{"id":356,"date":"2019-01-04T01:49:06","date_gmt":"2019-01-03T17:49:06","guid":{"rendered":"https:\/\/wp.winter-weng.cc\/work\/?p=356"},"modified":"2019-01-04T01:49:06","modified_gmt":"2019-01-03T17:49:06","slug":"ch-8-%e7%89%a9%e4%bb%b6","status":"publish","type":"post","link":"https:\/\/wp.winter-weng.cc\/work\/?p=356","title":{"rendered":"Ch. 8 \u7269\u4ef6"},"content":{"rendered":"<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_75 counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Table of Contents<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"\u986f\u793a\/\u96b1\u85cf\u5167\u5bb9\u76ee\u9304\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/wp.winter-weng.cc\/work\/?p=356\/#%E8%AA%9E%E6%B3%95\" >\u8a9e\u6cd5<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/wp.winter-weng.cc\/work\/?p=356\/#%E5%9E%8B%E5%88%A5\" >\u578b\u5225<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/wp.winter-weng.cc\/work\/?p=356\/#%E5%85%A7%E5%BB%BA%E7%89%A9%E4%BB%B6\" >\u5167\u5efa\u7269\u4ef6<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/wp.winter-weng.cc\/work\/?p=356\/#%E5%85%A7%E5%AE%B9\" >\u5167\u5bb9<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/wp.winter-weng.cc\/work\/?p=356\/#%E8%A8%88%E7%AE%97%E5%BE%97%E5%87%BA%E7%9A%84%E7%89%B9%E6%80%A7%E5%90%8D%E7%A8%B1\" >\u8a08\u7b97\u5f97\u51fa\u7684\u7279\u6027\u540d\u7a31<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/wp.winter-weng.cc\/work\/?p=356\/#%E7%89%B9%E6%80%A7_vs_%E6%96%B9%E6%B3%95\" >\u7279\u6027 vs. \u65b9\u6cd5<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/wp.winter-weng.cc\/work\/?p=356\/#%E9%99%A3%E5%88%97\" >\u9663\u5217<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/wp.winter-weng.cc\/work\/?p=356\/#%E8%A4%87%E8%A3%BD%E7%89%A9%E4%BB%B6\" >\u8907\u88fd\u7269\u4ef6<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"https:\/\/wp.winter-weng.cc\/work\/?p=356\/#%E7%89%B9%E6%80%A7%E6%8F%8F%E8%BF%B0%E5%99%A8\" >\u7279\u6027\u63cf\u8ff0\u5668<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-10\" href=\"https:\/\/wp.winter-weng.cc\/work\/?p=356\/#%E4%B8%8D%E5%8F%AF%E8%AE%8A%E6%80%A7\" >\u4e0d\u53ef\u8b8a\u6027<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-11\" href=\"https:\/\/wp.winter-weng.cc\/work\/?p=356\/#Get\" >[[Get]]<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-12\" href=\"https:\/\/wp.winter-weng.cc\/work\/?p=356\/#Put\" >[[Put]]<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-13\" href=\"https:\/\/wp.winter-weng.cc\/work\/?p=356\/#getter_%E8%88%87_setter\" >getter \u8207 setter<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-14\" href=\"https:\/\/wp.winter-weng.cc\/work\/?p=356\/#%E5%AD%98%E5%9C%A8\" >\u5b58\u5728<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-15\" href=\"https:\/\/wp.winter-weng.cc\/work\/?p=356\/#%E5%88%97%E8%88%89\" >\u5217\u8209<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-16\" href=\"https:\/\/wp.winter-weng.cc\/work\/?p=356\/#%E8%BF%AD%E4%BB%A3\" >\u8fed\u4ee3<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-17\" href=\"https:\/\/wp.winter-weng.cc\/work\/?p=356\/#%E8%A4%87%E7%BF%92\" >\u8907\u7fd2<\/a><\/li><\/ul><\/nav><\/div>\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E8%AA%9E%E6%B3%95\"><\/span><strong>\u8a9e\u6cd5<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n<p>\u5ba3\u544a\u5f0f (declarative)\u3001\u5b57\u9762\u503c (literal)\uff1a<\/p>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"js\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"true\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">var myObj = {\n\tkey: value;\n}<\/pre>\n\n\n<p>\u5efa\u69cb\u5f0f (constructed form)\uff1a<\/p>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"js\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"true\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">var myObj = new Object();\nmyObj.key = value;<\/pre>\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E5%9E%8B%E5%88%A5\"><\/span><strong>\u578b\u5225<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n<ul class=\"wp-block-list\"><li>\u516d\u7a2e\u578b\u5225\uff1astring\u3001number\u3001boolean\u3001null\u3001undefined\u3001object<\/li><li>null \u4e0d\u662f object<\/li><\/ul>\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E5%85%A7%E5%BB%BA%E7%89%A9%E4%BB%B6\"><\/span>\u5167\u5efa\u7269\u4ef6<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n<p>string\u3001number\u3001boolean\u3001object\u3001function\u3001Array\u3001Date\u3001RegExp\u3001Error<br \/>\u9019\u4e9b\u5176\u5be6\u662f\u5167\u5efa\u7684\u51fd\u5f0f\uff0c\u53ef\u4ee5\u88ab\u4f5c\u70ba\u5efa\u69cb\u5668\u642d\u914d new \u4f86\u547c\u53eb\u3002<\/p>\n\n\n<p>\u57fa\u672c\u578b\u5225\u503c (eg. <code>var str = \"I am a string\";<\/code>) \u4e26\u4e0d\u662f\u4e00\u500b\u7269\u4ef6\uff0c\u7576\u5728\u4e0a\u9762\u9032\u884c\u64cd\u4f5c (\u5982\u53d6\u5f97\u9577\u5ea6\u3001\u5b58\u53d6\u500b\u5225\u5b57\u5143\u7b49) \u6642 JS \u6703\u5c07\u5176<strong>\u5f37\u5236\u8f49\u578b<\/strong>\u70ba\u4e00\u500b\u7269\u4ef6\u3002<\/p>\n\n\n<ul class=\"wp-block-list\"><li>null \u8207 undefined \u6c92\u6709\u7269\u4ef6\u5305\u88f9\u5668\u7684\u5f62\u5f0f\u3002<\/li><li>Date \u6c92\u6709\u5c0d\u61c9\u7684\u5b57\u9762\u503c\u5f62\u5f0f\u3002<\/li><li>object\u3001function\u3001Array\u3001RegExp \u7fd2\u6163\u4e0a\u4f7f\u7528\u7c21\u4fbf\u7684\u5b57\u9762\u503c\u5f62\u5f0f\uff0c\u9664\u975e\u9700\u8981\u984d\u5916\u7684\u8a2d\u5b9a\u6642\uff0c\u624d\u4f7f\u7528\u5efa\u69cb\u5f62\u5f0f\u3002<\/li><li>Error \u6703\u5728\u88ab\u64f2\u51fa\u6642\u81ea\u52d5\u88ab\u5275\u5efa\u3002<\/li><\/ul>\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E5%85%A7%E5%AE%B9\"><\/span><strong>\u5167\u5bb9<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n<p>\u7269\u4ef6\u7684\u5167\u5bb9\u7531\u4efb\u610f\u578b\u5225\u7684\u503c (values) \u6240\u69cb\u6210\uff0c\u503c\u88ab\u5132\u5b58\u5728\u547d\u540d\u904e\u7684\u4f4d\u7f6e\u4e2d\uff0c\u7a31\u4e4b\u70ba\u7279\u6027 (properties)\u3002\u7269\u4ef6\u5167\u5bb9\u4e2d\u53ea\u6703\u5132\u5b58\u7279\u6027\u540d\u7a31 (property names)\uff0c\u540d\u7a31\u6307\u5411\u503c\u5132\u5b58\u4e4b\u8655 (references)\u3002<\/p>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"js\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"true\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">var myObj = {\n\ta: 2\n};\nmyObj.a;    \/\/ \u7279\u6027\u5b58\u53d6\nmyObj[\"a\"]; \/\/ \u9375\u503c\u5b58\u53d6\uff0c\u53ef\u63a5\u53d7\u4efb\u4f55\u76f8\u5bb9\u65bc Unicode \u7684\u5b57\u4e32<\/pre>\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E8%A8%88%E7%AE%97%E5%BE%97%E5%87%BA%E7%9A%84%E7%89%B9%E6%80%A7%E5%90%8D%E7%A8%B1\"><\/span>\u8a08\u7b97\u5f97\u51fa\u7684\u7279\u6027\u540d\u7a31<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n<p>ES6 \u65b0\u589e computed property names\u3002\u53ef\u4ee5\u5728\u7269\u4ef6\u7684 key \u4e2d\u4f7f\u7528\u904b\u7b97\u5f0f\u3002<\/p>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"js\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"true\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">var prefix = \"foo\";\nvar myObject = {\n\t[prefix + \"bar\"]: \"hello\",\n\t[prefix + \"baz\"]: \"world\"\n};\nmyObject[\"foobar\"]; \/\/ hello\nmyObject[\"foobaz\"]; \/\/ world<\/pre>\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E7%89%B9%E6%80%A7_vs_%E6%96%B9%E6%B3%95\"><\/span>\u7279\u6027 vs. \u65b9\u6cd5<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n<p>\u5728\u5176\u4ed6\u8a9e\u8a00\u4e2d\uff0c\u5c6c\u65bc\u7269\u4ef6 (\u6216\u985e\u5225\uff0cclass) \u7684\u51fd\u5f0f\uff0c\u88ab\u7a31\u4e4b\u70ba\u65b9\u6cd5 (method)\u3002<br \/>\u7136\u800c\uff0c\u5728 JS \u4e2d\uff0c\u51fd\u5f0f\u6c38\u9060\u4e0d\u6703\u5c6c\u65bc\u7269\u4ef6\uff0c\u5728\u7269\u4ef6\u4e2d\u6240\u5ba3\u544a\u7684\u51fd\u5f0f\u4e5f\u53ea\u662f\u5c0d\u65bc\u51fd\u5f0f\u7684\u53c3\u8003\u4e4b\u4e00\u3002<\/p>\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E9%99%A3%E5%88%97\"><\/span>\u9663\u5217<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n<ul class=\"wp-block-list\"><li>\u9663\u5217\u9810\u8a2d\u4f7f\u7528\u6578\u503c\u7d22\u5f15\uff0c\u4ee5\u975e\u8ca0\u6574\u6578\u4f86\u7de8\u865f\u3002<\/li><li>\u9663\u5217\u662f\u4e00\u500b\u7269\u4ef6\uff0c\u5373\u4f7f\u7d22\u5f15\u503c\u4e0d\u662f\u975e\u8ca0\u6574\u6578\uff0c\u4ecd\u7136\u53ef\u4ee5\u65b0\u589e\uff0c\u4f46\u9663\u5217\u7684\u9577\u5ea6\u5c07\u4e0d\u6703\u8a08\u7b97\u3002<\/li><li><strong>\u770b\u8d77\u4f86\u50cf\u6578\u5b57<\/strong>\u7684\u7d22\u5f15\u503c\u6703\u88ab\u8f49\u578b\u3002<\/li><\/ul>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"js\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"true\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">var myArray = [ \"foo\", 42, \"bar\" ];\nmyArray.baz = \"baz\";\nmyArray.length;  \/\/ 3\nmyArray.baz;     \/\/ \"baz\"\nmyArray[\"3\"] = \"baz\";\nmyArray.length;  \/\/ 4\nmyArray[3];      \/\/ \"baz\"<\/pre>\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E8%A4%87%E8%A3%BD%E7%89%A9%E4%BB%B6\"><\/span>\u8907\u88fd\u7269\u4ef6<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n<p>\u6dfa\u5c64\u62f7\u8c9d (shallow) \uff1a\u57fa\u672c\u578b\u5225\u503c\u70ba\u8907\u88fd\u54c1\uff0c\u7269\u4ef6\u5247\u662f\u6307\u5411\u76f8\u540c\u7684\u53c3\u8003\u3002<br \/>\u6df1\u5c64\u62f7\u8c9d (deep)\uff1a\u8907\u88fd\u6240\u6709\u7684\u5167\u5bb9\u3002<\/p>\n\n\n<p>\u5fae\u5999\u7684\u89e3\u6cd5\uff0c\u5c07\u7269\u4ef6\u5e8f\u5217\u5316\u6210 JSON \u5b57\u4e32\u3002<\/p>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"js\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"true\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">var newObj = JSON.parse( JSON.stringify( someObj ) );<\/pre>\n\n\n<p>ES6 \u63d0\u4f9b\u4e86 <code>Object.assign(target, ...source object)<\/code>\uff0c\u5b83\u6703\u8fed\u4ee3\u6240\u6709\u53ef\u5217\u8209\u7684 (enumerable)\u3001\u81ea\u6709\u7684 (owned) \u9375\u503c\uff0c\u4e26\u5c07\u5b83\u5011\u8907\u88fd\u5230\u76ee\u6a19\u4e0a\u3002<\/p>\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E7%89%B9%E6%80%A7%E6%8F%8F%E8%BF%B0%E5%99%A8\"><\/span>\u7279\u6027\u63cf\u8ff0\u5668<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n<p>\u5728 ES5 \u4e2d\uff0c\u6240\u6709\u7279\u6027\u90fd\u6703\u4ee5\u7279\u6027\u63cf\u8ff0\u5668 (property descriptor) \u4f86\u52a0\u4ee5\u63cf\u8ff0\u3002<\/p>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"js\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"true\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">var myObject = {\n\ta: 2\n};\nObject.getOwnPropertyDescriptor( myObject, \"a\" );\n\/\/ {\n\/\/    value: 2,\n\/\/    writable: true,\n\/\/    enumerable: true,\n\/\/    configurable: true\n\/\/ }<\/pre>\n\n\n<p>\u6211\u5011\u4e5f\u53ef\u4ee5\u4f7f\u7528 <code>Object.defineProperty(..)<\/code> \u4f86\u65b0\u589e\u6216\u4fee\u6539\u4e00\u500b\u7279\u6027\u3002<\/p>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"js\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">var myObject = {};\nObject.defineProperty( myObject, \"a\", {\n\tvalue: 2,\n\twritable: true,\n\tconfigurable: true,\n\tenumerable: true\n} );\nmyObject.a;  \/\/ 2<\/pre>\n\n\n<ul><li>writable\uff1a\u662f\u5426\u80fd\u5920\u6539\u8b8a\u4e00\u500b\u7279\u6027\u7684\u503c\u3002<\/li><li>configurable\uff1a\u662f\u5426\u80fd\u4f7f\u7528 <code>Object.defineProperty(..)<\/code> \u4fee\u6539\u63cf\u8ff0\u5668\u5b9a\u7fa9\u3002<br \/>\u7576 configurable \u70ba false \u6642\uff1a<br \/>1. writable \u9084\u662f\u53ef\u4ee5\u5f9e true \u88ab\u6539\u70ba false\uff1b<br \/>2. \u7981\u6b62\u4f7f\u7528 delete \u522a\u9664\u7279\u6027\u3002<\/li><li>enumerable\uff1a\u662f\u5426\u70ba\u53ef\u5217\u8209\u7684\u3002\u57f7\u884c <code>for..in<\/code> \u6216 <code>Object.keys(..)<\/code> \u7b49\u5217\u8209\u52d5\u4f5c\u6642\uff0c\u8a72\u7279\u6027\u5c07\u4e0d\u6703\u51fa\u73fe\u3002<\/li><\/ul>\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E4%B8%8D%E5%8F%AF%E8%AE%8A%E6%80%A7\"><\/span>\u4e0d\u53ef\u8b8a\u6027<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n<ul class=\"wp-block-list\"><li>\u7269\u4ef6\u5e38\u6578\uff1a\u4f7f\u7528 <code>writable: false<\/code> \u548c <code>configurable: false<\/code> \u80fd\u5efa\u7acb\u51fa\u7121\u6cd5\u88ab\u8b8a\u66f4\u3001\u4e0d\u53ef\u91cd\u5b9a\u7fa9\u3001\u4e0d\u53ef\u522a\u9664\u7684\u5e38\u6578\u3002<\/li><li>\u907f\u514d\u64f4\u5145\uff1a\u547c\u53eb <code>Object.preventExtensions(..)<\/code> \u53ef\u9632\u6b62\u65b0\u7684\u7279\u6027\u88ab\u52a0\u5230\u7269\u4ef6\u4e0a\u3002 <\/li><li>\u5bc6\u5c01\uff1a<code>Object.seal(..)<\/code> = \u907f\u514d\u64f4\u5145 + <code>configurable: false<\/code>\uff0c\u4e0d\u53ef\u65b0\u589e\u3001\u4e0d\u53ef\u91cd\u65b0\u914d\u7f6e\u6216\u522a\u9664\u3002<\/li><li>\u51cd\u7d50\uff1a<code>Object.freeze(..)<\/code> = \u5bc6\u5c01 + <code>writable: false<\/code>\uff0c\u4e0d\u53ef\u65b0\u589e\u3001\u4e0d\u53ef\u91cd\u65b0\u914d\u7f6e\u6216\u522a\u9664\uff0c\u4e26\u4e14\u4e0d\u53ef\u66f4\u6539\u503c\u3002<\/li><\/ul>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"js\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"true\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/ Object.preventExtensions(..)\nvar myObject = {\n\ta: 2\n};\nObject.preventExtensions( myObject );\nmyObject.b = 3;\nmyObject.b; \/\/ undefined<\/pre>\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Get\"><\/span>[[Get]]<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n<p>\u7279\u6027\u5b58\u53d6\u4e0d\u53ea\u6703\u5728\u7269\u4ef6\u4e2d\u5c0b\u627e\u7279\u6027\uff0c\u9084\u6703\u5de1\u8a2a [[Prototype]] \u4e32\u93c8\uff0c\u5982\u679c\u7121\u6cd5\u85c9\u7531\u4efb\u4f55\u65b9\u6cd5\u627e\u5230\u8a72\u7279\u6027\uff0c\u6703\u56de\u50b3 undefined\u3002<\/p>\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Put\"><\/span>[[Put]]<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n<p>\u6f14\u7b97\u6cd5\u6703\u5927\u81f4\u6aa2\u67e5\uff1a<\/p>\n\n\n<ol class=\"wp-block-list\"><li>\u8a72\u7279\u6027\u662f\u4e00\u500b\u5b58\u53d6\u5668\u63cf\u8ff0\u5668\u55ce\uff1f\u82e5\u662f\uff0c\u5c31\u547c\u53eb Setter\u3002<\/li><li>\u8a72\u7279\u6027\u662f writable \u70ba false \u7684\u8cc7\u6599\u63cf\u8ff0\u5668\u55ce\uff1f\u82e5\u662f\uff0c\u5c31\u6703\u8a2d\u503c\u5931\u6557\u3002<\/li><li>\u5426\u5247\uff0c\u6309\u7167\u6b63\u5e38\u65b9\u5f0f\u5c07\u503c\u8a2d\u5b9a\u7d66\u7279\u6027\u3002<\/li><\/ol>\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"getter_%E8%88%87_setter\"><\/span>getter \u8207 setter<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n<p>[[Get]] \u8207 [[Put]] \u63a7\u5236\u4e86\u503c\u5982\u4f55\u88ab\u8a2d\u5b9a\u548c\u53d6\u5f97\u7684\u9810\u8a2d\u884c\u70ba\uff0c\u5982\u679c\u8981\u8986\u5beb\u9019\u4e9b\u884c\u70ba\uff0c\u53ef\u4ee5\u900f\u904e\u5b9a\u7fa9 getter \u6216 setter \u4f86\u9054\u6210\u3002<\/p>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"js\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"true\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">var myObject = {\n\t\/\/ define a getter for `a`\n\tget a() {\n\t\treturn this._a_;\n\t},\n\t\/\/ define a setter for `a`\n\tset a(val) {\n\t\tthis._a_ = val * 2;\n\t}\n};\nmyObject.a = 2;\nmyObject.a; \/\/ 4<\/pre>\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E5%AD%98%E5%9C%A8\"><\/span>\u5b58\u5728<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n<p>\u8a62\u554f\u7269\u4ef6\u662f\u5426\u64c1\u6709\u67d0\u500b\u7279\u6027\uff0c<code>in<\/code> \u6703\u5bdf\u770b\u7279\u6027\u540d\u7a31\u662f\u5426\u5728\u7269\u4ef6\u4e2d\uff0c\u6216\u662f\u66f4\u9ad8\u5c64\u7684 [[Prototype]] \u4e32\u93c8\uff1b<code>hasOwnProperty(..)<\/code> \u53ea\u6703\u6aa2\u67e5\u8a72\u7269\u4ef6\u3002<br \/><\/p>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"js\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"true\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">var myObject = {\n\ta: 2\n};\n(\"a\" in myObject);    \/\/ true\n(\"b\" in myObject);    \/\/ false\nmyObject.hasOwnProperty( \"a\" );    \/\/ true\nmyObject.hasOwnProperty( \"b\" );    \/\/ false<\/pre>\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E5%88%97%E8%88%89\"><\/span>\u5217\u8209<span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n<ul class=\"wp-block-list\"><li><code>propertyIsEnumerable(..)<\/code>  \u6703\u6e2c\u8a66\u7d66\u5b9a\u7684\u7279\u6027\u540d\u7a31\u662f\u5426\u76f4\u63a5\u5b58\u5728\u65bc\u7269\u4ef6\u4e0a\uff0c\u4e26\u4e14\u662f\u53ef\u5217\u8209\u7684 (<code>enumerable: true<\/code>)\u3002<\/li><li><code>Object.keys(..)<\/code>  \u56de\u50b3<strong>\u6240\u6709\u53ef\u5217\u8209\u7279\u6027<\/strong>\u6240\u69cb\u6210\u7684\u9663\u5217\u3002<\/li><li><code>Object.getOwnPropertyNames(..)<\/code>  \u56de\u50b3<strong>\u6240\u6709\u7279\u6027<\/strong>\u69cb\u6210\u7684\u9663\u5217\u3002<\/li><li>\u4e0a\u8ff0\u5169\u500b\u65b9\u6cd5\u90fd\u53ea\u6703\u5de1\u5217\u7d66\u5b9a\u7684\u7269\u4ef6\u3002<\/li><\/ul>\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E8%BF%AD%E4%BB%A3\"><\/span><strong>\u8fed\u4ee3<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n<p>ES5\/ES6 \u63d0\u4f9b\u4e86\u591a\u500b\u9663\u5217\u8fed\u4ee3\u8f14\u52a9\u5668\uff0c\u5982<\/p>\n\n\n<ul class=\"wp-block-list\"><li>Array.forEach(..)\uff1a\u8fed\u4ee3\u9663\u5217\u4e2d\u7684\u6240\u6709\u503c\u3002<\/li><li>Array.every(..)\uff1a\u8fed\u4ee3\u6240\u6709\u503c\uff0c\u76f4\u5230 callback \u56de\u50b3\u4e00\u500b false\u3002<\/li><li>Array.some(..)\uff1a\u8fed\u4ee3\u6240\u6709\u503c\uff0c\u76f4\u5230 callback \u56de\u50b3\u4e00\u500b true\u3002<\/li><li>for..of (ES6)\uff1a\u76f4\u63a5\u8fed\u4ee3\u9663\u5217\u4e2d\u7684\u503c\u3002<\/li><\/ul>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"js\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"true\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/ Array.some(..)\nconst list = [\n  {\n    name: 'Winter',\n    age: 20,\n  },\n  {\n    name: 'Jeff',\n    age: 28,\n  },\n  {\n    name: 'Cindy',\n    age: 13,\n  },\n];\nconst result = list.some((person, index, array) =&gt; {\n  console.log(person, index, array);\n  return person.age &gt; 25;\n});\nconsole.log(`result: ${result}`);<\/pre>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"js\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"true\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/ for..of\nvar myArray = [ 1, 2, 3 ];\nfor (var v of myArray) {\n\tconsole.log( v );\n}\n\/\/ 1\n\/\/ 2\n\/\/ 3<\/pre>\n\n\n<p>\u7269\u4ef6\u6c92\u6709\u5167\u5efa\u7684 @@iterator (\u8fed\u4ee3\u5668)\uff0c\u53ef\u4ee5\u70ba\u7269\u4ef6\u5b9a\u7fa9\u81ea\u5df1\u7684\u8fed\u4ee3\u5668\uff0c\u4e26\u642d\u914d ES6 \u7684 <code>for..of<\/code> \u505a\u4f7f\u7528\u3002<\/p>\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"js\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"true\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">var myObject = {\n\ta: 2,\n\tb: 3\n};\nObject.defineProperty( myObject, Symbol.iterator, {\n\tenumerable: false,\n\twritable: false,\n\tconfigurable: true,\n\tvalue: function() {\n\t\tvar o = this;\n\t\tvar idx = 0;\n\t\tvar ks = Object.keys( o );\n\t\treturn {\n\t\t\tnext: function() {\n\t\t\t\treturn {\n\t\t\t\t\tvalue: o[ks[idx++]],\n\t\t\t\t\tdone: (idx &gt; ks.length)\n\t\t\t\t};\n\t\t\t}\n\t\t};\n\t}\n} );\n\/\/ iterate `myObject` with `for..of`\nfor (var v of myObject) {\n\tconsole.log( v );\n}\n\/\/ 2\n\/\/ 3<\/pre>\n\n\n<h4 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"%E8%A4%87%E7%BF%92\"><\/span><strong>\u8907\u7fd2<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n<ul class=\"wp-block-list\"><li>JS \u4e2d\u7269\u4ef6\u5177\u6709\u5b57\u9762\u503c\u5f62\u5f0f\u548c\u5efa\u69cb\u5f62\u5f0f\uff0c\u591a\u6578\u60c5\u6cc1\u4e0b\u512a\u5148\u4f7f\u7528\u5b57\u9762\u503c\u5f62\u5f0f\uff0c\u4f46\u5efa\u69cb\u5f62\u5f0f\u80fd\u5920\u63d0\u4f9b\u66f4\u591a\u7684\u5275\u5efa\u9078\u9805\u3002<\/li><li>JS \u4e2d\u6709\u516d\u7a2e\u57fa\u672c\u578b\u5225\u3002<\/li><li>\u7269\u4ef6\u662f\u7531 key \/ value \u6240\u69cb\u6210\u7684\u7fa4\u96c6\uff0c\u5176\u4e2d\u7684\u503c\u53ef\u4f7f\u7528\u7279\u6027\u4f86\u5b58\u53d6\u3002<\/li><li>\u7279\u6027\u5177\u6709\u7279\u5fb5\uff0c\u53ef\u4ee5\u900f\u904e\u7279\u6027\u63cf\u8ff0\u5668\u4f86\u63a7\u5236\u3002\u4f7f\u7528\u5c0d\u61c9\u7684\u65b9\u6cd5\u4f86\u63a7\u5236\u7269\u4ef6\u7684\u53ef\u8b8a\u6027\u3002<\/li><li>\u53ef\u4ee5\u4f7f\u7528 for..of \u4f86\u8fed\u4ee3\u9663\u5217\u6216\u7269\u4ef6\u4e2d\u7684\u503c\uff0c\u5b83\u6703\u5c0b\u627e\u8fed\u4ee3\u5668\u7269\u4ef6\uff0c\u4e00\u6b21\u63d0\u53d6\u4e00\u500b\u503c\u51fa\u4f86\u3002<\/li><\/ul>\n","protected":false},"excerpt":{"rendered":"<p>\u8a9e\u6cd5 \u5ba3\u544a\u5f0f (declarative)\u3001\u5b57\u9762\u503c &hellip;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"pgc_sgb_lightbox_settings":"","footnotes":""},"categories":[13,12],"tags":[21],"class_list":["post-356","post","type-post","status-publish","format-standard","hentry","category-jsclosuresthis","category-12","tag-javascript"],"_links":{"self":[{"href":"https:\/\/wp.winter-weng.cc\/work\/index.php?rest_route=\/wp\/v2\/posts\/356","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wp.winter-weng.cc\/work\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wp.winter-weng.cc\/work\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wp.winter-weng.cc\/work\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/wp.winter-weng.cc\/work\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=356"}],"version-history":[{"count":0,"href":"https:\/\/wp.winter-weng.cc\/work\/index.php?rest_route=\/wp\/v2\/posts\/356\/revisions"}],"wp:attachment":[{"href":"https:\/\/wp.winter-weng.cc\/work\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=356"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wp.winter-weng.cc\/work\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=356"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wp.winter-weng.cc\/work\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=356"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}