{"id":31388,"date":"2024-11-25T12:23:03","date_gmt":"2024-11-25T04:23:03","guid":{"rendered":"https:\/\/fwq.ai\/blog\/31388\/"},"modified":"2024-11-25T12:23:03","modified_gmt":"2024-11-25T04:23:03","slug":"javascript%e7%9a%84%e9%9a%90%e5%bc%8f%e8%b0%83%e7%94%a8%e8%af%a6%e8%a7%a3","status":"publish","type":"post","link":"https:\/\/fwq.ai\/blog\/31388\/","title":{"rendered":"javascript\u7684\u9690\u5f0f\u8c03\u7528\u8be6\u89e3"},"content":{"rendered":"

\u8fd9\u6b21\u7ed9\u5927\u5bb6\u5e26\u6765javascript\u7684\u9690\u5f0f\u8c03\u7528\u8be6\u89e3\uff0c\u9690\u5f0f\u8c03\u7528\u7684\u6709\u54ea\u4e9b\uff0c\u4e0b\u9762\u5c31\u662f\u5b9e\u6218\u6848\u4f8b\uff0c\u4e00\u8d77\u6765\u770b\u4e00\u4e0b\u3002<\/p>\n

\u524d\u8a00<\/p>\n

\u4e0d\u77e5\u9053\u7528\u9690\u5f0f\u8c03\u7528\u6765\u5f62\u5bb9\u662f\u5426\u786e\u5207,\u5176\u884c\u4e3a\u603b\u662f\u9690\u85cf\u5728\u80cc\u540e\uff0c\u65f6\u4e0d\u65f6\u51fa\u6765\u9732\u8138\u4e00\u4e0b\uff0c\u4f5c\u7528\u8c8c\u4f3c\u4e0d\u5927\uff0c\u4f46\u662f\u4e86\u89e3\u4e00\u4e0b\u8fd8\u662f\u6709\u7528\u5904\u7684\uff0c\u4fdd\u4e0d\u51c6\u5728\u4f60\u7684\u4f7f\u7528\u4e0b\u5927\u6709\u4f5c\u4e3a\u3002<\/p>\n

\u6240\u8c13\u7684\u9690\u5f0f\u8c03\u7528\u7b80\u5355\u6765\u8bf4\u5c31\u662f\u81ea\u52a8\u8c03\u7528\u4e00\u4e9b\u65b9\u6cd5\uff0c\u800c\u8fd9\u4e9b\u65b9\u6cd5\u50cf\u94a9\u5b50\u4e00\u6837\u53ef\u4ee5\u5728\u5916\u90e8\u4fee\u6539\uff0c\u4ece\u800c\u6539\u53d8\u65e2\u5b9a\u884c\u4e3a\u3002
\u4e0b\u9762\u6211\u4f1a\u5217\u4e3e\u4e00\u4e9b\u6700\u8fd1\u770b\u5230\u7684\u9690\u5f0f\u8c03\u7528\uff0c\u4f8b\u5b50\u90fd\u662f\u70b9\u5230\u5373\u6b62\uff0c\u6b22\u8fce\u8865\u5145<\/p>\n

\u6570\u636e toSting \u548c valueOf<\/strong><\/p>\n

var obj = {\r\n   a: 1,\r\n   toString: function () {\r\n    console.log('toString')\r\n    return '2'\r\n   },\r\n   valueOf: function () {\r\n    console.log('valueOf')\r\n    return 3\r\n   }\r\n  }\r\n  console.log(obj == '2'); \/\/\u4f9d\u6b21\u8f93\u51fa 'valueOf' false\r\n  console.log(String(obj));\/\/\u4f9d\u6b21\u8f93\u51fa 'toString' '2'<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
var obj = {\r\n   a: 1,\r\n   toString: function () {\r\n    console.log('toString')\r\n    return '2'\r\n   },\r\n   valueOf: function () {\r\n    console.log('valueOf')\r\n    return {} \/\/\u4fee\u6539\u4e3a\u5bf9\u8c61\r\n   }\r\n  }\r\n  console.log(obj == '2'); \/\/\u4f9d\u6b21\u8f93\u51fa 'valueOf' 'toString' true\r\n  console.log(Number(obj));\/\/\u4f9d\u6b21\u8f93\u51fa 'valueOf' 'toString' 2<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u5728\u76f8\u7b49\u8fd0\u7b97\u7b26\u7684\u64cd\u4f5c\u4e2d\uff0c\u5bf9\u8c61\u4f1a\u5148\u8c03\u7528 valueOf \u5982\u679c\u8fd4\u56de\u7684\u503c\u662f\u4e00\u4e2a\u5bf9\u8c61, \u5c31\u4f1a\u8c03\u7528 toSting\uff0c null\u9664\u5916\uff0c\u7136\u540e\u7528\u8fd4\u56de\u7684\u503c\u8fdb\u884c\u6bd4\u8f83\uff0c\u7b2c\u4e00\u4e2a\u4f8b\u5b50 \u76f8\u5f53\u4e8e 3 == ‘2’ \u8f93\u51fa false\uff0c \u7b2c\u4e8c\u4e2a\u4f8b\u5b50\u7531\u4e8e\u6267\u884cvalueOf \u8fd4\u56de\u7684\u662f\u4e00\u4e2a\u5bf9\u8c61\uff0c \u7136\u540e\u6267\u884c toString\uff0c \u6700\u540e\u76f8\u5f53\u4e8e ‘2’ == ‘2’ \u8f93\u51fatrue\u5728 Number \u548c String \u65b9\u6cd5\u4e2d Number\u4f1a\u5148\u8c03\u7528 valueOf, \u540e\u8c03\u7528 toString\uff0c String\u65b9\u6cd5\u4e2d\u662f\u76f8\u53cd\u7684\u3002<\/p>\n
\u7684\u8f6c\u6362\u9664\u4e86\u4e0a\u9762\u7684\u4e24\u4e2a\u4f8b\u5b50\u5916\uff0c\u8fd8\u5b58\u5728\u5728\u5404\u79cd\u5176\u4ed6\u64cd\u4f5c\u4e2d\uff0c\u5982\u6570\u503c\u8fd0\u7b97\uff0c\u5f53\u6d89\u53ca\u5230\u5f15\u7528\u7c7b\u578b\u65f6\uff0c\u90fd\u4f1a\u8c03\u7528valueOf \u6216 toString \u65b9\u6cd5\uff0c\u53ea\u8981\u662f\u5bf9\u8c61\u90fd\u4f1a\u7ee7\u627f\u8fd9\u4e24\u4e2a\u65b9\u6cd5,\u6211\u4eec\u53ef\u4ee5\u91cd\u65b0\u8986\u76d6\u8fd9\u4e24\u4e2a\u65b9\u6cd5\uff0c\u4ece\u800c\u5f71\u54cd\u6570\u636e\u7c7b\u578b\u8f6c\u6362\u7684\u884c\u4e3a<\/p>\n
DOM2\u4e8b\u4ef6\u4e2d\u7684 handleEvent <\/strong><\/p>\n
var eventObj = {\r\n   a: 1,\r\n   handleEvent: function (e) {\r\n    console.log(this, e);\/\/\u8fd4\u56de eventObj \u548c \u4e8b\u4ef6\u5bf9\u8c61\r\n    alert(this.a)\r\n   }\r\n  }\r\n  document.addEventListener('click', eventObj)<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u4f60\u6ca1\u6709\u770b\u9519\uff0caddEventListener \u7b2c\u4e8c\u4e2a\u53c2\u6570\u9664\u4e86\u51fd\u6570\u5916\u8fd8\u53ef\u4ee5\u662f\u4e00\u4e2a\u5bf9\u8c61, \u4e8b\u4ef6\u89e6\u53d1\u540e\u4f1a\u6267\u884c\u5bf9\u8c61\u7684handleEvent\u65b9\u6cd5,\u65b9\u6cd5\u6267\u884c\u65f6\u7684this\u6307\u5411eventObj, \u4f60\u53ef\u4ee5\u628a\u60f3\u4f20\u5165\u7684\u5728eventObj\u5bf9\u8c61\u4e0a<\/p>\n
JSON\u5bf9\u8c61 toJSON <\/strong><\/p>\n
var Obj = {\r\n   a: 10,\r\n   toJSON: function () {\r\n    return {\r\n     a: 1,\r\n     b: function () {\r\n     },\r\n     c: NaN,\r\n     d: -Infinity,\r\n     e: Infinity,\r\n     f: \/d\/,\r\n     g: new Error(),\r\n     h: new Date(),\r\n     i: undefined,\r\n     \r\n    }\r\n   }\r\n  }\r\n  console.log(JSON.stringify(Obj));\r\n  \/\/{\"a\":1,\"c\":null,\"d\":null,\"e\":null,\"f\":{},\"g\":{},\"h\":\"2018-02-09T19:29:13.828Z\"}<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u5982\u679cJSON\u7684stringify\u65b9\u6cd5\u4f20\u5165\u7684\u5bf9\u8c61\u6709toJSON\u65b9\u6cd5,\u90a3\u4e48\u8be5\u65b9\u6cd5\u6267\u884c\u7684\u5bf9\u8c61\u4f1a\u8f6c\u4e3atoJSON\u6267\u884c\u540e\u8fd4\u56de\u7684\u5bf9\u8c61,\u6709\u4e00\u70b9\u8981\u6ce8\u610f\u7684\u662f\uff0c\u5982\u4e0b\u9762\u4ee3\u7801<\/p>\n
var Obj1 = {\r\n   a: 10,\r\n   toJSON: function () {\r\n    console.log(this === Obj1);\/\/true\r\n    return this\r\n   }\r\n  }\r\n  console.log(JSON.stringify(Obj1));\/\/{\"a\":10}<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
 var Obj2 = {\r\n   a: 10,\r\n   toJSON: function () {\r\n    console.log(this === Obj2);\/\/true\r\n    return {\r\n     a: this\r\n    }\r\n   }\r\n  }\r\n  console.log(JSON.stringify(Obj2));\/\/\u62a5\u9519 Maximum call stack size exceeded<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u5982\u679c\u6309\u4e0a\u9762\u7684\u8bf4\u6cd5\u5f88\u660e\u663e\u62a5\u9519\u662f\u6211\u4eec\u6240\u9884\u671f\u7684\uff0c\u4f46\u662f\u5f53\u76f4\u63a5 return this \u6839\u672c\u6ca1\u6709\u62a5\u9519\uff0c\u4e0d\u59a8\u53ef\u4ee5\u5927\u80c6\u731c\u6d4b\u4e00\u4e0b\u5176\u5185\u90e8\u5bf9toJSON\u8fd4\u56de\u7684\u5bf9\u8c61\u548c\u539f\u5bf9\u50cf\u8fdb\u884c\u6bd4\u8f83,\u5982\u679c\u76f8\u7b49\u5c31\u76f4\u63a5\u4f7f\u7528\u539f\u5bf9\u8c61<\/p>\n
promise\u5bf9\u8c61\u7684 then<\/strong><\/p>\n
var obj = {\r\n   then: function (resolve, reject) {\r\n    setTimeout(function () {\r\n     resolve(1000);\r\n    }, 1000)\r\n   }\r\n  }\r\n  Promise.resolve(obj).then(function (data) {\r\n   console.log(data);\/\/ \u5ef6\u8fdf1\u79d2\u5de6\u53f3\u8f93\u51fa 1000\r\n  })<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u5f53Promise.resolve\u65b9\u6cd5\u4f20\u5165\u5bf9\u8c61\u65f6,\u5982\u679c\u5b58\u5728 then \u65b9\u6cd5\u4f1a\u7acb\u5373\u6267\u884cthen\u65b9\u6cd5,\u76f8\u5f53\u4e8e\u628a\u65b9\u6cd5\u653e\u5165new Promise\u4e2d,\u9664\u4e86Promise.resolve\u6709\u8fd9\u4e2a\u884c\u4e3a\u5916,Promise.all\u4e5f\u6709\u8fd9\u4e2a\u884c\u4e3a<\/p>\n
 var timePromise = function (time) {\r\n    return new Promise(function (resolve) {\r\n     setTimeout(function () {\r\n      resolve(time);\r\n     }, time)\r\n    })\r\n   }\r\n   var timePromise1 = timePromise(1000);\r\n   var timePromise2 = timePromise(2000);\r\n   var timePromise3 = timePromise(3000);\r\n   Array.prototype.then = function (resolve) {\r\n     setTimeout(function () {\r\n      resolve(4000);\r\n     }, 4000)\r\n    }\r\n   Promise.all([timePromise1, timePromise2, timePromise3]).then(function (time) {\r\n    console.log(time);\/\/ \u7b49\u5f854\u79d2\u5de6\u53f3\u8f93\u51fa 4000\r\n   })<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u5bf9\u8c61\u5c5e\u6027\u5b58\u53d6\u5668 get \u548c set<\/strong><\/p>\n
var obj = {\r\n    _age: 100,\r\n    get age() {\r\n     return this._age < 18 ? this._age : 18;\r\n    },\r\n    set age(value) {\r\n     this._age = value;\r\n     console.log(`\u5e74\u9f84\u8bbe\u7f6e\u4e3a${value}\u5c81`);\r\n    }\r\n   }\r\n   obj.age = 1000; \/\/\u5e74\u9f84\u8bbe\u7f6e\u4e3a1000\u5c81\r\n   obj.age = 200; \/\/\u5e74\u9f84\u8bbe\u7f6e\u4e3a200\u5c81\r\n   console.log(obj.age);\/\/ 18\r\n   obj.age = 2; \/\/\/\/\u5e74\u9f84\u8bbe\u7f6e\u4e3a2\u5c81\r\n   console.log(obj.age); \/\/ 2<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u53ef\u4ee5\u770b\u5230\u4e0d\u7ba1\u628a\u5e74\u9f84\u8bbe\u7f6e\u4e3a\u591a\u5c11,\u6211\u7684\u5e74\u9f84\u90fd\u662f18\u5c81\u6216\u4ee5\u4e0b\u7684,\u5f53\u6267\u884c\u5c5e\u6027\u5b58\u53d6\u65f6\u5b9e\u9645\u4e0a\u662f\u8c03\u7528\u5bf9\u8c61\u5c5e\u6027\u76f8\u5e94\u7684 get set\u51fd\u6570\uff0c\u9664\u4e86\u4ee5\u4e0a\u5199\u6cd5\u8fd8\u6709\u4e0b\u9762\u7684\u5199\u6cd5<\/p>\n
 var input = document.createElement('input');\r\n  var span = document.createElement('span');\r\n  document.body.appendChild(input);\r\n  document.body.appendChild(span);\r\n  var obj = {\r\n   _age:''\r\n  }\r\n  var obj = Object.defineProperty(obj, 'age', {\r\n   get: function () {\r\n    return this._age;\r\n   },\r\n   set: function (value) {\r\n    this._age = value;\r\n    input.value = value;\r\n    span.innerHTML = value;\r\n   }\r\n  });\r\n  input.onkeyup = function (e) {\r\n   if (e.keyCode === 37 || e.keyCode === 39) {\r\n    return;\r\n   }\r\n   obj.age = this.value\r\n  }<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u73b0\u5728input\u7684value\u503c\u548cobj.age\u7684\u5c5e\u6027\u503cspan\u7684innerHTML\u503c\u90fd\u7ed1\u5b9a\u5728\u4e00\u8d77\u4e86<\/p>\n
\u904d\u5386\u5668\u63a5\u53e3 Symbol.iterator<\/strong><\/p>\n
 var arr = [ 1, 2 , 3];\r\n  arr[Symbol.iterator] = function () {\r\n   const self = this;\r\n   let index = 0;\r\n   return {\r\n    next () {\r\n     if(index < self.length) {\r\n      return {\r\n       value: self[index] ** self[index++],\r\n       done: false\r\n      }\r\n     } else {\r\n      return {\r\n       value: undefined,\r\n       done: true\r\n      }\r\n     }\r\n    }\r\n   }\r\n  }\r\n  console.log([...arr, 4]);\/\/\u8fd4\u56de [1, 4, 27, 4]\r\n  for(let value of arr) {\r\n   console.log(value); \/\/\u4f9d\u6b21\u8fd4\u56de 1 4 27\r\n  }<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u76f8\u4fe1\u770b\u4e86\u672c\u6587\u6848\u4f8b\u4f60\u5df2\u7ecf\u638c\u63e1\u4e86\u65b9\u6cd5\uff0c\u66f4\u591a\u7cbe\u5f69\u8bf7\u5173\u6ce8\u7c73\u4e91\u5176\u5b83\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n
\u63a8\u8350\u9605\u8bfb\uff1a<\/p>\n
<\/p>\n
<\/p>\n
<\/p>\n
\u4ee5\u4e0a\u5c31\u662fjavascript\u7684\u9690\u5f0f\u8c03\u7528\u8be6\u89e3\u7684\u8be6\u7ec6\u5185\u5bb9\uff0c\u66f4\u591a\u8bf7\u5173\u6ce8\u7c73\u4e91\u5176\u5b83\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"
\u8fd9\u6b21\u7ed9\u5927\u5bb6\u5e26\u6765javascript\u7684\u9690\u5f0f\u8c03\u7528\u8be6\u89e3\uff0c\u9690\u5f0f\u8c03\u7528\u7684\u6709\u54ea\u4e9b\uff0c\u4e0b\u9762\u5c31\u662f\u5b9e\u6218\u6848\u4f8b\uff0c\u4e00\u8d77\u6765\u770b\u4e00\u4e0b\u3002 \u524d\u8a00 \u4e0d\u77e5\u9053\u7528\u9690\u5f0f\u8c03\u7528\u6765\u5f62\u5bb9\u662f\u5426\u786e\u5207,\u5176\u884c\u4e3a\u603b\u662f\u9690\u85cf\u5728\u80cc\u540e\uff0c\u65f6\u4e0d\u65f6\u51fa\u6765\u9732\u8138\u4e00\u4e0b\uff0c\u4f5c\u7528\u8c8c\u4f3c\u4e0d\u5927\uff0c\u4f46\u662f\u4e86\u89e3\u4e00\u4e0b\u8fd8\u662f\u6709\u7528\u5904\u7684\uff0c\u4fdd\u4e0d\u51c6\u5728\u4f60\u7684\u4f7f\u7528\u4e0b\u5927\u6709\u4f5c\u4e3a\u3002 \u6240\u8c13\u7684\u9690\u5f0f\u8c03\u7528\u7b80\u5355\u6765\u8bf4\u5c31\u662f\u81ea\u52a8\u8c03\u7528\u4e00\u4e9b\u65b9\u6cd5\uff0c\u800c\u8fd9\u4e9b\u65b9\u6cd5\u50cf\u94a9\u5b50\u4e00\u6837\u53ef\u4ee5\u5728\u5916\u90e8\u4fee\u6539\uff0c\u4ece\u800c\u6539\u53d8\u65e2\u5b9a\u884c\u4e3a\u3002\u4e0b\u9762\u6211\u4f1a\u5217\u4e3e\u4e00\u4e9b\u6700\u8fd1\u770b\u5230\u7684\u9690\u5f0f\u8c03\u7528\uff0c\u4f8b\u5b50\u90fd\u662f\u70b9\u5230\u5373\u6b62\uff0c\u6b22\u8fce\u8865\u5145 \u6570\u636e toSting \u548c valueOf var obj = { a: 1, toString: function () { console.log(‘toString’) return ‘2’ }, valueOf: function () { console.log(‘valueOf’) return 3 } } console.log(obj == ‘2’); \/\/\u4f9d\u6b21\u8f93\u51fa ‘valueOf’ false console.log(String(obj));\/\/\u4f9d\u6b21\u8f93\u51fa ‘toString’ ‘2’ \u767b\u5f55\u540e\u590d\u5236 var obj = { a: 1, toString: function () { console.log(‘toString’) return ‘2’ }, […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[19],"tags":[],"class_list":["post-31388","post","type-post","status-publish","format-standard","hentry","category-19"],"_links":{"self":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/31388","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/comments?post=31388"}],"version-history":[{"count":0,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/31388\/revisions"}],"wp:attachment":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/media?parent=31388"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/categories?post=31388"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/tags?post=31388"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}