{"id":7473,"date":"2018-04-10T22:37:37","date_gmt":"2018-04-10T14:37:37","guid":{"rendered":"http:\/\/www.zhangxinxu.com\/wordpress\/?p=7473"},"modified":"2018-04-11T19:53:58","modified_gmt":"2018-04-11T11:53:58","slug":"known-es6-symbol-function","status":"publish","type":"post","link":"https:\/\/www.zhangxinxu.com\/wordpress\/2018\/04\/known-es6-symbol-function\/","title":{"rendered":"\u7b80\u5355\u4e86\u89e3ES6\/ES2015 Symbol() \u65b9\u6cd5"},"content":{"rendered":"

by zhangxinxu<\/a> from http:\/\/www.zhangxinxu.com\/wordpress\/?p=7473<\/a>
\n\u672c\u6587\u53ef\u5168\u6587\u8f6c\u8f7d\uff0c\u4f46\u9700\u4fdd\u7559\u539f\u4f5c\u8005\u548c\u51fa\u5904\u3002<\/p>\n

\u4e00\u3001\u8def\u8fd8\u5f88\u8fdc\uff0c\u6162\u6162\u8d70\u4e00\u70b9\u4e00\u70b9<\/h3>\n

JS\u7684\u5b66\u4e60\u505c\u6ede\u4e86\u5f88\u4e45\uff0c\u5f53\u60f3\u8981\u91cd\u65b0\u62fe\u8d77\u7684\u65f6\u5019\uff0c\u53d1\u73b0\u5df2\u7ecf\u62c9\u4e86\u5f88\u591a\u4e1c\u897f\u4e86\u3002<\/p>\n

\u7136\u800c\uff0c\u81ea\u5df1\u5e76\u4e0d\u7740\u6025\u3002\u671d\u82b1\u56e0\u6545\u672a\u91c7\u64b7\uff0c\u5915\u62fe\u4f9d\u65e7\u70c2\u6f2b\u5929\u3002\u4ece\u5c0f\u5904\u5f00\u59cb\uff0c\u4e00\u70b9\u4e00\u70b9\u4e0a\u4e0b\u6c42\u7d22\uff0c\u6f2b\u6f2b\u957f\u8def\u5c31\u4f1a\u5168\u7136\u8d70\u5728\u811a\u4e0b\u3002<\/p>\n

\u4f8b\u5982\uff0c\u4eceES6\u4e00\u4e2a\u540d\u4e0d\u89c1\u7ecf\u4f20\u7684Symbol()<\/code>\u65b9\u6cd5\u8bf4\u8d77\u3002<\/p>\n

\/\/zxx: \u672c\u6587\u90e8\u5206\u5185\u5bb9\u53c2\u8003\u81eaMDN\u4e0a\u5173\u4e8eSymbol<\/a>\u7684\u6587\u6863\u3002<\/span><\/p>\n

\u4e8c\u3001\u5173\u4e8esymbol\u8fd9\u4e2a\u8bcd<\/h3>\n

Symbol\u8fd9\u4e2a\u8bcd\u5728IT\u8f6f\u4ef6\u9886\u57df\u5b9e\u9645\u4e0a\u662f\u4e2a\u5e38\u89c1\u89d2\u8272\uff0c\u5728\u4f20\u7edf\u524d\u7aef\u6280\u672f\u9886\u57df\uff0c\u8fd9\u4e2a\u8bcd\u51fa\u73b0\u9891\u7387\u6709\u9650\uff0c\u4f46\u662f\uff0c\u968f\u7740\u73b0\u4ee3web\u6280\u672f\u7684\u53d1\u5c55\uff0cSymbol\u8fd9\u4e2a\u8bcd\u5f00\u59cb\u5728\u4e0d\u540c\u524d\u7aef\u8bed\u8a00\u4e2d\u51fa\u73b0\u3002<\/p>\n

symbol\u7684\u4e2d\u6587\u610f\u601d\u662f\uff1a\u7b26\u53f7\uff1b\u8c61\u5f81\uff1b\u6807\u5fd7\uff1b\u8bb0\u53f7\u7b49\u3002<\/p>\n

\u6211\u6700\u65e9\u77e5\u9053\u662f\u5728Adobe Illustrator\u8f6f\u4ef6\u4e2d\uff0c\u4f5c\u4e3a\u4e00\u4e2a\u77e2\u91cf\u7b26\u53f7\u5b58\u5728\u3002\u5728SVG\u4e2d\uff0c\u5c31\u6709\u4e13\u95e8\u7684<symbol><\/code>\u6807\u7b7e\uff0c\u7528\u6765\u6307\u4ee3SVG\u5c0f\u56fe\u6807\u3002<\/p>\n

\u5728\u8fd9\u91cc\uff0cSymbol\u53c8\u6709\u4e86\u53e6\u5916\u7684\u89d2\u8272\uff0c\u4f5c\u4e3a\u4e00\u4e2aJavaScript\u7684\u539f\u751f\u6570\u636e\u7c7b\u578b\uff08primitive data type\uff09\u5b58\u5728\u3002<\/p>\n

\u8bf4\u5230JavaScript\u539f\u751f\u6570\u636e\u7c7b\u578b\uff0c\u6211\u4eec\u901a\u5e38\u60f3\u5230\u7684\u6709\u8fd96\u79cd\uff1aundefined<\/code>\u3001null<\/code>\u3001boolean<\/code>\u3001string<\/code>\u3001number<\/code>\u3001object<\/code>\u3002\u800csymbol<\/code>\u662fES6\u65b0\u589e\u7684\u4e00\u4e2a\u539f\u751f\u6570\u636e\u7c7b\u578b\u3002<\/p>\n

\u800cSymbol\u672c\u8eab\u53c8\u662f\u4e00\u4e2a\u65b9\u6cd5\u3002<\/p>\n

\u4f8b\u5982\u4e0b\u9762JS\uff1a<\/p>\n

typeof Symbol();<\/pre>\n
\u53ef\u4ee5\u770b\u5230Symbol()<\/code>\u4f5c\u4e3a\u4e00\u4e2a\u65b9\u6cd5\u6267\u884c\u4e86\uff0c\u540c\u65f6typeof<\/code>\u5176\u7c7b\u578b\uff0c\u4e5f\u662f'symbol'<\/code>\uff0c\u5982\u4e0b\u622a\u56fe\uff1a<\/p>\n
\"symbol\u7c7b\u578b\u663e\u793a\"<\/p>\n
\u4f46Symbol\u4e0d\u80fd\u4f5c\u4e3a\u6784\u9020\u51fd\u6570\u4f7f\u7528<\/strong>\uff0c\u4e5f\u5c31\u662f\u4e0b\u9762\u8fd9\u6837\u662f\u4f1a\u55dd\u5c41\u7684\uff01<\/p>\n
new Symbol();<\/pre>\n
\"\u4f5c\u4e3a\u6784\u9020\u51fd\u6570\u5931\u8d25\"<\/p>\n
\u4e09\u3001Symbol\u7684\u4f5c\u7528\u662f\u4ec0\u4e48\uff1f<\/h3>\n
Symbol\u7684\u4f5c\u7528\u975e\u5e38\u7684\u4e13\u4e00\uff0c\u6362\u53e5\u8bdd\u8bf4\u5176\u8bbe\u8ba1\u51fa\u6765\u5c31\u53ea\u6709\u4e00\u4e2a\u76ee\u7684\u2014\u2014\u4f5c\u4e3a\u5bf9\u8c61\u5c5e\u6027\u7684\u552f\u4e00\u6807\u8bc6\u7b26<\/strong>\uff0c\u9632\u6b62\u5bf9\u8c61\u5c5e\u6027\u51b2\u7a81\u53d1\u751f\u3002<\/p>\n
\u4e3e\u4e2a\u4f8b\u5b50\uff0c\u4f60\u770b\u4e0a\u4e86\u516c\u53f8\u524d\u6765\u7684\u524d\u53f0\u59b9\u7eb8\uff0c\u60f3\u4e86\u89e3\u5173\u4e8e\u5979\u7684\u66f4\u591a\u4fe1\u606f\uff0c\u4e8e\u662f\u5c31\u8be2\u95eeHr\u540c\u4e8b\uff0c\u626b\u5730\u963f\u59e8\uff0c\u4e8e\u662f\u5f97\u5230\u7c7b\u4f3c\u8fd9\u6837\u4fe1\u606f\uff1a<\/p>\n
let info1 = {\n    name: '\u5a77\u5a77',\n    age: 24,\n    job: '\u516c\u53f8\u524d\u53f0',\n    description: '\u5e73\u65f6\u559c\u6b22\u505a\u505a\u745c\u4f3d\uff0c\u4eba\u5bb6\u6709\u7537\u670b\u53cb\uff0c\u4f60\u522b\u6307\u671b\u4e86'\n}\nlet info2 = {\n    description: '\u8fd9\u5c0f\u59d1\u5a18\u633a\u597d\u7684\uff0c\u633a\u70ed\u60c5\u7684\uff0c\u563f\u563f\u563f\u2026\u2026'\n}<\/pre>\n
\u663e\u7136\uff0c\u4f60\u9700\u8981\u5bf9\u8fd9\u4e24\u4e2a\u6570\u636e\u8fdb\u884c\u6c47\u603b\uff0c\u7ed3\u679c\uff0c\u5c31\u4f1a\u53d1\u73b0\uff0c\u63cf\u8ff0\u90fd\u7528\u4e86\u540c\u4e00\u4e2a\u5bf9\u8c61\u5c5e\u6027description<\/code>\uff0c\u4e8e\u662f\u6574\u5408\u7684\u65f6\u5019\uff0c\u5c31\u5bb9\u5668\u51b2\u7a81\uff0c\u8986\u76d6\uff0c\u5bfc\u81f4\u201c\u4eba\u5bb6\u6709\u7537\u670b\u53cb\u201d\u8fd9\u4e48\u91cd\u8981\u7684\u4fe1\u606f\u90fd\u6ca1\u6ce8\u610f\u5230\u3002<\/p>\n
\u4f46\u662f\uff0c\u5982\u679c\u8981\u662fSymbol\uff0c\u5219\u5b8c\u5168\u5c31\u4e0d\u8981\u62c5\u5fc3\u8fd9\u4e2a\u95ee\u9898\u4e86\uff1a<\/p>\n
let info1 = {\n    name: '\u5a77\u5a77',\n    age: 24,\n    job: '\u516c\u53f8\u524d\u53f0',\n    [Symbol('description')]: '\u5e73\u65f6\u559c\u6b22\u505a\u505a\u745c\u4f3d\uff0c\u4eba\u5bb6\u6709\u7537\u670b\u53cb\uff0c\u4f60\u522b\u6307\u671b\u4e86'\n}\nlet info2 = {\n    [Symbol('description')]: '\u8fd9\u5c0f\u59d1\u5a18\u633a\u597d\u7684\uff0c\u633a\u70ed\u60c5\u7684\uff0c\u563f\u563f\u563f\u2026\u2026'\n}<\/pre>\n
\u6b64\u65f6\uff0c\u6211\u4eec\u5bf9info1, info2\u5bf9\u8c61\u8fdb\u884c\u590d\u5236\uff0c\u5982\u4e0b\uff1a<\/p>\n
let target = {};\nObject.assign(target, info1, info2);<\/pre>\n
\u6b64\u65f6target<\/code>\u5bf9\u8c61\u5982\u4e0b\u622a\u56fe\u6240\u793a\uff1a<\/p>\n
\"target\u5bf9\u8c61\u8f93\u51fa\u622a\u56fe\"<\/p>\n
\u59b9\u7eb8\u6240\u6709\u7684\u63cf\u8ff0\u4fe1\u606f\u90fd\u88ab\u5b8c\u5b8c\u6574\u6574\u5730\u4fdd\u7559\u4e86\u4e0b\u6765\u4e86\u3002<\/p>\n
\u56e0\u4e3aSymbol()<\/code>\u8fd4\u56de\u503c\u662f\u552f\u4e00\u7684\uff0c\u4e5f\u5c31\u662f\uff1a<\/p>\n
Symbol('description') === Symbol('description');    \/\/ \u8fd4\u56de\u503c\u662ffalse<\/span><\/pre>\n
\u56db\u3001Symbol()\u7684\u8bed\u6cd5<\/h3>\n
\u8bed\u6cd5\u5982\u4e0b\uff1a<\/p>\n
Symbol([description])<\/pre>\n
\u5176\u4e2ddescription<\/code>\u4e3a\u53ef\u9009\u53c2\u6570\uff0c\u5b57\u7b26\u4e32\uff0c\u6ca1\u4ec0\u4e48\u7279\u522b\u7684\u4f5c\u7528\uff0c\u5c31\u662fdebug\u8c03\u8bd5\u7684\u65f6\u5019\u53ef\u4ee5\u7528\u6765\u4f5c\u4e3a\u6807\u8bb0\u3002<\/p>\n
\u5982\u4f55\u83b7\u53d6Symbol()\u5bf9\u5e94\u5c5e\u6027\u503c\uff1f<\/h4>\n
\u62ff\u4e0a\u9762target<\/code>\u4e3e\u4f8b\uff0c\u5982\u4f55\u83b7\u5f97\u5bf9\u59b9\u7eb8\u7684description<\/code>\u63cf\u8ff0\u4fe1\u606f\u5462\uff1f<\/p>\n
\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528Object.getOwnPropertySymbols(obj)<\/code>\u8fd9\u4e2a\u65b9\u6cd5\u8fdb\u884c\u83b7\u53d6\uff0c\u53ef\u4ee5\u8fd4\u56deobj<\/code>\u5bf9\u8c61\u4e2d\u7684Symbol\u4fe1\u606f\uff0c\u4f8b\u5982\uff1a<\/p>\n
Object.getOwnPropertySymbols(target);<\/pre>\n
\u59b9\u7eb8\u7684\u63cf\u8ff0\u4fe1\u606f\u5c31\u51fa\u73b0\u4e86\uff0c\u5982\u4e0b\u622a\u56fe\uff1a<\/p>\n
\"\u59b9\u7eb8\u7684\u63cf\u8ff0\u4fe1\u606f\"<\/p>\n
Symbol\u5728\u548c\u5bf9\u8c61\u4f7f\u7528\u7684\u65f6\u5019\uff0c\u5f80\u5f80\u79bb\u4e0d\u5f00JS\u4e2d\u7684\u6570\u7ec4\u62ec\u53f7[]<\/code>\uff0c\u4f8b\u5982\uff1a<\/p>\n
var smy = Symbol();\nvar info = {\n  smy: 'x',\n  [smy]: 'y'\n};\n<\/pre>\n
\u6b64\u65f6\uff1a<\/p>\n
console.log(info.smy);       \/\/ \u8f93\u51fa'x'<\/span>\nconsole.log(info['smy']);    \/\/ \u8f93\u51fa'x'<\/span>\nconsole.log(info[smy]);      \/\/ \u8f93\u51fa'y'<\/span><\/pre>\n
\u4e94\u3001Symbol\u5176\u4ed6\u4e00\u4e9b\u77e5\u8bc6<\/h3>\n
1. Symbol\u4e0e\u8fd0\u7b97\u3001\u7c7b\u578b\u8f6c\u6362\u7b49<\/h4>\n
symbol<\/code>\u503c\u867d\u7136\u4e0d\u662f\u5bf9\u8c61\uff0c\u4f46\u662f\u6839\u636e\u81ea\u5df1\u6d4b\u8bd5\uff0c\u5728Chrome\u548cFirefox\u4e0b\u90fd\u662f\u53ef\u4ee5\u6dfb\u52a0\u5c5e\u6027\u7684\uff0c\u4f8b\u5982\uff1a<\/p>\n
var smy = Symbol();\nsmy.description = '\u63cf\u8ff0';<\/pre>\n
\"\u6dfb\u52a0\u5c5e\u6027\"<\/p>\n
\u66f4\u65b0\u4e8e\u7fcc\u65e5<\/strong>
\n\u611f\u8c22yyhaxx\u7684\u53cd\u9988\uff0c\u5728macos chrome 65.0.3325.181\u548cnode v8.9.4\u4e2d\u6d4b\u8bd5\u7ed9symbol\u52a0\u5c5e\u6027\u7ed3\u679c\u662fundefined<\/code>\uff0c\u4e0e\u4e0a\u9762window PC\u6d4b\u8bd5\u7ed3\u679c\u6709\u4e9b\u7ec6\u8282\u5dee\u5f02\u3002<\/p>\n
\u4f46\u662f\u5728\u7c7b\u578b\u8f6c\u6362\u65f6\u5019symbol<\/code>\u503c\u4f1a\u9047\u5230\u4e0d\u5c11\u5c40\u9650\uff1a<\/p>\n