{"id":3220,"date":"2013-04-25T21:43:49","date_gmt":"2013-04-25T13:43:49","guid":{"rendered":"http:\/\/www.zhangxinxu.com\/wordpress\/?p=3220"},"modified":"2018-01-02T02:49:11","modified_gmt":"2018-01-01T18:49:11","slug":"es5%e6%96%b0%e5%a2%9e%e6%95%b0%e7%bb%84%e6%96%b9%e6%b3%95","status":"publish","type":"post","link":"https:\/\/www.zhangxinxu.com\/wordpress\/2013\/04\/es5%e6%96%b0%e5%a2%9e%e6%95%b0%e7%bb%84%e6%96%b9%e6%b3%95\/","title":{"rendered":"ES5\u4e2d\u65b0\u589e\u7684Array\u65b9\u6cd5\u8be6\u7ec6\u8bf4\u660e"},"content":{"rendered":"<p>by <a href=\"http:\/\/www.zhangxinxu.com\/\">zhangxinxu<\/a> from <a href=\"http:\/\/www.zhangxinxu.com\/\">http:\/\/www.zhangxinxu.com<\/a><br \/>\n\u672c\u6587\u5730\u5740\uff1a<a href=\"http:\/\/www.zhangxinxu.com\/wordpress\/?p=3220\">http:\/\/www.zhangxinxu.com\/wordpress\/?p=3220<\/a><\/p>\n<style>.zxx_code .comment{color:green;}<\/style>\n<h3>\u4e00\u3001\u524d\u8a00-\u7d22\u5f15<\/h3>\n<p>ES5\u4e2d\u65b0\u589e\u7684\u4e0d\u5c11\u4e1c\u897f\uff0c\u4e86\u89e3\u4e4b\u5bf9\u6211\u4eec\u5199JavaScript\u4f1a\u6709\u4e0d\u5c11\u5e2e\u52a9\uff0c\u6bd4\u5982\u6570\u7ec4\u8fd9\u5757\uff0c\u6211\u4eec\u53ef\u80fd\u5c31\u4e0d\u9700\u8981\u53bb\u6709\u677f\u6709\u773c\u5730<code>for<\/code>\u5faa\u73af\u4e86\u3002<\/p>\n<p>ES5\u4e2d\u65b0\u589e\u4e86\u5199\u6570\u7ec4\u65b9\u6cd5\uff0c\u5982\u4e0b\uff1a<\/p>\n<ol>\n<li><a title=\"forEach\" href=\"#foreach\">forEach<\/a> (js v1.6)<\/li>\n<li><a title=\"map\" href=\"#map\">map<\/a> (js v1.6)<\/li>\n<li><a title=\"filter\" href=\"#filter\">filter<\/a> (js v1.6)<\/li>\n<li><a title=\"some\" href=\"#some\">some<\/a> (js v1.6)<\/li>\n<li><a title=\"every\" href=\"#every\">every<\/a> (js v1.6)<\/li>\n<li><a title=\"indexOf\" href=\"#indexof\">indexOf<\/a> (js v1.6)<\/li>\n<li><a title=\"lastIndexOf\" href=\"#lastindexof\">lastIndexOf<\/a> (js v1.6)<\/li>\n<li><a title=\"reduce\" href=\"#reduce\">reduce<\/a> (js v1.8)<\/li>\n<li><a title=\"reduceRight\" href=\"#reduceright\">reduceRight<\/a> (js v1.8)<\/li>\n<\/ol>\n<p><strong>\u6d4f\u89c8\u5668\u652f\u6301<\/strong><\/p>\n<ul>\n<li>Opera 11+<\/li>\n<li>Firefox 3.6+<\/li>\n<li>Safari 5+<\/li>\n<li>Chrome 8+<\/li>\n<li>Internet Explorer 9+<\/li>\n<\/ul>\n<p>\u5bf9\u4e8e\u8ba9\u4eba\u5931\u671b\u5f88\u591a\u6b21\u7684IE6-IE8\u6d4f\u89c8\u5668\uff0cArray\u539f\u578b\u6269\u5c55\u53ef\u4ee5\u5b9e\u73b0\u4ee5\u4e0a\u5168\u90e8\u529f\u80fd\uff0c\u4f8b\u5982<code>forEach<\/code>\u65b9\u6cd5:<\/p>\n<div class=\"zxx_code\">\n<pre><span class=\"comment\" style=\"color:green;\">\/\/ \u5bf9\u4e8e\u53e4\u8463\u6d4f\u89c8\u5668\uff0c\u5982IE6-IE8<\/span>\n\n<span class=\"keyword\">if<\/span> (typeof <span class=\"keyword\">Array<\/span>.prototype.<span class=\"keyword\">forEach<\/span> != <span class=\"string\">\"function\"<\/span>) {\n  <span class=\"keyword\">Array<\/span>.prototype.<span class=\"keyword\">forEach<\/span> = <span class=\"keyword\">function<\/span> () {\n    <span class=\"comment\" style=\"color:green;\">\/* \u5b9e\u73b0 *\/<\/span>\n  };\n}\n<\/pre>\n<\/div>\n<h3>\u4e8c\u3001\u4e00\u4e2a\u4e00\u4e2a\u6765<\/h3>\n<ol>\n<li><strong id=\"foreach\">forEach<\/strong><br \/>\n<code>forEach<\/code>\u662fArray\u65b0\u65b9\u6cd5\u4e2d\u6700\u57fa\u672c\u7684\u4e00\u4e2a\uff0c\u5c31\u662f\u904d\u5386\uff0c\u5faa\u73af\u3002\u4f8b\u5982\u4e0b\u9762\u8fd9\u4e2a\u4f8b\u5b50\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre><span class=\"attr_selector\">[1, 2 ,3, 4]<\/span><span class=\"class\">.forEach<\/span>(<span class=\"tag\">alert<\/span>);<\/pre>\n<\/div>\n<p>\u7b49\u540c\u4e8e\u4e0b\u9762\u8fd9\u4e2a\u4f20\u7edf\u7684<code>for<\/code>\u5faa\u73af\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre><span class=\"keyword\">var<\/span> <span class=\"keyword\">array<\/span> = [<span class=\"number\">1<\/span>, <span class=\"number\">2<\/span>, <span class=\"number\">3<\/span>, <span class=\"number\">4<\/span>];\n\n<span class=\"keyword\">for<\/span> (<span class=\"keyword\">var<\/span> k = <span class=\"number\">0<\/span>, length = <span class=\"keyword\">array<\/span>.length; k &lt; length; k++) {\n  alert(<span class=\"keyword\">array<\/span>[k]);\n}<\/pre>\n<\/div>\n<p>Array\u5728ES5\u65b0\u589e\u7684\u65b9\u6cd5\u4e2d\uff0c\u53c2\u6570\u90fd\u662f<code>function<\/code>\u7c7b\u578b\uff0c\u9ed8\u8ba4\u6709\u4f20\u53c2\uff0c\u8fd9\u4e9b\u53c2\u6570\u5206\u522b\u662f\uff1f\u89c1\u4e0b\u9762\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre>[<span class=\"number\">1<\/span>, <span class=\"number\">2<\/span> ,<span class=\"number\">3<\/span>, <span class=\"number\">4<\/span>].<span class=\"keyword\">forEach<\/span>(console.log);\n\n<span class=\"comment\">\/\/ \u7ed3\u679c\uff1a<\/span>\n\n<span class=\"comment\">\/\/ 1, 0, [1, 2, 3, 4]<\/span>\n<span class=\"comment\">\/\/ 2, 1, [1, 2, 3, 4]<\/span>\n<span class=\"comment\">\/\/ 3, 2, [1, 2, 3, 4]<\/span>\n<span class=\"comment\">\/\/ 4, 3, [1, 2, 3, 4]<\/span><\/pre>\n<\/div>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/image.zhangxinxu.com\/image\/blog\/201304\/2013-04-24_230237.png\" width=\"409\" height=\"143\" alt=\"\u7528\u6765\u5224\u65ad\u53c2\u6570\u4e2a\u6570\u4ee5\u53ca\u5185\u5bb9\u7684\u6d4b\u8bd5\u8f93\u51fa\u622a\u56fe \u5f20\u946b\u65ed-\u946b\u7a7a\u95f4-\u946b\u751f\u6d3b\" class=\"alignnone\" \/><\/p>\n<p>\u663e\u800c\u6613\u89c1\uff0c<code>forEach<\/code>\u65b9\u6cd5\u4e2d\u7684<code>function<\/code>\u56de\u8c03\u652f\u63013\u4e2a\u53c2\u6570\uff0c\u7b2c1\u4e2a\u662f\u904d\u5386\u7684\u6570\u7ec4\u5185\u5bb9\uff1b\u7b2c2\u4e2a\u662f\u5bf9\u5e94\u7684\u6570\u7ec4\u7d22\u5f15\uff0c\u7b2c3\u4e2a\u662f\u6570\u7ec4\u672c\u8eab\u3002<\/p>\n<p>\u56e0\u6b64\uff0c\u6211\u4eec\u6709\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre>[].forEach(function(<span style=\"color:#cd0000;\">value, index<\/span>, array) {\n    <span class=\"comment\">\/\/ ...<\/span>\n});<\/pre>\n<\/div>\n<p>\u5bf9\u6bd4jQuery\u4e2d\u7684<code>$.each<\/code>\u65b9\u6cd5\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre>$.each([], function(<span style=\"color:#cd0000;\">index, value<\/span>, array) {\n    <span class=\"comment\">\/\/ ...<\/span>\n});<\/pre>\n<\/div>\n<p>\u4f1a\u53d1\u73b0\uff0c\u7b2c1\u4e2a\u548c\u7b2c2\u4e2a\u53c2\u6570\u6b63\u597d\u662f\u76f8\u53cd\u7684\uff0c\u5927\u5bb6\u8981\u6ce8\u610f\u4e86\uff0c\u4e0d\u8981\u8bb0\u9519\u4e86\u3002\u540e\u9762\u7c7b\u4f3c\u7684\u65b9\u6cd5\uff0c\u4f8b\u5982<code>$.map<\/code>\u4e5f\u662f\u5982\u6b64\u3002<\/p>\n<p>\u73b0\u5728\uff0c\u6211\u4eec\u5c31\u53ef\u4ee5\u4f7f\u7528<code>forEach<\/code>\u5356\u5f04\u4e00\u4e2a\u7a0d\u663e\u5b8c\u6574\u7684\u4f8b\u5b50\u4e86\uff0c\u6570\u7ec4\u6c42\u548c\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre><span class=\"identifier\">var<\/span> <span class=\"identifier\"><span class=\"keymethods\">sum<\/span><\/span> = <span class=\"number\">0<\/span>;\n\n[<span class=\"number\">1<\/span>, <span class=\"number\">2<\/span>, <span class=\"number\">3<\/span>, <span class=\"number\">4<\/span>].<span class=\"constant\">forEach<\/span>(<span class=\"identifier\">function<\/span> (<span class=\"identifier\">item<\/span>, <span class=\"identifier\"><span class=\"keymethods\">index<\/span><\/span>, <span class=\"identifier\">array<\/span>) {\n  <span class=\"identifier\">console<\/span>.<span class=\"identifier\">log<\/span>(<span class=\"identifier\">array<\/span>[<span class=\"identifier\"><span class=\"keymethods\">index<\/span><\/span>] == <span class=\"identifier\">item<\/span>); <span class=\"comment\">\/\/<\/span> <span class=\"identifier\"><span class=\"comment\">true<\/span><\/span>\n  <span class=\"identifier\"><span class=\"keymethods\">sum<\/span><\/span> += <span class=\"identifier\">item<\/span>;\n});\n\n<span class=\"identifier\">alert<\/span>(<span class=\"identifier\"><span class=\"keymethods\">sum<\/span><\/span>); <span class=\"comment\">\/\/<\/span> <span class=\"comment\">10<\/span><\/pre>\n<\/div>\n<p>\u518d\u4e0b\u9762\uff0c\u66f4\u8fdb\u4e00\u6b65\uff0c<code>forEach<\/code>\u9664\u4e86\u63a5\u53d7\u4e00\u4e2a\u5fc5\u987b\u7684\u56de\u8c03\u51fd\u6570\u53c2\u6570\uff0c\u8fd8\u53ef\u4ee5\u63a5\u53d7\u4e00\u4e2a\u53ef\u9009\u7684\u4e0a\u4e0b\u6587\u53c2\u6570\uff08\u6539\u53d8\u56de\u8c03\u51fd\u6570\u91cc\u9762\u7684<code>this<\/code>\u6307\u5411\uff09\uff08\u7b2c2\u4e2a\u53c2\u6570\uff09\u3002<\/p>\n<div class=\"zxx_code\">\n<pre>array.forEach(callback,[ thisObject])<\/pre>\n<\/div>\n<p>\u4f8b\u5b50\u66f4\u80fd\u8bf4\u660e\u4e00\u5207\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre>var database = {\n  users: [\"\u5f20\u542b\u97f5\", \"\u6c5f\u4e00\u71d5\", \"\u674e\u5c0f\u7490\"],\n  sendEmail: function (user) {\n    if (<span style=\"color:#cd0000;\">this<\/span>.isValidUser(user)) {\n      console.log(\"\u4f60\u597d\uff0c\" + user);\n    } else {\n      console.log(\"\u62b1\u6b49\uff0c\"+ user +\"\uff0c\u4f60\u4e0d\u662f\u672c\u5bb6\u4eba\");\t\n    }\n  },\n  isValidUser: function (user) {\n    return \/^\u5f20\/.test(user);\n  }\n};\n\n\/\/ \u7ed9\u6bcf\u4e2a\u4eba\u6cd5\u90ae\u4ef6\ndatabase.users.forEach(  <span class=\"comment\">\/\/ database.users\u4e2d\u4eba\u904d\u5386<\/span>\n  database.sendEmail,    <span class=\"comment\">\/\/ \u53d1\u9001\u90ae\u4ef6<\/span>\n  database               <span class=\"comment\">\/\/ \u4f7f\u7528database\u4ee3\u66ff\u4e0a\u9762\u6807\u7ea2\u7684this<\/span>\n);\n\n<span class=\"comment\">\/\/ \u7ed3\u679c\uff1a\n\/\/ \u4f60\u597d\uff0c\u5f20\u542b\u97f5\n\/\/ \u62b1\u6b49\uff0c\u6c5f\u4e00\u71d5\uff0c\u4f60\u4e0d\u662f\u672c\u5bb6\u4eba\n\/\/ \u62b1\u6b49\uff0c\u674e\u5c0f\u7490\uff0c\u4f60\u4e0d\u662f\u672c\u5bb6<\/span><\/pre>\n<\/div>\n<p>\u5982\u679c\u8fd9\u7b2c2\u4e2a\u53ef\u9009\u53c2\u6570\u4e0d\u6307\u5b9a\uff0c\u5219\u4f7f\u7528\u5168\u5c40\u5bf9\u8c61\u4ee3\u66ff\uff08\u5728\u6d4f\u89c8\u5668\u662f\u4e3a<code>window<\/code>\uff09\uff0c<a href=\"http:\/\/dmitrysoshnikov.com\/ecmascript\/es5-chapter-2-strict-mode\/\">\u4e25\u683c\u6a21\u5f0f<\/a>\u4e0b\u751a\u81f3\u662f<code>undefined<\/code>.<\/p>\n<p>\u53e6\u5916\uff0cforEach\u4e0d\u4f1a\u904d\u5386\u7eaf\u7cb9\u201c\u5360\u7740\u5b98\u4f4d\u5403\u7a7a\u9977\u201d\u7684\u5143\u7d20\u7684\uff0c\u4f8b\u5982\u4e0b\u9762\u8fd9\u4e2a\u4f8b\u5b50\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre><span class=\"keyword\">var<\/span> <span class=\"keyword\">array<\/span> = [<span class=\"number\">1<\/span>, <span class=\"number\">2<\/span>, <span class=\"number\">3<\/span>];\n\ndelete <span class=\"keyword\">array<\/span>[<span class=\"number\">1<\/span>]; <span class=\"comment\">\/\/ \u79fb\u9664 2<\/span>\nalert(<span class=\"keyword\">array<\/span>); <span class=\"comment\">\/\/ \"1,,3\"<\/span>\n\nalert(<span class=\"keyword\">array<\/span>.length); <span class=\"comment\">\/\/ but the length is still 3<\/span>\n\n<span class=\"keyword\">array<\/span>.<span class=\"keyword\">forEach<\/span>(alert); <span class=\"comment\">\/\/ \u5f39\u51fa\u7684\u4ec5\u4ec5\u662f1\u548c3<\/span><\/pre>\n<\/div>\n<p>\u7efc\u4e0a\u5168\u90e8\u89c4\u5219\uff0c\u6211\u4eec\u5c31\u53ef\u4ee5\u5bf9IE6-IE8\u8fdb\u884c\u4eff\u771f\u6269\u5c55\u4e86\uff0c\u5982\u4e0b\u4ee3\u7801\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre><span class=\"comment\" style=\"color:green;\">\/\/ \u5bf9\u4e8e\u53e4\u8463\u6d4f\u89c8\u5668\uff0c\u5982IE6-IE8<\/span>\n\n<span class=\"keyword\">if<\/span> (typeof <span class=\"keyword\">Array<\/span>.prototype.<span class=\"keyword\">forEach<\/span> != <span class=\"string\">\"function\"<\/span>) {\n  <span class=\"keyword\">Array<\/span>.prototype.<span class=\"keyword\">forEach<\/span> = <span class=\"keyword\">function<\/span> (fn, context) {\n    for (var k = 0, length = this.length; k < length; k++) {\n      if (typeof fn === \"function\" &#038;&#038; Object.prototype.hasOwnProperty.call(this, k)) {\n        fn.call(context, this[k], k, this);\n      }\n    }\n  };\n}\n<\/pre>\n<\/div>\n<p>\u73b0\u5728\u62ff\u4e0a\u9762\u201c\u5f20\u542b\u97f5\u201d\u7684\u4f8b\u5b50\u6d4b\u4e0b\u6211\u4eec\u6269\u5c55\u7684<code>forEach<\/code>\u65b9\u6cd5\uff0c\u60a8\u53ef\u80fd\u72e0\u72e0\u5730\u70b9\u51fb\u8fd9\u91cc\uff1a<a href=\"http:\/\/www.zhangxinxu.com\/study\/201304\/array-foreach.html\" target=\"_blank\" class=\"a_link\">\u517c\u5bb9\u5904\u7406\u7684forEach\u65b9\u6cd5demo<\/a><\/p>\n<p>\u4f8b\u5982IE7\u6d4f\u89c8\u5668\u4e0b\uff1a<br \/>\n<img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/image.zhangxinxu.com\/image\/blog\/201304\/2013-04-25_102546.png\" width=\"281\" height=\"132\" alt=\"IE7\u4e0bforEach\u65b9\u6cd5\u6d4b\u8bd5\u7ed3\u679c\u622a\u56fe \u5f20\u946b\u65ed-\u946b\u7a7a\u95f4-\u946b\u751f\u6d3b\" class=\"alignnone\" \/><\/li>\n<li><strong id=\"map\">map<\/strong><br \/>\n\u8fd9\u91cc\u7684<code>map<\/code>\u4e0d\u662f\u201c\u5730\u56fe\u201d\u7684\u610f\u601d\uff0c\u800c\u662f\u6307\u201c\u6620\u5c04\u201d\u3002<code>[].map();<\/code> \u57fa\u672c\u7528\u6cd5\u8ddf<code>forEach<\/code>\u65b9\u6cd5\u7c7b\u4f3c\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre>array.map(callback,[ thisObject]);<\/pre>\n<\/div>\n<p><code>callback<\/code>\u7684\u53c2\u6570\u4e5f\u7c7b\u4f3c\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre>[].map(function(<span style=\"color:#cd0000;\">value, index<\/span>, array) {\n    <span class=\"comment\">\/\/ ...<\/span>\n});<\/pre>\n<\/div>\n<p><code>map<\/code>\u65b9\u6cd5\u7684\u4f5c\u7528\u4e0d\u96be\u7406\u89e3\uff0c\u201c\u6620\u5c04\u201d\u561b\uff0c\u4e5f\u5c31\u662f\u539f\u6570\u7ec4\u88ab\u201c\u6620\u5c04\u201d\u6210\u5bf9\u5e94\u65b0\u6570\u7ec4\u3002\u4e0b\u9762\u8fd9\u4e2a\u4f8b\u5b50\u662f\u6570\u503c\u9879\u6c42\u5e73\u65b9\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre>var data = [1, 2, 3, 4];\n\nvar arrayOfSquares = data.map(function (item) {\n  return item * item;\n});\n\nalert(arrayOfSquares); <span class=\"comment\">\/\/ 1, 4, 9, 16<\/span><\/pre>\n<\/div>\n<p><code>callback<\/code>\u9700\u8981\u6709<code>return<\/code>\u503c\uff0c\u5982\u679c\u6ca1\u6709\uff0c\u5c31\u50cf\u4e0b\u9762\u8fd9\u6837\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre>var data = [1, 2, 3, 4];\nvar arrayOfSquares = data.map(function() {});\n\narrayOfSquares.forEach(console.log);<\/pre>\n<\/div>\n<p>\u7ed3\u679c\u5982\u4e0b\u56fe\uff0c\u53ef\u4ee5\u770b\u5230\uff0c\u6570\u7ec4\u6240\u6709\u9879\u90fd\u88ab\u6620\u5c04\u6210\u4e86<code>undefined<\/code>\uff1a<br \/>\n<img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/image.zhangxinxu.com\/image\/blog\/201304\/2013-04-25_105958.png\" width=\"410\" height=\"129\" alt=\"\u5168\u90e8\u9879\u90fd\u6210\u4e86undefined \" class=\"alignnone\" \/><\/p>\n<p>\u5728\u5b9e\u9645\u4f7f\u7528\u7684\u65f6\u5019\uff0c\u6211\u4eec\u53ef\u4ee5\u5229\u7528<code>map<\/code>\u65b9\u6cd5\u65b9\u4fbf\u83b7\u5f97\u5bf9\u8c61\u6570\u7ec4\u4e2d\u7684\u7279\u5b9a\u5c5e\u6027\u503c\u4eec\u3002\u4f8b\u5982\u4e0b\u9762\u8fd9\u4e2a\u4f8b\u5b50\uff08\u4e4b\u540e\u7684\u517c\u5bb9demo\u4e5f\u662f\u8be5\u4f8b\u5b50\uff09\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre>var users = [\n  {name: \"\u5f20\u542b\u97f5\", \"email\": \"zhang@email.com\"},\n  {name: \"\u6c5f\u4e00\u71d5\",   \"email\": \"jiang@email.com\"},\n  {name: \"\u674e\u5c0f\u7490\",  \"email\": \"li@email.com\"}\n];\n\nvar emails = users.map(function (user) { return user.email; });\n\nconsole.log(emails.join(\", \")); <span class=\"comment\">\/\/ zhang@email.com, jiang@email.com, li@email.com<\/span><\/pre>\n<\/div>\n<p><code>Array.prototype<\/code>\u6269\u5c55\u53ef\u4ee5\u8ba9IE6-IE8\u6d4f\u89c8\u5668\u4e5f\u652f\u6301<code>map<\/code>\u65b9\u6cd5\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre>if (typeof Array.prototype.map != \"function\") {\n  Array.prototype.map = function (fn, context) {\n    var arr = [];\n    if (typeof fn === \"function\") {\n      for (var k = 0, length = this.length; k < length; k++) {      \n         arr.push(fn.call(context, this[k], k, this));\n      }\n    }\n    return arr;\n  };\n}<\/pre>\n<\/div>\n<p>\u60a8\u53ef\u4ee5\u72e0\u72e0\u5730\u70b9\u51fb\u8fd9\u91cc\uff1a<a href=\"http:\/\/www.zhangxinxu.com\/study\/201304\/array-map.html\" target=\"_blank\" class=\"a_link\">\u517c\u5bb9map\u65b9\u6cd5\u6d4b\u8bd5demo<\/a><\/p>\n<p>\u7ed3\u679c\u663e\u793a\u5982\u4e0b\u56fe\uff0cIE6\u6d4f\u89c8\u5668\uff1a<br \/>\n<img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/image.zhangxinxu.com\/image\/blog\/201304\/2013-04-25_112441.png\" width=\"406\" height=\"146\" alt=\"map\u6620\u5c04\u65b9\u6cd5\u6d4b\u8bd5\uff0cIE6\u4e0b\u622a\u56fe\" class=\"alignnone\" \/><\/li>\n<li><strong id=\"filter\">filter<\/strong><br \/>\n<code>filter<\/code>\u4e3a\u201c\u8fc7\u6ee4\u201d\u3001\u201c\u7b5b\u9009\u201d\u4e4b\u610f\u3002\u6307\u6570\u7ec4<code>filter<\/code>\u540e\uff0c\u8fd4\u56de\u8fc7\u6ee4\u540e\u7684\u65b0\u6570\u7ec4\u3002\u7528\u6cd5\u8ddf<code>map<\/code>\u6781\u4e3a\u76f8\u4f3c\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre>array.filter(callback,[ thisObject]);<\/pre>\n<\/div>\n<p><code>filter<\/code>\u7684<code>callback<\/code>\u51fd\u6570\u9700\u8981\u8fd4\u56de\u5e03\u5c14\u503c<code>true<\/code>\u6216<code>false<\/code>. \u5982\u679c\u4e3a<code>true<\/code>\u5219\u8868\u793a\uff0c\u606d\u559c\u4f60\uff0c\u901a\u8fc7\u5566<img decoding=\"async\" src=\"http:\/\/mat1.gtimg.com\/www\/mb\/images\/face\/188.gif\" align=\"absmiddle\">\uff01\u5982\u679c\u4e3a<code>false<\/code>, \u53ea\u80fd\u9ad8\u6b4c\u201c\u6211\u53ea\u80fd\u65e0\u60c5\u5730\u5c06\u4f60\u629b\u5f03\u2026\u2026\u201d<img decoding=\"async\" src=\"http:\/\/mat1.gtimg.com\/www\/mb\/images\/face\/186.gif\" align=\"absmiddle\">\u3002<\/p>\n<p>\u53ef\u80fd\u4f1a\u7591\u95ee\uff0c\u4e00\u5b9a\u8981\u662f<code>Boolean<\/code>\u503c\u5417\uff1f\u6211\u4eec\u53ef\u4ee5\u7b80\u5355\u6d4b\u8bd5\u4e0b\u561b\uff0c\u5982\u4e0b\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre>var data = [0, 1, 2, 3];\nvar arrayFilter = data.filter(function(item) {\n    return item;\n});\nconsole.log(arrayFilter); <span class=\"comment\">\/\/ [1, 2, 3]<\/span><\/pre>\n<\/div>\n<p>\u6709\u6b64\u53ef\u89c1\uff0c\u8fd4\u56de\u503c\u53ea\u8981\u662f\u5f31\u7b49\u4e8e<code>== true\/false<\/code>\u5c31\u53ef\u4ee5\u4e86\uff0c\u800c\u975e\u975e\u5f97\u8fd4\u56de <code>=== true\/false<\/code>.<\/p>\n<p>\u56e0\u6b64\uff0c\u6211\u4eec\u5728\u4e3a\u4f4e\u7248\u672c\u6d4f\u89c8\u5668\u6269\u5c55\u65f6\u5019\uff0c\u65e0\u9700\u5173\u5fc3\u662f\u5426\u8fd4\u56de\u503c\u662f\u5426\u662f\u7eaf\u7cb9\u5e03\u5c14\u503c\uff08\u89c1\u4e0b\u9ed1\u8272\u4ee3\u7801\u90e8\u5206\uff09\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre>if (typeof Array.prototype.filter != \"function\") {\n  Array.prototype.filter = function (fn, context) {\n    var arr = [];\n    if (typeof fn === \"function\") {\n       for (var k = 0, length = this.length; k < length; k++) {\n          <span style=\"color:#000;\">fn.call(context, this[k], k, this)<\/span> &amp;&amp; arr.push(this[k]);\n       }\n    }\n    return arr;\n  };\n}<\/pre>\n<\/div>\n<p>\u63a5\u7740\u4e0a\u9762<code>map<\/code>\u7b5b\u9009\u90ae\u4ef6\u7684\u4f8b\u5b50\uff0c\u60a8\u53ef\u4ee5\u72e0\u72e0\u5730\u70b9\u51fb\u8fd9\u91cc\uff1a<a href=\"http:\/\/www.zhangxinxu.com\/study\/201304\/array-filter.html\" target=\"_blank\" class=\"a_link\">\u517c\u5bb9\u5904\u7406\u540efilter\u65b9\u6cd5\u6d4b\u8bd5demo<\/a><\/p>\n<p>\u4e3b\u8981\u6d4b\u8bd5\u4ee3\u7801\u4e3a\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre>var emailsZhang = users\n  <span class=\"comment\">\/\/ \u83b7\u5f97\u90ae\u4ef6<\/span>\n  .map(function (user) { return user.email; })\n  <span class=\"comment\">\/\/ \u7b5b\u9009\u51fazhang\u5f00\u5934\u7684\u90ae\u4ef6<\/span>\n  .filter(function(email) {  return \/^zhang\/.test(email); });\n\nconsole.log(emailsZhang.join(\", \")); <span class=\"comment\">\/\/ zhang@email.com<\/span><\/pre>\n<\/div>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/image.zhangxinxu.com\/image\/blog\/201304\/2013-04-25_140442.png\" width=\"215\" height=\"95\" alt=\"filter demo\u9875\u9762\u7684\u7ed3\u679c\u622a\u56fe \u5f20\u946b\u65ed-\u946b\u7a7a\u95f4-\u946b\u751f\u6d3b\" class=\"alignnone\" \/><\/p>\n<blockquote><p>\n\u5b9e\u9645\u4e0a\uff0c\u5b58\u5728\u4e00\u4e9b\u8bed\u6cd5\u7cd6\u53ef\u4ee5\u5b9e\u73b0<code>map+filter<\/code>\u7684\u6548\u679c\uff0c\u88ab\u79f0\u4e4b\u4e3a\u201c\u6570\u7ec4\u7b80\u7ea6\u5f0f(Array comprehensions)\u201d\u3002\u76ee\u524d\uff0c\u4ec5FireFox\u6d4f\u89c8\u5668\u53ef\u4ee5\u5b9e\u73b0\uff0c\u5c55\u793a\u4e0b\u53c8\u4e0d\u4f1a\u6000\u5b55\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre><span class=\"identifier\">var<\/span> <span class=\"constant\">zhangEmails<\/span> = [<span class=\"identifier\">user<\/span>.<span class=\"identifier\">email<\/span> <span class=\"identifier\"><span class=\"keyword\">for<\/span><\/span> <span class=\"identifier\"><span class=\"keymethods\">each<\/span><\/span> (<span class=\"identifier\">user<\/span> <span class=\"identifier\"><span class=\"keyword\">in<\/span><\/span> <span class=\"identifier\">users<\/span>) <span class=\"identifier\"><span class=\"keyword\">if<\/span><\/span> (<span class=\"regexp\">\/^zhang\/<\/span>.<span class=\"identifier\"><span class=\"keymethods\">test<\/span><\/span>(<span class=\"identifier\">user<\/span>.<span class=\"identifier\">email<\/span>)) ];\n\n<span class=\"identifier\">console.log<\/span>(<span class=\"constant\">zhangEmails<\/span>); <span class=\"comment\">\/\/ [zhang@email.com]<\/span><\/pre>\n<\/div>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/image.zhangxinxu.com\/image\/blog\/201304\/2013-04-25_141315.png\" width=\"578\" height=\"63\" alt=\"\u6570\u7ec4\u7b80\u7ea6\u5f0f(Array comprehensions)\u5b9e\u73b0\u7684map+filter\u6548\u679c\" class=\"alignnone\" \/>\n<\/p><\/blockquote>\n<\/li>\n<li><strong id=\"some\">some<\/strong><br \/>\n<code>some<\/code>\u610f\u6307\u201c\u67d0\u4e9b\u201d\uff0c\u6307\u662f\u5426\u201c\u67d0\u4e9b\u9879\u201d\u5408\u4e4e\u6761\u4ef6\u3002\u4e0e\u4e0b\u9762\u7684<code>every<\/code>\u7b97\u662f\u597d\u57fa\u53cb\uff0c<code>every<\/code>\u8868\u793a\u662f\u5426\u201c\u6bcf\u4e00\u9879\u201d\u90fd\u8981\u9760\u8c31\u3002\u7528\u6cd5\u5982\u4e0b\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre>array.some(callback,[ thisObject]);<\/pre>\n<\/div>\n<p>\u4f8b\u5982\u4e0b\u9762\u7684\u7b80\u5355\u4f7f\u7528\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre>var scores = [5, 8, 3, 10];\nvar current = 7;\n\nfunction higherThanCurrent(score) {\n  return score > current;\n}\n\nif (scores.some(higherThanCurrent)) {\n  alert(\"\u6715\u51c6\u4e86\uff01\");\n}<\/pre>\n<\/div>\n<p>\u7ed3\u679c\u5f39\u51fa\u4e86\u201c\u6715\u51c6\u4e86\u201d\u6587\u5b57\u3002 <code>some<\/code>\u8981\u6c42\u81f3\u5c11\u67091\u4e2a\u503c\u8ba9<code>callback<\/code>\u8fd4\u56de<code>true<\/code>\u5c31\u53ef\u4ee5\u4e86\u3002\u663e\u7136\uff0c<code>8 > 7<\/code>\uff0c\u56e0\u6b64<code>scores.some(higherThanCurrent)<\/code>\u503c\u4e3a<code>true<\/code>.<\/p>\n<p>\u6211\u4eec\u81ea\u7136\u53ef\u4ee5\u4f7f\u7528<code>forEach<\/code>\u8fdb\u884c\u5224\u65ad\uff0c\u4e0d\u8fc7\uff0c\u76f8\u6bd4<code>some<\/code>, \u4e0d\u8db3\u5728\u4e8e\uff0c<code>some<\/code>\u53ea\u6709\u6709<code>true<\/code>\u5373\u8fd4\u56de\u4e0d\u518d\u6267\u884c\u4e86\u3002<\/p>\n<p>IE6-IE8\u6269\u5c55\u5982\u4e0b\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre>if (typeof Array.prototype.some != \"function\") {\n  Array.prototype.some = function (fn, context) {\n\tvar passed = false;\n\tif (typeof fn === \"function\") {\n   \t  for (var k = 0, length = this.length; k < length; k++) {\n\t\t  if (passed === true) break;\n\t\t  passed = !!fn.call(context, this[k], k, this);\n\t  }\n    }\n\treturn passed;\n  };\n}<\/pre>\n<\/div>\n<p>\u4e8e\u662f\uff0c\u6211\u4eec\u5c31\u6709\u4e86\u201c\u6715\u51c6\u4e86\u201d\u7684demo\uff0c\u60a8\u53ef\u4ee5\u72e0\u72e0\u5730\u70b9\u51fb\u8fd9\u91cc\uff1a<a href=\"http:\/\/www.zhangxinxu.com\/study\/201304\/array-some.html\" target=\"_blank\" class=\"a_link\">\u517c\u5bb9\u5904\u7406\u540e\u7684some\u65b9\u6cd5demo<\/a><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/image.zhangxinxu.com\/image\/blog\/201304\/2013-04-25_160829.png\" width=\"306\" height=\"116\" alt=\"IE7\u6d4f\u89c8\u5668\u4e0bsome\u6269\u5c55demo\u7ed3\u679c\" class=\"alignnone\" \/>\n<\/li>\n<li><strong id=\"every\">every<\/strong><br \/>\n\u8ddf<code>some<\/code>\u7684\u57fa\u53cb\u5173\u7cfb\u5df2\u7ecf\u662f\u516c\u5f00\u7684\u79d8\u5bc6\u4e86\uff0c\u540c\u6837\u662f\u8fd4\u56deBoolean\u503c\uff0c\u4e0d\u8fc7\uff0c<code>every<\/code>\u9700\u8981\u6bcf\u4e00\u4e2a\u5983\u5b50\u90fd\u8981\u8ba9\u6715\u6ee1\u610f\uff0c\u5426\u5219\u2014\u2014\u201c\u6765\u4eba\uff0c\u7ed9\u6211\u62d6\u51fa\u53bb\u780d\u4e86\uff01\u201d<\/p>\n<p>IE6-IE8\u6269\u5c55\uff08\u4e0e<code>some<\/code>\u76f8\u6bd4\u5c31\u662f<code>true<\/code>\u548c<code>false<\/code>\u8c03\u6362\u4e00\u4e0b\uff09\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre>if (typeof Array.prototype.every != \"function\") {\n  Array.prototype.every = function (fn, context) {\n    var passed = true;\n    if (typeof fn === \"function\") {\n       for (var k = 0, length = this.length; k < length; k++) {\n          if (passed === false) break;\n          passed = !!fn.call(context, this[k], k, this);\n      }\n    }\n    return passed;\n  };\n}<\/pre>\n<\/div>\n<p>\u8fd8\u662f\u90a3\u4e2a\u6715\u7684\u4f8b\u5b50\uff0c\u60a8\u53ef\u4ee5\u72e0\u72e0\u5730\u70b9\u51fb\u8fd9\u91cc\uff1a<a href=\"http:\/\/www.zhangxinxu.com\/study\/201304\/array-every.html\" target=\"_blank\" class=\"a_link\">\u662f\u5426every\u5983\u5b50\u8ba9\u6715\u6ee1\u610fdemo<\/a><\/p>\n<div class=\"zxx_code\">\n<pre>if (scores.every(higherThanCurrent)) {\n  console.log(\"\u6715\u51c6\u4e86\uff01\");\n} else {\n  console.log(\"\u6765\u4eba\uff0c\u62d6\u51fa\u53bb\u65a9\u4e86\uff01\");        \n}<\/pre>\n<\/div>\n<p>\u7ed3\u679c\u662f\uff1a<br \/>\n<img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/image.zhangxinxu.com\/image\/blog\/201304\/2013-04-25_163305.png\" width=\"288\" height=\"94\" alt=\"every\u65b9\u6cd5\u7ed3\u679c\" class=\"alignnone\" \/>\n<\/li>\n<li><strong id=\"indexof\">indexOf<\/strong><br \/>\n<code>indexOf<\/code>\u65b9\u6cd5\u5728\u5b57\u7b26\u4e32\u4e2d\u81ea\u53e4\u5c31\u6709\uff0c<code>string.indexOf(searchString, position)<\/code>\u3002\u6570\u7ec4\u8fd9\u91cc\u7684<code>indexOf<\/code>\u65b9\u6cd5\u4e0e\u4e4b\u7c7b\u4f3c\u3002<\/p>\n<div class=\"zxx_code\">\n<pre>array.indexOf(searchElement[, fromIndex])<\/pre>\n<\/div>\n<p>\u8fd4\u56de\u6574\u6570\u7d22\u5f15\u503c\uff0c\u5982\u679c\u6ca1\u6709\u5339\u914d\uff08\u4e25\u683c\u5339\u914d\uff09\uff0c\u8fd4\u56de<code>-1<\/code>. <code>fromIndex<\/code>\u53ef\u9009\uff0c\u8868\u793a\u4ece\u8fd9\u4e2a\u4f4d\u7f6e\u5f00\u59cb\u641c\u7d22\uff0c\u82e5\u7f3a\u7701\u6216\u683c\u5f0f\u4e0d\u5408\u8981\u6c42\uff0c\u4f7f\u7528\u9ed8\u8ba4\u503c<code>0<\/code>\uff0c\u6211\u5728FireFox\u4e0b\u6d4b\u8bd5\uff0c\u53d1\u73b0\u4f7f\u7528\u5b57\u7b26\u4e32\u6570\u503c\u4e5f\u662f\u53ef\u4ee5\u7684\uff0c\u4f8b\u5982<code>\"3\"<\/code>\u548c<code>3<\/code>\u90fd\u53ef\u4ee5\u3002<\/p>\n<div class=\"zxx_code\">\n<pre>var data = [2, 5, 7, 3, 5];\n\nconsole.log(data.indexOf(5, \"x\")); <span class=\"comment\">\/\/ 1 (\"x\"\u88ab\u5ffd\u7565)<\/span>\nconsole.log(data.indexOf(5, \"3\")); <span class=\"comment\">\/\/ 4 (\u4ece3\u53f7\u4f4d\u5f00\u59cb\u641c\u7d22)<\/span>\n\nconsole.log(data.indexOf(4)); <span class=\"comment\">\/\/ -1 (\u672a\u627e\u5230)<\/span>\nconsole.log(data.indexOf(\"5\")); <span class=\"comment\">\/\/ -1 (\u672a\u627e\u5230\uff0c\u56e0\u4e3a5 !== \"5\")<\/span><\/pre>\n<\/div>\n<p>\u517c\u5bb9\u5904\u7406\u5982\u4e0b\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre>if (typeof Array.prototype.indexOf != \"function\") {\n  Array.prototype.indexOf = function (searchElement, fromIndex) {\n    var index = -1;\n    fromIndex = fromIndex * 1 || 0;\n\n    for (var k = 0, length = this.length; k < length; k++) {\n      if (k >= fromIndex && this[k] === searchElement) {\n          index = k;\n          break;\n      }\n    }\n    return index;\n  };\n}<\/pre>\n<\/div>\n<p>\u4e00\u4e2a\u8def\u5b50\u4e0b\u6765\u7684\uff0c\u663e\u7136\uff0c\u8f6e\u5230demo\u4e86\uff0c\u60a8\u53ef\u4ee5\u72e0\u72e0\u5730\u70b9\u51fb\u8fd9\u91cc\uff1a<a href=\"http:\/\/www.zhangxinxu.com\/study\/201304\/array-indexof.html\" target=\"_blank\" class=\"a_link\">\u517c\u5bb9\u5904\u7406\u540eindexOf\u65b9\u6cd5\u6d4b\u8bd5demo<\/a><\/p>\n<p>\u4e0b\u56fe\u4e3aietester IE6\u4e0b\u7684\u622a\u56fe\uff1a<br \/>\n<img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/image.zhangxinxu.com\/image\/blog\/201304\/2013-04-25_171244.png\" width=\"274\" height=\"143\" alt=\"IE6\u4e0bindexOf\u6269\u5c55\u540e\u6d4b\u8bd5\u7ed3\u679c\u622a\u56fe\" class=\"alignnone\" \/>\n<\/li>\n<li><strong id=\"lastindexof\">lastIndexOf<\/strong><br \/>\n<code>lastIndexOf<\/code>\u65b9\u6cd5\u4e0e<code>indexOf<\/code>\u65b9\u6cd5\u7c7b\u4f3c\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre>array.lastIndexOf(searchElement[, fromIndex])<\/pre>\n<\/div>\n<p>\u53ea\u662f<code>lastIndexOf<\/code>\u662f\u4ece\u5b57\u7b26\u4e32\u7684\u672b\u5c3e\u5f00\u59cb\u67e5\u627e\uff0c\u800c\u4e0d\u662f\u4ece\u5f00\u5934\u3002\u8fd8\u6709\u4e00\u4e2a\u4e0d\u540c\u5c31\u662f<code>fromIndex<\/code>\u7684\u9ed8\u8ba4\u503c\u662f<code>array.length - 1<\/code>\u800c\u4e0d\u662f<code>0<\/code>.<\/p>\n<p>IE6\u7b49\u6d4f\u89c8\u5668\u5982\u4e0b\u6298\u817e\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre>if (typeof Array.prototype.lastIndexOf != \"function\") {\n  Array.prototype.lastIndexOf = function (searchElement, fromIndex) {\n    var index = -1, length = this.length;\n    fromIndex = fromIndex * 1 || length - 1;\n\n    for (var k = length - 1; k > -1; k-=1) {\n        if (k <= fromIndex &amp;&amp; this[k] === searchElement) {\n            index = k;\n            break;\n        }\n    }\n    return index;\n  };\n}<\/pre>\n<\/div>\n<p>\u4e8e\u662f\uff0c\u5219\u6709\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre>var data = [2, 5, 7, 3, 5];\n\nconsole.log(data.lastIndexOf(5)); <span class=\"comment\">\/\/ 4<\/span>\nconsole.log(data.lastIndexOf(5, 3)); <span class=\"comment\">\/\/ 1 (\u4ece\u540e\u5f80\u524d\uff0c\u7d22\u5f15\u503c\u5c0f\u4e8e3\u7684\u5f00\u59cb\u641c\u7d22)<\/span>\n\nconsole.log(data.lastIndexOf(4)); <span class=\"comment\">\/\/ -1 (\u672a\u627e\u5230)<\/span><\/pre>\n<\/div>\n<p>\u61d2\u5f97\u622a\u56fe\u4e86\uff0c\u7ed3\u679c\u67e5\u770b\u53ef\u72e0\u72e0\u5730\u70b9\u51fb\u8fd9\u91cc\uff1a<a href=\"http:\/\/www.zhangxinxu.com\/study\/201304\/array-lastindexof.html\" target=\"_blank\" class=\"a_link\">lastIndexOf\u6d4b\u8bd5demo<\/a><\/p>\n<\/li>\n<li><strong id=\"reduce\">reduce<\/strong><br \/>\n<code>reduce<\/code>\u662fJavaScript 1.8\u4e2d\u624d\u5f15\u5165\u7684\uff0c\u4e2d\u6587\u610f\u601d\u4e3a\u201c\u51cf\u5c11\u201d\u3001\u201c\u7ea6\u7b80\u201d\u3002\u4e0d\u8fc7\uff0c\u4ece\u529f\u80fd\u6765\u770b\uff0c\u6211\u4e2a\u4eba\u662f\u65e0\u6cd5\u4e0e\u201c\u51cf\u5c11\u201d\u8fd9\u79cd\u542b\u4e49\u8054\u7cfb\u8d77\u6765\u7684\uff0c\u53cd\u800c\u66f4\u63a5\u8fd1\u4e8e\u201c\u8fed\u4ee3\u201d\u3001\u201c\u9012\u5f52(recursion)\u201d\uff0c\u64e6\uff0c\u56e0\u4e3a\u5355\u8bcd\u8fd9\u4e48\u63a5\u8fd1\uff0c\u4e0d\u4f1a\u662fECMA-262 5th\u5236\u5b9a\u8005\u7b14\u8bef\u5199\u9519\u4e86\u5427~~<img decoding=\"async\" src=\"http:\/\/mat1.gtimg.com\/www\/mb\/images\/face\/110.gif\" align=\"absmiddle\"><\/p>\n<p>\u6b64\u65b9\u6cd5\u76f8\u6bd4\u4e0a\u9762\u7684\u65b9\u6cd5\u90fd\u590d\u6742\uff0c\u7528\u6cd5\u5982\u4e0b\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre>array.reduce(callback[, initialValue])<\/pre>\n<\/div>\n<p><code>callback<\/code>\u51fd\u6570\u63a5\u53d74\u4e2a\u53c2\u6570\uff1a\u4e4b\u524d\u503c\u3001\u5f53\u524d\u503c\u3001\u7d22\u5f15\u503c\u4ee5\u53ca\u6570\u7ec4\u672c\u8eab\u3002<code>initialValue<\/code>\u53c2\u6570\u53ef\u9009\uff0c\u8868\u793a\u521d\u59cb\u503c\u3002\u82e5\u6307\u5b9a\uff0c\u5219\u5f53\u4f5c\u6700\u521d\u4f7f\u7528\u7684<code>previous<\/code>\u503c\uff1b\u5982\u679c\u7f3a\u7701\uff0c\u5219\u4f7f\u7528\u6570\u7ec4\u7684\u7b2c\u4e00\u4e2a\u5143\u7d20\u4f5c\u4e3a<code>previous<\/code>\u521d\u59cb\u503c\uff0c\u540c\u65f6<code>current<\/code>\u5f80\u540e\u6392\u4e00\u4f4d\uff0c\u76f8\u6bd4\u6709<code>initialValue<\/code>\u503c\u5c11\u4e00\u6b21\u8fed\u4ee3\u3002<\/p>\n<div class=\"zxx_code\">\n<pre>var sum = [1, 2, 3, 4].reduce(function (previous, current, index, array) {\n  return previous + current;\n});\n\nconsole.log(sum); <span class=\"comment\">\/\/ 10<\/span><\/pre>\n<\/div>\n<p>\u8bf4\u660e\uff1a<\/p>\n<ol>\n<li>\u56e0\u4e3a<code>initialValue<\/code>\u4e0d\u5b58\u5728\uff0c\u56e0\u6b64\u4e00\u5f00\u59cb\u7684<code>previous<\/code>\u503c\u7b49\u4e8e\u6570\u7ec4\u7684\u7b2c\u4e00\u4e2a\u5143\u7d20\u3002<\/li>\n<li>\u4ece\u800c<code>current<\/code>\u503c\u5728\u7b2c\u4e00\u6b21\u8c03\u7528\u7684\u65f6\u5019\u5c31\u662f<code>2<\/code>.<\/li>\n<li>\u6700\u540e\u4e24\u4e2a\u53c2\u6570\u4e3a\u7d22\u5f15\u503c<code>index<\/code>\u4ee5\u53ca\u6570\u7ec4\u672c\u8eab<code>array<\/code>.<\/li>\n<\/ol>\n<p>\u4ee5\u4e0b\u4e3a\u5faa\u73af\u6267\u884c\u8fc7\u7a0b\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre><span class=\"comment\">\/\/ \u521d\u59cb\u8bbe\u7f6e<\/span>\nprevious = initialValue = 1, current = 2\n\n<span class=\"comment\">\/\/ \u7b2c\u4e00\u6b21\u8fed\u4ee3<\/span>\nprevious = (1 + 2) =  3, current = 3\n\n<span class=\"comment\">\/\/ \u7b2c\u4e8c\u6b21\u8fed\u4ee3<\/span>\nprevious = (3 + 3) =  6, current = 4\n\n<span class=\"comment\">\/\/ \u7b2c\u4e09\u6b21\u8fed\u4ee3<\/span>\nprevious = (6 + 4) =  10, current = undefined (\u9000\u51fa)<\/pre>\n<\/div>\n<p>\u6709\u4e86<code>reduce<\/code>\uff0c\u6211\u4eec\u53ef\u4ee5\u8f7b\u677e\u5b9e\u73b0\u4e8c\u7ef4\u6570\u7ec4\u7684\u6241\u5e73\u5316\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre>var matrix = [\n  [1, 2],\n  [3, 4],\n  [5, 6]\n];\n\n<span class=\"comment\">\/\/ \u4e8c\u7ef4\u6570\u7ec4\u6241\u5e73\u5316<\/span>\nvar flatten = matrix.reduce(function (previous, current) {\n  return previous.concat(current);\n});\n\nconsole.log(flatten); <span class=\"comment\">\/\/ [1, 2, 3, 4, 5, 6]<\/span><\/pre>\n<\/div>\n<p>\u517c\u5bb9\u5904\u7406IE6-IE8\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre>if (typeof Array.prototype.reduce != \"function\") {\n  Array.prototype.reduce = function (callback, initialValue ) {\n     var previous = initialValue, k = 0, length = this.length;\n     if (typeof initialValue === \"undefined\") {\n        previous = this[0];\n        k = 1;\n     }\n     \n    if (typeof callback === \"function\") {\n      for (k; k < length; k++) {\n         this.hasOwnProperty(k) &#038;&#038; (previous = callback(previous, this[k], k, this));\n      }\n    }\n    return previous;\n  };\n}<\/pre>\n<\/div>\n<p>\u7136\u540e\uff0c\u6d4b\u8bd5\u6574\u5408\uff0cdemo\u6f14\u793a\uff0c\u60a8\u53ef\u4ee5\u72e0\u72e0\u5730\u70b9\u51fb\u8fd9\u91cc\uff1a<a href=\"http:\/\/www.zhangxinxu.com\/study\/201304\/array-reduce.html\" target=\"_blank\" class=\"a_link\">\u517c\u5bb9IE6\u7684reduce\u65b9\u6cd5\u6d4b\u8bd5demo<\/a><\/p>\n<p>IE6\u6d4f\u89c8\u5668\u4e0b\u7ed3\u679c\u5982\u4e0b\u56fe\uff1a<br \/>\n<img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/image.zhangxinxu.com\/image\/blog\/201304\/2013-04-25_191415.png\" width=\"244\" height=\"110\" alt=\"reduce\u65b9\u6cd5\u6d4b\u8bd5\u9875\u9762\u7ed3\u6784\u793a\u610f\" class=\"alignnone\" \/><\/p>\n<\/li>\n<li><strong id=\"reduceright\">reduceRight<\/strong><br \/>\n<code>reduceRight<\/code>\u8ddf<code>reduce<\/code>\u76f8\u6bd4\uff0c\u7528\u6cd5\u7c7b\u4f3c\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre>array.reduceRight(callback[, initialValue])<\/pre>\n<\/div>\n<p>\u5b9e\u73b0\u4e0a\u5dee\u5f02\u5728\u4e8e<code>reduceRight<\/code>\u662f\u4ece\u6570\u7ec4\u7684\u672b\u5c3e\u5f00\u59cb\u5b9e\u73b0\u3002\u770b\u4e0b\u9762\u8fd9\u4e2a\u4f8b\u5b50\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre>var data = [1, 2, 3, 4];\nvar specialDiff = data.reduceRight(function (previous, current, index) {\n  if (index == 0) {\n    return previous + current;\n  }\n  return previous - current;\n});\n\nconsole.log(specialDiff); <span class=\"comment\">\/\/ 0<\/span><\/pre>\n<\/div>\n<p>\u7ed3\u679c<code>0<\/code>\u662f\u5982\u4f55\u5f97\u5230\u7684\u5462\uff1f<br \/>\n\u6211\u4eec\u4e00\u6b65\u4e00\u6b65\u67e5\u770b\u5faa\u73af\u6267\u884c\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre><span class=\"comment\">\/\/ \u521d\u59cb\u8bbe\u7f6e<\/span>\nindex = 3, previous = initialValue = 4, current = 3\n\n<span class=\"comment\">\/\/ \u7b2c\u4e00\u6b21\u8fed\u4ee3<\/span>\nindex = 2, previous = (4- 3) = 1, current = 2\n\n<span class=\"comment\">\/\/ \u7b2c\u4e8c\u6b21\u8fed\u4ee3<\/span>\nindex = 1, previous = (1 - 2) = -1, current = 1\n\n<span class=\"comment\">\/\/ \u7b2c\u4e09\u6b21\u8fed\u4ee3<\/span>\nindex = 0, previous = (-1 + 1) = 0, current = undefined (\u9000\u51fa)<\/pre>\n<\/div>\n<p>\u4e3a\u4f7f\u4f4e\u7248\u672c\u6d4f\u89c8\u5668\u652f\u6301\u6b64\u65b9\u6cd5\uff0c\u60a8\u53ef\u4ee5\u6dfb\u52a0\u5982\u4e0b\u4ee3\u7801\uff1a<\/p>\n<div class=\"zxx_code\">\n<pre>if (typeof Array.prototype.reduceRight != \"function\") {\n  Array.prototype.reduceRight = function (callback, initialValue ) {\n    var length = this.length, k = length - 1, previous = initialValue;\n    if (typeof initialValue === \"undefined\") {\n        previous = this[length - 1];\n        k--;\n    }\n    if (typeof callback === \"function\") {\n       for (k; k > -1; k-=1) {          \n          this.hasOwnProperty(k) && (previous = callback(previous, this[k], k, this));\n       }\n    }\n    return previous;\n  };\n}<\/pre>\n<\/div>\n<p>\u60a8\u53ef\u4ee5\u72e0\u72e0\u5730\u70b9\u51fb\u8fd9\u91cc\uff1a<a href=\"http:\/\/www.zhangxinxu.com\/study\/201304\/array-reduceright.html\" target=\"_blank\" class=\"a_link\">reduceRight\u7b80\u5355\u4f7f\u7528demo<\/a><\/p>\n<p>\u5bf9\u6bd4FireFox\u6d4f\u89c8\u5668\u548cIE7\u6d4f\u89c8\u5668\u4e0b\u7684\u7ed3\u679c\uff1a<br \/>\n<img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/image.zhangxinxu.com\/image\/blog\/201304\/2013-04-25_205011.png\" width=\"403\" height=\"168\" alt=\"FireFox\u6d4f\u89c8\u5668\u4e0breduceRight\u6d4b\u8bd5\u7ed3\u679c\" class=\"alignnone\" \/> <img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/image.zhangxinxu.com\/image\/blog\/201304\/2013-04-25_205035.png\" width=\"408\" height=\"174\" alt=\"\u5bf9\u6bd4IE7\u4e0breduceRight\u6d4b\u8bd5\u7ed3\u679c\u622a\u56fe \u5f20\u946b\u65ed-\u946b\u7a7a\u95f4-\u946b\u751f\u6d3b\" class=\"alignnone\" \/>\n<\/li>\n<\/ol>\n<h3>\u4e09\u3001\u66f4\u8fdb\u4e00\u6b65\u7684\u5e94\u7528<\/h3>\n<p>\u6211\u4eec\u8fd8\u53ef\u4ee5\u5c06\u4e0a\u9762\u8fd9\u4e9b\u6570\u7ec4\u65b9\u6cd5\u5e94\u7528\u5728\u5176\u4ed6\u5bf9\u8c61\u4e0a\u3002<\/p>\n<p>\u4f8b\u5982\uff0c\u6211\u4eec\u4f7f\u7528forEach\u904d\u5386DOM\u5143\u7d20\u3002<\/p>\n<div class=\"zxx_code\">\n<pre>var eleDivs = document.getElementsByTagName(\"div\");\nArray.prototype.forEach.call(eleDivs, function(div) {\n    console.log(\"\u8be5div\u7c7b\u540d\u662f\uff1a\" + (div.className || \"\u7a7a\"));\n});<\/pre>\n<\/div>\n<p>\u53ef\u4ee5\u8f93\u51fa\u9875\u9762\u6240\u6709<code>div<\/code>\u7684\u7c7b\u540d\uff0c\u60a8\u53ef\u4ee5\u72e0\u72e0\u5730\u70b9\u51fb\u8fd9\u91cc\uff1a<a href=\"http:\/\/www.zhangxinxu.com\/study\/201304\/array-foreach-dom-loop.html\" target=\"_blank\" class=\"a_link\">Array\u65b0\u65b9\u6cd5forEach\u904d\u5386DOM demo<\/a><\/p>\n<p>\u7ed3\u679c\u5982\u4e0b\uff0cIE6\u4e0b\uff0cdemo\u7ed3\u679c\uff1a<br \/>\n<img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/image.zhangxinxu.com\/image\/blog\/201304\/2013-04-25_213419.png\" width=\"362\" height=\"239\" alt=\"forEach\u65b9\u6cd5\u904d\u5386DOM\u7684\u4f7f\u7528\u6f14\u793a \u5f20\u946b\u65ed-\u946b\u7a7a\u95f4-\u946b\u751f\u6d3b\" class=\"alignnone\" \/><\/p>\n<p>\u7b49\u5f88\u591a\u5176\u4ed6\u7c7b\u6570\u7ec4\u5e94\u7528\u3002<\/p>\n<h3>\u56db\u3001\u6700\u540e\u4e00\u70b9\u70b9\u4e86<\/h3>\n<p>\u672c\u6587\u4e3a\u4f4e\u7248\u672cIE\u6269\u5c55\u7684Array\u65b9\u6cd5\u6211\u90fd\u5408\u5e76\u5230\u4e00\u4e2aJS\u4e2d\u4e86\uff0c\u60a8\u53ef\u4ee5\u8f7b\u8f7b\u7684\u53f3\u952e\u8fd9\u91cc\u6216\u4e0b\u8f7d\u6216\u67e5\u770b\uff1a<a href=\"http:\/\/www.zhangxinxu.com\/study\/201304\/es5-array.js\" target=\"_blank\" class=\"a_link\">es5-array.js<\/a><\/p>\n<p>\u4ee5\u4e0a\u6240\u6709\u672aIE\u6269\u5c55\u7684\u65b9\u6cd5\u90fd\u662f\u81ea\u5df1\u6839\u636e\u7406\u89e3\u5199\u7684\uff0c\u867d\u7136\u591a\u756a\u6d4b\u8bd5\uff0c\u96be\u514d\u8fd8\u4f1a\u6709\u7ec6\u8282\u9057\u6f0f\u7684\uff0c\u6b22\u8fce\u6307\u51fa\u6765\u3002<\/p>\n<p><strong>\u53c2\u8003\u6587\u7ae0\uff1a<\/strong><br \/>\n<a href=\"http:\/\/dev.opera.com\/articles\/view\/javascript-array-extras-in-detail\/\">JavaScript array \u201cextras\u201d in detail<\/a><br \/>\n<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/JavaScript\/Reference\/Global_Objects\/Array\/forEach\">Array.forEach<\/a><\/p>\n<p>\u672c\u6587\u4e3a\u539f\u521b\u6587\u7ae0\uff0c\u8f6c\u8f7d\u8bf7\u6ce8\u660e\u6765\u81ea<a href=\"http:\/\/www.zhangxinxu.com\/\">\u5f20\u946b\u65ed-\u946b\u7a7a\u95f4-\u946b\u751f\u6d3b<\/a>[<a href=\"http:\/\/www.zhangxinxu.com\/\">http:\/\/www.zhangxinxu.com<\/a>]<br \/>\n\u672c\u6587\u5730\u5740\uff1a<a href=\"http:\/\/www.zhangxinxu.com\/wordpress\/?p=3220\">http:\/\/www.zhangxinxu.com\/wordpress\/?p=3220<\/a><\/p>\n<p>\uff08\u672c\u7bc7\u5b8c\uff09<\/p>\n","protected":false},"excerpt":{"rendered":"<p>ES5\u4e2d\u65b0\u589e\u7684\u4e0d\u5c11\u4e1c\u897f\uff0c\u4e86\u89e3\u4e4b\u5bf9\u6211\u4eec\u5199JavaScript\u4f1a\u6709\u4e0d\u5c11\u5e2e\u52a9\uff0c\u6bd4\u5982\u6570\u7ec4\u8fd9\u5757\uff0c\u6211\u4eec\u53ef\u80fd\u5c31\u4e0d\u9700\u8981\u53bb\u6709\u677f\u6709\u773c\u5730<code>for<\/code>\u5faa\u73af\u4e86\u3002<br \/>\nES5\u4e2d\u65b0\u589e\u4e86\u5199\u6570\u7ec4\u65b9\u6cd5\uff0c\u5982\u4e0b\uff1a<code>forEach<\/code>, <code>map<\/code>, <code>filte<\/code>r, <code>some<\/code>, <code>every<\/code>, <code>indexOf<\/code>, <code>lastIndexOf<\/code>, <code>reduce<\/code>, <code>reduceRight<\/code> \u2026\u2026<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[180],"tags":[668,797,368,794,795,801,800,798,799,796,669],"_links":{"self":[{"href":"https:\/\/www.zhangxinxu.com\/wordpress\/wp-json\/wp\/v2\/posts\/3220"}],"collection":[{"href":"https:\/\/www.zhangxinxu.com\/wordpress\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.zhangxinxu.com\/wordpress\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.zhangxinxu.com\/wordpress\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.zhangxinxu.com\/wordpress\/wp-json\/wp\/v2\/comments?post=3220"}],"version-history":[{"count":0,"href":"https:\/\/www.zhangxinxu.com\/wordpress\/wp-json\/wp\/v2\/posts\/3220\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.zhangxinxu.com\/wordpress\/wp-json\/wp\/v2\/media?parent=3220"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.zhangxinxu.com\/wordpress\/wp-json\/wp\/v2\/categories?post=3220"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.zhangxinxu.com\/wordpress\/wp-json\/wp\/v2\/tags?post=3220"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}