span class=\"number\">5000<\/span>);<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"36\u3001\u4f7f\u7528switch\/case\u4ee3\u66ff\u4e00\u5927\u53e0\u7684if\/else\">36\u3001\u4f7f\u7528<code>switch\/case<\/code>\u4ee3\u66ff\u4e00\u5927\u53e0\u7684<code>if\/else<\/code><\/h3>\n<p>\u5f53\u5224\u65ad\u6709\u8d85\u8fc7\u4e24\u4e2a\u5206\u652f\u7684\u65f6\u5019\u4f7f\u7528<code>switch\/case<\/code>\u8981\u66f4\u5feb\u4e00\u4e9b\uff0c\u800c\u4e14\u4e5f\u66f4\u4f18\u96c5\uff0c\u66f4\u5229\u4e8e\u4ee3\u7801\u7684\u7ec4\u7ec7\uff0c\u5f53\u7136\uff0c\u5982\u679c\u6709\u8d85\u8fc710\u4e2a\u5206\u652f\uff0c\u5c31\u4e0d\u8981\u4f7f\u7528<code>switch\/case<\/code>\u4e86\u3002<\/p>\n<h3 id=\"37\u3001\u5728switch\/case\u4e2d\u4f7f\u7528\u6570\u5b57\u533a\u95f4\">37\u3001\u5728<code>switch\/case<\/code>\u4e2d\u4f7f\u7528\u6570\u5b57\u533a\u95f4<\/h3>\n<p>\u5176\u5b9e\uff0c<code>switch\/case<\/code>\u4e2d\u7684<code>case<\/code>\u6761\u4ef6\uff0c\u8fd8\u53ef\u4ee5\u8fd9\u6837\u5199\uff1a<\/p>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<div class=\"line\">4<\/div>\n<div class=\"line\">5<\/div>\n<div class=\"line\">6<\/div>\n<div class=\"line\">7<\/div>\n<div class=\"line\">8<\/div>\n<div class=\"line\">9<\/div>\n<div class=\"line\">10<\/div>\n<div class=\"line\">11<\/div>\n<div class=\"line\">12<\/div>\n<div class=\"line\">13<\/div>\n<div class=\"line\">14<\/div>\n<div class=\"line\">15<\/div>\n<div class=\"line\">16<\/div>\n<div class=\"line\">17<\/div>\n<div class=\"line\">18<\/div>\n<div class=\"line\">19<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"function\"><span class=\"keyword\">function<\/span> <span class=\"title\">getCategory<\/span><span class=\"params\">(age)<\/span> <\/span>{<\/div>\n<div class=\"line\"><span class=\"keyword\">var<\/span> category = <span class=\"string\">\u201c\u201d<\/span>;<\/div>\n<div class=\"line\"><span class=\"keyword\">switch<\/span> (<span class=\"literal\">true<\/span>) {<\/div>\n<div class=\"line\"><span class=\"keyword\">case<\/span> <span class=\"built_in\">isNaN<\/span>(age):<\/div>\n<div class=\"line\">category = <span class=\"string\">\u201cnot an age\u201d<\/span>;<\/div>\n<div class=\"line\"><span class=\"keyword\">break<\/span>;<\/div>\n<div class=\"line\"><span class=\"keyword\">case<\/span> (age &gt;= <span class=\"number\">50<\/span>):<\/div>\n<div class=\"line\">category = <span class=\"string\">\u201cOld\u201d<\/span>;<\/div>\n<div class=\"line\"><span class=\"keyword\">break<\/span>;<\/div>\n<div class=\"line\"><span class=\"keyword\">case<\/span> (age &lt;= <span class=\"number\">20<\/span>):<\/div>\n<div class=\"line\">category = <span class=\"string\">\u201cBaby\u201d<\/span>;<\/div>\n<div class=\"line\"><span class=\"keyword\">break<\/span>;<\/div>\n<div class=\"line\"><span class=\"keyword\">default<\/span>:<\/div>\n<div class=\"line\">category = <span class=\"string\">\u201cYoung\u201d<\/span>;<\/div>\n<div class=\"line\"><span class=\"keyword\">break<\/span>;<\/div>\n<div class=\"line\">};<\/div>\n<div class=\"line\"><span class=\"keyword\">return<\/span> category;<\/div>\n<div class=\"line\">}<\/div>\n<div class=\"line\">getCategory(<span class=\"number\">5<\/span>); <span class=\"comment\">\/\/ \u5c06\u8fd4\u56de \u201cBaby\u201d<\/span><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"38\u3001\u4f7f\u7528\u5bf9\u8c61\u4f5c\u4e3a\u5bf9\u8c61\u7684\u539f\u578b\">38\u3001\u4f7f\u7528\u5bf9\u8c61\u4f5c\u4e3a\u5bf9\u8c61\u7684\u539f\u578b<\/h3>\n<p>\u4e0b\u9762\u8fd9\u6837\uff0c\u4fbf\u53ef\u4ee5\u7ed9\u5b9a\u5bf9\u8c61\u4f5c\u4e3a\u53c2\u6570\uff0c\u6765\u521b\u5efa\u4ee5\u6b64\u4e3a\u539f\u578b\u7684\u65b0\u5bf9\u8c61\uff1a<\/p>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<div class=\"line\">4<\/div>\n<div class=\"line\">5<\/div>\n<div class=\"line\">6<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"function\"><span class=\"keyword\">function<\/span> <span class=\"title\">clone<\/span><span class=\"params\">(object)<\/span> <\/span>{<\/div>\n<div class=\"line\"><span class=\"function\"><span class=\"keyword\">function<\/span> <span class=\"title\">OneShotConstructor<\/span><span class=\"params\">()<\/span><\/span>{};<\/div>\n<div class=\"line\">OneShotConstructor.prototype = object;<\/div>\n<div class=\"line\"><span class=\"keyword\">return<\/span> <span class=\"keyword\">new<\/span> OneShotConstructor();<\/div>\n<div class=\"line\">}<\/div>\n<div class=\"line\">clone(<span class=\"built_in\">Array<\/span>).prototype ; <span class=\"comment\">\/\/ []<\/span><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"39\u3001HTML\u5b57\u6bb5\u8f6c\u6362\u51fd\u6570\">39\u3001HTML\u5b57\u6bb5\u8f6c\u6362\u51fd\u6570<\/h3>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<div class=\"line\">4<\/div>\n<div class=\"line\">5<\/div>\n<div class=\"line\">6<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"function\"><span class=\"keyword\">function<\/span> <span class=\"title\">escapeHTML<\/span><span class=\"params\">(text)<\/span> <\/span>{<\/div>\n<div class=\"line\"><span class=\"keyword\">var<\/span> replacements= {<span class=\"string\">\u201c&lt;\u201c<\/span>: <span class=\"string\">\u201c&lt;\u201c<\/span>, <span class=\"string\">\u201c&gt;\u201d<\/span>: <span class=\"string\">\u201c&gt;\u201d<\/span>,<span class=\"string\">\u201c&amp;\u201d<\/span>: <span class=\"string\">\u201c&amp;\u201d<\/span>, <span class=\"string\">\u201c\\\u201d\u201d<\/span>: <span class=\"string\">\u201c\u201d\u201d<\/span>};<\/div>\n<div class=\"line\"><span class=\"keyword\">return<\/span> text.replace(<span class=\"regexp\">\/[&lt;&gt;&amp;\u201d]\/g<\/span>, <span class=\"function\"><span class=\"keyword\">function<\/span><span class=\"params\">(character)<\/span> <\/span>{<\/div>\n<div class=\"line\"><span class=\"keyword\">return<\/span> replacements[character];<\/div>\n<div class=\"line\">});<\/div>\n<div class=\"line\">}<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"40\u3001\u4e0d\u8981\u5728\u5faa\u73af\u5185\u90e8\u4f7f\u7528try-catch-finally\">40\u3001\u4e0d\u8981\u5728\u5faa\u73af\u5185\u90e8\u4f7f\u7528try-catch-finally<\/h3>\n<p>try-catch-finally\u4e2dcatch\u90e8\u5206\u5728\u6267\u884c\u65f6\u4f1a\u5c06\u5f02\u5e38\u8d4b\u7ed9\u4e00\u4e2a\u53d8\u91cf\uff0c\u8fd9\u4e2a\u53d8\u91cf\u4f1a\u88ab\u6784\u5efa\u6210\u4e00\u4e2a\u8fd0\u884c\u65f6\u4f5c\u7528\u57df\u5185\u7684\u65b0\u7684\u53d8\u91cf\u3002<\/p>\n<p>\u5207\u5fcc\uff1a<\/p>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<div class=\"line\">4<\/div>\n<div class=\"line\">5<\/div>\n<div class=\"line\">6<\/div>\n<div class=\"line\">7<\/div>\n<div class=\"line\">8<\/div>\n<div class=\"line\">9<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> object = [<span class=\"string\">\u2018foo\u2019<\/span>, <span class=\"string\">\u2018bar\u2019<\/span>], i;<\/div>\n<div class=\"line\"><span class=\"keyword\">for<\/span> (i = <span class=\"number\">0<\/span>, len = object.length; i &lt;len; i++) {<\/div>\n<div class=\"line\"><span class=\"keyword\">try<\/span> {<\/div>\n<div class=\"line\"><span class=\"comment\">\/\/ do something that throws an exception <\/span><\/div>\n<div class=\"line\">}<\/div>\n<div class=\"line\"><span class=\"keyword\">catch<\/span> (e) {<\/div>\n<div class=\"line\"><span class=\"comment\">\/\/ handle exception <\/span><\/div>\n<div class=\"line\">}<\/div>\n<div class=\"line\">}<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>\u800c\u5e94\u8be5\uff1a<\/p>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<div class=\"line\">4<\/div>\n<div class=\"line\">5<\/div>\n<div class=\"line\">6<\/div>\n<div class=\"line\">7<\/div>\n<div class=\"line\">8<\/div>\n<div class=\"line\">9<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> object = [<span class=\"string\">\u2018foo\u2019<\/span>, <span class=\"string\">\u2018bar\u2019<\/span>], i;<\/div>\n<div class=\"line\"><span class=\"keyword\">try<\/span> {<\/div>\n<div class=\"line\"><span class=\"keyword\">for<\/span> (i = <span class=\"number\">0<\/span>, len = object.length; i &lt;len; i++) {<\/div>\n<div class=\"line\"><span class=\"comment\">\/\/ do something that throws an exception <\/span><\/div>\n<div class=\"line\">}<\/div>\n<div class=\"line\">}<\/div>\n<div class=\"line\"><span class=\"keyword\">catch<\/span> (e) {<\/div>\n<div class=\"line\"><span class=\"comment\">\/\/ handle exception <\/span><\/div>\n<div class=\"line\">}<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"41\u3001\u4f7f\u7528XMLHttpRequests\u65f6\u6ce8\u610f\u8bbe\u7f6e\u8d85\u65f6\">41\u3001\u4f7f\u7528XMLHttpRequests\u65f6\u6ce8\u610f\u8bbe\u7f6e\u8d85\u65f6<\/h3>\n<p>XMLHttpRequests\u5728\u6267\u884c\u65f6\uff0c\u5f53\u957f\u65f6\u95f4\u6ca1\u6709\u54cd\u5e94\uff08\u5982\u51fa\u73b0\u7f51\u7edc\u95ee\u9898\u7b49\uff09\u65f6\uff0c\u5e94\u8be5\u4e2d\u6b62\u6389\u8fde\u63a5\uff0c\u53ef\u4ee5\u901a\u8fc7<code>setTimeout()<\/code>\u6765\u5b8c\u6210\u8fd9\u4e2a\u5de5\u4f5c\uff1a<\/p>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<div class=\"line\">4<\/div>\n<div class=\"line\">5<\/div>\n<div class=\"line\">6<\/div>\n<div class=\"line\">7<\/div>\n<div class=\"line\">8<\/div>\n<div class=\"line\">9<\/div>\n<div class=\"line\">10<\/div>\n<div class=\"line\">11<\/div>\n<div class=\"line\">12<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> xhr = <span class=\"keyword\">new<\/span> XMLHttpRequest ();<\/div>\n<div class=\"line\">xhr.onreadystatechange = <span class=\"function\"><span class=\"keyword\">function<\/span> <span class=\"params\">()<\/span> <\/span>{<\/div>\n<div class=\"line\"><span class=\"keyword\">if<\/span> (<span class=\"keyword\">this<\/span>.readyState == <span class=\"number\">4<\/span>) {<\/div>\n<div class=\"line\">clearTimeout(timeout);<\/div>\n<div class=\"line\"><span class=\"comment\">\/\/ do something with response data <\/span><\/div>\n<div class=\"line\">}<\/div>\n<div class=\"line\">}<\/div>\n<div class=\"line\"><span class=\"keyword\">var<\/span> timeout = setTimeout( <span class=\"function\"><span class=\"keyword\">function<\/span> <span class=\"params\">()<\/span> <\/span>{<\/div>\n<div class=\"line\">xhr.abort(); <span class=\"comment\">\/\/ call error callback <\/span><\/div>\n<div class=\"line\">}, <span class=\"number\">60<\/span>*<span class=\"number\">1000<\/span> <span class=\"comment\">\/* timeout after a minute *\/<\/span> );<\/div>\n<div class=\"line\">xhr.open(<span class=\"string\">\u2018GET\u2019<\/span>, url, <span class=\"literal\">true<\/span>);<\/div>\n<div class=\"line\">xhr.send();<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>\u540c\u65f6\u9700\u8981\u6ce8\u610f\u7684\u662f\uff0c\u4e0d\u8981\u540c\u65f6\u53d1\u8d77\u591a\u4e2aXMLHttpRequests\u8bf7\u6c42\u3002<\/p>\n<h3 id=\"42\u3001\u5904\u7406WebSocket\u7684\u8d85\u65f6\">42\u3001\u5904\u7406WebSocket\u7684\u8d85\u65f6<\/h3>\n<p>\u901a\u5e38\u60c5\u51b5\u4e0b\uff0cWebSocket\u8fde\u63a5\u521b\u5efa\u540e\uff0c\u5982\u679c30\u79d2\u5185\u6ca1\u6709\u4efb\u4f55\u6d3b\u52a8\uff0c\u670d\u52a1\u5668\u7aef\u4f1a\u5bf9\u8fde\u63a5\u8fdb\u884c\u8d85\u65f6\u5904\u7406\uff0c\u9632\u706b\u5899\u4e5f\u53ef\u4ee5\u5bf9\u5355\u4f4d\u5468\u671f\u6ca1\u6709\u6d3b\u52a8\u7684\u8fde\u63a5\u8fdb\u884c\u8d85\u65f6\u5904\u7406\u3002<\/p>\n<p>\u4e3a\u4e86\u9632\u6b62\u8fd9\u79cd\u60c5\u51b5\u7684\u53d1\u751f\uff0c\u53ef\u4ee5\u6bcf\u9694\u4e00\u5b9a\u65f6\u95f4\uff0c\u5f80\u670d\u52a1\u5668\u53d1\u9001\u4e00\u6761\u7a7a\u7684\u6d88\u606f\u3002\u53ef\u4ee5\u901a\u8fc7\u4e0b\u9762\u8fd9\u4e24\u4e2a\u51fd\u6570\u6765\u5b9e\u73b0\u8fd9\u4e2a\u9700\u6c42\uff0c\u4e00\u4e2a\u7528\u4e8e\u4f7f\u8fde\u63a5\u4fdd\u6301\u6d3b\u52a8\u72b6\u6001\uff0c\u53e6\u4e00\u4e2a\u4e13\u95e8\u7528\u4e8e\u7ed3\u675f\u8fd9\u4e2a\u72b6\u6001\u3002<\/p>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<div class=\"line\">3<\/div>\n<div class=\"line\">4<\/div>\n<div class=\"line\">5<\/div>\n<div class=\"line\">6<\/div>\n<div class=\"line\">7<\/div>\n<div class=\"line\">8<\/div>\n<div class=\"line\">9<\/div>\n<div class=\"line\">10<\/div>\n<div class=\"line\">11<\/div>\n<div class=\"line\">12<\/div>\n<div class=\"line\">13<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> timerID = <span class=\"number\">0<\/span>;<\/div>\n<div class=\"line\"><span class=\"function\"><span class=\"keyword\">function<\/span> <span class=\"title\">keepAlive<\/span><span class=\"params\">()<\/span> <\/span>{<\/div>\n<div class=\"line\"><span class=\"keyword\">var<\/span> timeout = <span class=\"number\">15000<\/span>;<\/div>\n<div class=\"line\"><span class=\"keyword\">if<\/span> (webSocket.readyState == webSocket.OPEN) {<\/div>\n<div class=\"line\">webSocket.send(<span class=\"string\">\u201d<\/span>);<\/div>\n<div class=\"line\">}<\/div>\n<div class=\"line\">timerId = setTimeout(keepAlive, timeout);<\/div>\n<div class=\"line\">}<\/div>\n<div class=\"line\"><span class=\"function\"><span class=\"keyword\">function<\/span> <span class=\"title\">cancelKeepAlive<\/span><span class=\"params\">()<\/span> <\/span>{<\/div>\n<div class=\"line\"><span class=\"keyword\">if<\/span> (timerId) {<\/div>\n<div class=\"line\">cancelTimeout(timerId);<\/div>\n<div class=\"line\">}<\/div>\n<div class=\"line\">}<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p><code>keepAlive()<\/code>\u51fd\u6570\u53ef\u4ee5\u653e\u5728WebSocket\u8fde\u63a5\u7684<code>onOpen()<\/code>\u65b9\u6cd5\u7684\u6700\u540e\u9762\uff0c<code>cancelKeepAlive()<\/code>\u653e\u5728<code>onClose()<\/code>\u65b9\u6cd5\u7684\u6700\u672b\u5c3e\u3002<\/p>\n<h3 id=\"43\u3001\u65f6\u95f4\u6ce8\u610f\u539f\u59cb\u64cd\u4f5c\u7b26\u6bd4\u51fd\u6570\u8c03\u7528\u5feb\uff0c\u4f7f\u7528VanillaJS\">43\u3001\u65f6\u95f4\u6ce8\u610f\u539f\u59cb\u64cd\u4f5c\u7b26\u6bd4\u51fd\u6570\u8c03\u7528\u5feb\uff0c\u4f7f\u7528VanillaJS<\/h3>\n<p>\u6bd4\u5982\uff0c\u4e00\u822c\u4e0d\u8981\u8fd9\u6837\uff1a<\/p>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> min = <span class=\"built_in\">Math<\/span>.min(a,b);<\/div>\n<div class=\"line\">A.push(v);<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>\u53ef\u4ee5\u8fd9\u6837\u6765\u4ee3\u66ff\uff1a<\/p>\n<figure class=\"highlight js\">\n<table>\n<tbody>\n<tr>\n<td class=\"gutter\">\n<div class=\"line\">1<\/div>\n<div class=\"line\">2<\/div>\n<\/td>\n<td class=\"code\">\n<div class=\"line\"><span class=\"keyword\">var<\/span> min = a &lt; b ? a : b;<\/div>\n<div class=\"line\">A[A.length] = v;<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"44\u3001\u5f00\u53d1\u65f6\u6ce8\u610f\u4ee3\u7801\u7ed3\u6784\uff0c\u4e0a\u7ebf\u65f6\u538b\u7f29JavaScript\u4ee3\u7801\">44\u3001\u5f00\u53d1\u65f6\u6ce8\u610f\u4ee3\u7801\u7ed3\u6784\uff0c\u4e0a\u7ebf\u65f6\u538b\u7f29JavaScript\u4ee3\u7801<\/h3>\n<p>\u53ef\u4ee5\u4f7f\u7528JSLint\u6216JSMin\u7b49\u65b9\u6cd5\u6765\u538b\u7f29\u4ee3\u7801\u3002<\/p>\n<h3 id=\"45\u3001JavaScript\u535a\u5927\u7cbe\u6df1\uff0c\u8fd9\u91cc\u6709\u4e9b\u4e0d\u9519\u7684\u5b66\u4e60\u8d44\u6e90\">45\u3001JavaScript\u535a\u5927\u7cbe\u6df1\uff0c\u8fd9\u91cc\u6709\u4e9b\u4e0d\u9519\u7684\u5b66\u4e60\u8d44\u6e90<\/h3>\n<ul>\n<li>Code Academy\u8d44\u6e90\uff1ahttp:\/\/www.codecademy.com\/tracks\/javascript<\/li>\n<li>Marjin Haverbekex\u7f16\u5199\u7684<em>Eloquent JavaScript<\/em>\uff1ahttp:\/\/eloquentjavascript.net\/<\/li>\n<li>John Resig\u7f16\u5199\u7684<em>Advanced JavaScript<\/em>\uff1ahttp:\/\/ejohn.org\/apps\/learn\/<\/li>\n<\/ul>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>\u672c\u6587\u662f\u4e00\u7bc7\u7ffb\u8bd1\u6587\u7ae0\uff0c\u539f\u6587\u4fe1\u606f\u5982\u4e0b\uff1a \u539f\u6587\uff1a45 Useful JavaScript Tips, Tricks &#8230;<\/p>\n","protected":false},"author":1,"featured_media":1466,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_kad_post_transparent":"","_kad_post_title":"","_kad_post_layout":"","_kad_post_sidebar_id":"","_kad_post_content_style":"","_kad_post_vertical_padding":"","_kad_post_feature":"","_kad_post_feature_position":"","_kad_post_header":false,"_kad_post_footer":false,"footnotes":""},"categories":[38,60],"tags":[233],"_links":{"self":[{"href":"http:\/\/www.daliane.com\/category\/jinjiaoyou\/wp-json\/wp\/v2\/posts\/1475"}],"collection":[{"href":"http:\/\/www.daliane.com\/category\/jinjiaoyou\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.daliane.com\/category\/jinjiaoyou\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.daliane.com\/category\/jinjiaoyou\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.daliane.com\/category\/jinjiaoyou\/wp-json\/wp\/v2\/comments?post=1475"}],"version-history":[{"count":1,"href":"http:\/\/www.daliane.com\/category\/jinjiaoyou\/wp-json\/wp\/v2\/posts\/1475\/revisions"}],"predecessor-version":[{"id":1476,"href":"http:\/\/www.daliane.com\/category\/jinjiaoyou\/wp-json\/wp\/v2\/posts\/1475\/revisions\/1476"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/www.daliane.com\/category\/jinjiaoyou\/wp-json\/wp\/v2\/media\/1466"}],"wp:attachment":[{"href":"http:\/\/www.daliane.com\/category\/jinjiaoyou\/wp-json\/wp\/v2\/media?parent=1475"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.daliane.com\/category\/jinjiaoyou\/wp-json\/wp\/v2\/categories?post=1475"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.daliane.com\/category\/jinjiaoyou\/wp-json\/wp\/v2\/tags?post=1475"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}