{"id":315118,"date":"2024-05-20T23:52:06","date_gmt":"2024-05-20T15:52:06","guid":{"rendered":"https:\/\/docs.pingcode.com\/ask\/ask-ask\/315118.html"},"modified":"2024-05-20T23:52:28","modified_gmt":"2024-05-20T15:52:28","slug":"javascript-%e4%b8%ad%e7%9a%84-this-%e6%9c%89%e5%93%aa%e4%ba%9b%e7%94%a8%e5%a4%84-2","status":"publish","type":"post","link":"https:\/\/docs.pingcode.com\/ask\/315118.html","title":{"rendered":"JavaScript \u4e2d\u7684 this \u6709\u54ea\u4e9b\u7528\u5904"},"content":{"rendered":"

\"JavaScript<\/p>\n

JavaScript \u4e2d\u7684 this \u5173\u952e\u5b57\u4e3b\u8981\u7528\u4e8e\u5728\u51fd\u6570\u6216\u65b9\u6cd5\u4e2d\u5f15\u7528\u5f53\u524d\u6267\u884c\u4e0a\u4e0b\u6587\u7684\u5bf9\u8c61\u3001\u63d0\u4f9b\u4ee3\u7801\u7684\u6a21\u5757\u5316\u4e0e\u91cd\u7528\u6027\u3001\u5141\u8bb8\u5bf9\u8c61\u6784\u9020\u65f6\u7684\u52a8\u6001\u4f5c\u7528\u57df\u7ed1\u5b9a\u3001\u4ee5\u53ca\u5728\u51fd\u6570\u5f0f\u7f16\u7a0b\u4e2d\u7ed1\u5b9a\u4e0a\u4e0b\u6587\u3002\u5b83\u4f7f\u5f97\u65b9\u6cd5\u53ef\u4ee5\u5728\u4e0d\u540c\u5bf9\u8c61\u95f4\u5171\u4eab\uff0c\u51cf\u5c11\u4ee3\u7801\u5197\u4f59\uff0c\u5e76\u4e0e\u9762\u5411\u5bf9\u8c61\u7f16\u7a0b\u7684\u6982\u5ff5\u76f8\u7ed3\u5408<\/strong>\u3002\u4f8b\u5982\uff0c\u5728\u4e00\u4e2a\u5bf9\u8c61\u7684\u65b9\u6cd5\u91cc\uff0cthis \u6307\u4ee3\u8c03\u7528\u6b64\u65b9\u6cd5\u7684\u90a3\u4e2a\u5bf9\u8c61\uff0c\u8fd9\u6837\u5373\u4f7f\u591a\u4e2a\u5bf9\u8c61\u5171\u7528\u540c\u4e00\u4e2a\u51fd\u6570\u5b9a\u4e49\uff0cthis \u7684\u503c\u4e5f\u4f1a\u6839\u636e\u6240\u5c5e\u7684\u5bf9\u8c61\u800c\u4e0d\u540c\uff0c\u4ece\u800c\u6267\u884c\u76f8\u5bf9\u5e94\u5bf9\u8c61\u7684\u5c5e\u6027\u6216\u65b9\u6cd5\u3002\u5728\u4e8b\u4ef6\u5904\u7406\u4e2d\uff0cthis \u5e38\u7528\u4e8e\u5f15\u7528\u89e6\u53d1\u4e8b\u4ef6\u7684\u5143\u7d20\u3002\u6b64\u5916\uff0cthis \u8fd8\u53ef\u4ee5\u5728\u65b0\u521b\u5efa\u7684\u5b9e\u4f8b\u5bf9\u8c61\u4e2d\u901a\u8fc7\u6784\u9020\u51fd\u6570\u5f15\u7528\u8be5\u5b9e\u4f8b\u5bf9\u8c61\u672c\u8eab\u3002<\/p>\n<\/p>\n

\u4e00\u3001\u5bf9\u8c61\u65b9\u6cd5\u4e2d\u7684 this<\/h3>\n<\/p>\n

JavaScript \u4e2d\u4f7f\u7528 this \u6700\u5e38\u89c1\u7684\u573a\u666f\u662f\u5728\u5bf9\u8c61\u7684\u65b9\u6cd5\u4e2d\u3002\u5728\u65b9\u6cd5\u5185\u90e8\uff0cthis \u6307\u5411\u8c03\u7528\u8be5\u65b9\u6cd5\u7684\u5bf9\u8c61\uff0c\u8fd9\u6837\u5c31\u53ef\u4ee5\u8bbf\u95ee\u5bf9\u8c61\u7684\u5c5e\u6027\u548c\u5176\u4ed6\u65b9\u6cd5\u3002<\/p>\n<\/p>\n

\u5f53\u65b9\u6cd5\u88ab\u8c03\u7528\u65f6\uff0cthis \u7684\u503c\u5c31\u4f1a\u52a8\u6001\u5730\u6307\u5411\u8fd9\u4e2a\u65b9\u6cd5\u6240\u5c5e\u7684\u5bf9\u8c61<\/strong>\u3002\u4ee3\u7801\u7684\u7075\u6d3b\u6027\u548c\u53ef\u8bfb\u6027\u5f97\u4ee5\u63d0\u5347\uff0c\u56e0\u4e3a\u4e0d\u9700\u8981\u786c\u7f16\u7801\u5bf9\u8c61\u7684\u5f15\u7528\uff0c\u800c\u662f\u4f9d\u8d56 this \u81ea\u52a8\u6307\u5411\u6b63\u786e\u7684\u5bf9\u8c61\u3002<\/p>\n<\/p>\n

let user = {<\/p>\n
    name: "John",<\/p>\n
    greet() {<\/p>\n
        console.log(`Hello, my name is ${this.name}`);<\/p>\n
    }<\/p>\n
};<\/p>\n
user.greet(); \/\/ \u8f93\u51fa: Hello, my name is John<\/p>\n
<\/code><\/pre>\n<\/p>\n
\u4e8c\u3001\u6784\u9020\u51fd\u6570\u4e2d\u7684 this<\/h3>\n<\/p>\n
\u5728\u6784\u9020\u51fd\u6570\u4e2d\uff0cthis \u8868\u793a\u65b0\u521b\u5efa\u7684\u5bf9\u8c61\u5b9e\u4f8b\u3002\u4f7f\u7528 new \u5173\u952e\u5b57\u8c03\u7528\u6784\u9020\u51fd\u6570\u65f6\uff0cthis \u4f1a\u7ed1\u5b9a\u5230\u65b0\u521b\u5efa\u7684\u5bf9\u8c61\u4e0a\u3002<\/p>\n<\/p>\n
\u8fd9\u4f7f\u5f97\u6784\u9020\u51fd\u6570\u53ef\u4ee5\u521d\u59cb\u5316\u5bf9\u8c61\u5b9e\u4f8b\u7684\u5c5e\u6027\u3002\u6784\u9020\u51fd\u6570\u901a\u5e38\u7528\u4e8e\u521b\u5efa\u5177\u6709\u76f8\u4f3c\u7279\u6027\u4f46\u72ec\u7acb\u5c5e\u6027\u7684\u591a\u4e2a\u5bf9\u8c61<\/strong>\u3002<\/p>\n<\/p>\n
function User(name) {<\/p>\n
    this.name = name;<\/p>\n
    this.greet = function() {<\/p>\n
        console.log(`Hello, my name is ${this.name}`);<\/p>\n
    };<\/p>\n
}<\/p>\n
let user = new User("John");<\/p>\n
user.greet(); \/\/ \u8f93\u51fa: Hello, my name is John<\/p>\n
<\/code><\/pre>\n<\/p>\n
\u4e09\u3001\u4e25\u683c\u6a21\u5f0f\u4e0b\u7684 this<\/h3>\n<\/p>\n
\u5728 JavaScript \u7684\u4e25\u683c\u6a21\u5f0f\uff08strict mode\uff09\u4e0b\uff0c\u51fd\u6570\u4e2d\u7684 this \u503c\u4e0d\u4f1a\u9ed8\u8ba4\u7ed1\u5b9a\u5230\u5168\u5c40\u5bf9\u8c61\uff08\u5728\u6d4f\u89c8\u5668\u4e2d\u662f window\uff09\u3002\u5982\u679c\u6ca1\u6709\u660e\u786e\u8bbe\u7f6e this \u7684\u4e0a\u4e0b\u6587\uff0c\u5b83\u5c06\u4fdd\u6301\u4e3a undefined\u3002<\/p>\n<\/p>\n
\u8fd9\u6709\u52a9\u4e8e\u907f\u514d\u4e0d\u5c0f\u5fc3\u6c61\u67d3\u5168\u5c40\u547d\u540d\u7a7a\u95f4\u7684\u95ee\u9898\uff0c\u56e0\u4e3a\u5728\u4e25\u683c\u6a21\u5f0f\u4e0b\uff0c\u5982\u679c\u5c1d\u8bd5\u8bbf\u95ee this \u5173\u952e\u5b57\u800c\u6ca1\u6709\u6b63\u786e\u7684\u4e0a\u4e0b\u6587\uff0c\u7a0b\u5e8f\u4f1a\u629b\u51fa\u9519\u8bef\u3002<\/p>\n<\/p>\n
function showThis() {<\/p>\n
    'use strict';<\/p>\n
    console.log(this);<\/p>\n
}<\/p>\n
showThis(); \/\/ \u8f93\u51fa: undefined<\/p>\n
<\/code><\/pre>\n<\/p>\n
\u56db\u3001\u5728\u4e8b\u4ef6\u5904\u7406\u4e2d\u7684 this<\/h3>\n<\/p>\n
\u5728 DOM \u4e8b\u4ef6\u5904\u7406\u4e2d\uff0c\u5f53\u4e8b\u4ef6\u76d1\u542c\u5668\u4f5c\u4e3a\u67d0\u4e2a HTML \u5143\u7d20\u7684\u65b9\u6cd5\u6267\u884c\u65f6\uff0cthis \u6307\u5411\u89e6\u53d1\u4e8b\u4ef6\u7684\u5143\u7d20\u3002<\/p>\n<\/p>\n
\u8fd9\u8ba9\u5904\u7406\u4e8b\u4ef6\u53d8\u5f97\u66f4\u7b80\u5355\uff0c\u56e0\u4e3a\u53ef\u4ee5\u8f7b\u677e\u5f15\u7528\u4e8b\u4ef6\u7684\u76ee\u6807\u5143\u7d20\uff0c\u800c\u4e0d\u5fc5\u53e6\u5916\u67e5\u8be2\u6216\u4f20\u9012\u5b83\u3002<\/p>\n<\/p>\n
document.getElementById("myButton").onclick = function() {<\/p>\n
    \/\/ this \u6307\u5411\u89e6\u53d1 click \u4e8b\u4ef6\u7684\u5143\u7d20<\/p>\n
    console.log(this); \/\/ \u8f93\u51fa: <button id="myButton"><\/button><\/p>\n
};<\/p>\n
<\/code><\/pre>\n<\/p>\n
\u4e94\u3001\u7bad\u5934\u51fd\u6570\u4e2d\u7684 this<\/h3>\n<\/p>\n
\u7bad\u5934\u51fd\u6570\u4e0d\u7ed1\u5b9a\u81ea\u8eab\u7684 this\uff0c\u800c\u662f\u6355\u83b7\u5176\u6240\u5904\u4e0a\u4e0b\u6587\u7684 this \u503c\u3002\u8fd9\u610f\u5473\u7740\u5728\u7bad\u5934\u51fd\u6570\u5185\u90e8\uff0cthis \u7684\u503c\u7b49\u4e8e\u5916\u90e8\u4f5c\u7528\u57df\u4e2d\u7684 this\u3002<\/p>\n<\/p>\n
\u8fd9\u7279\u522b\u6709\u7528\u4e8e\u56de\u8c03\u51fd\u6570\u7684\u573a\u666f\uff0c\u4f8b\u5982\u5728 setTimeout \u6216\u4e8b\u4ef6\u5904\u7406\u5668\u4e2d\uff0c\u5b83\u5141\u8bb8\u4f60\u4e0d\u5fc5\u663e\u5f0f\u7ed1\u5b9a\u5916\u90e8\u4f5c\u7528\u57df\u7684 this\u3002<\/p>\n<\/p>\n
function User(name) {<\/p>\n
    this.name = name;<\/p>\n
    setTimeout(() => {<\/p>\n
        console.log(`Hello, my name is ${this.name}`);<\/p>\n
    }, 1000);<\/p>\n
}<\/p>\n
let user = new User("John");<\/p>\n
<\/code><\/pre>\n<\/p>\n
\u516d\u3001\u4f7f\u7528 bind\u3001call \u548c apply \u65b9\u6cd5\u663e\u5f0f\u7ed1\u5b9a this<\/h3>\n<\/p>\n
JavaScript \u63d0\u4f9b\u4e86\u65b9\u6cd5\u5982 bind\u3001call \u548c apply\uff0c\u5141\u8bb8\u5f00\u53d1\u8005\u663e\u5f0f\u5730\u8bbe\u7f6e\u51fd\u6570\u8c03\u7528\u65f6\u7684 this \u6307\u5411\u3002<\/p>\n<\/p>\n
bind \u65b9\u6cd5\u521b\u5efa\u4e00\u4e2a\u65b0\u7684\u51fd\u6570\uff0c\u4f60\u53ef\u4ee5\u4f20\u9012\u4e00\u4e2a\u5bf9\u8c61\u7ed9\u5b83\uff0c\u8fd9\u4e2a\u5bf9\u8c61\u5c06\u7ed1\u5b9a\u5230 this<\/strong>\u3002\u800c call \u548c apply \u7acb\u5373\u6267\u884c\u51fd\u6570\uff0c\u5e76\u5141\u8bb8\u4f20\u5165 this \u503c\u548c\u53c2\u6570\u5217\u8868\u3002<\/p>\n<\/p>\n
function greet() {<\/p>\n
    console.log(`Hello, my name is ${this.name}`);<\/p>\n
}<\/p>\n
let user = {<\/p>\n
    name: "John"<\/p>\n
};<\/p>\n
let greetJohn = greet.bind(user);<\/p>\n
greetJohn(); \/\/ \u8f93\u51fa: Hello, my name is John<\/p>\n
greet.call(user); \/\/ \u8f93\u51fa: Hello, my name is John<\/p>\n
greet.apply(user); \/\/ \u8f93\u51fa: Hello, my name is John<\/p>\n
<\/code><\/pre>\n<\/p>\n
\u4e03\u3001this \u5728\u7c7b\u4e2d\u7684\u7528\u9014<\/h3>\n<\/p>\n
\u5728 ES6 \u5f15\u5165\u7684\u7c7b\u8bed\u6cd5\u4e2d\uff0cthis \u4f9d\u7136\u626e\u6f14\u7740\u91cd\u8981\u89d2\u8272\u3002\u5728\u7c7b\u7684\u65b9\u6cd5\u4e2d\uff0cthis \u6307\u5411\u5b9e\u4f8b\u5bf9\u8c61\uff0c\u4f7f\u5f97\u53ef\u4ee5\u8bbf\u95ee\u5b9e\u4f8b\u7684\u5c5e\u6027\u548c\u5176\u4ed6\u65b9\u6cd5\u3002<\/p>\n<\/p>\n
\u8fd9\u8fdb\u4e00\u6b65\u52a0\u6df1\u4e86\u6a21\u5757\u5316\u548c\u9762\u5411\u5bf9\u8c61\u7f16\u7a0b\uff0c\u4f7f\u4ee3\u7801\u7ed3\u6784\u66f4\u52a0\u6e05\u6670\u3002<\/p>\n<\/p>\n
class User {<\/p>\n
    constructor(name) {<\/p>\n
        this.name = name;<\/p>\n
    }<\/p>\n
    greet() {<\/p>\n
        console.log(`Hello, my name is ${this.name}`);<\/p>\n
    }<\/p>\n
}<\/p>\n
let user = new User("John");<\/p>\n
user.greet(); \/\/ \u8f93\u51fa: Hello, my name is John<\/p>\n
<\/code><\/pre>\n<\/p>\n
\u603b\u4e4b\uff0cthis \u5728 JavaScript \u4e2d\u662f\u4e00\u4e2a\u591a\u9762\u624b\u3002\u5b83\u4e0d\u4ec5\u4f53\u73b0\u4e86\u5bf9\u8c61\u5bfc\u5411\u7f16\u7a0b\u7684\u7279\u6027\uff0c\u4e5f\u4e3a\u51fd\u6570\u7684\u9002\u914d\u6027\u548c\u7075\u6d3b\u6027\u63d0\u4f9b\u652f\u6301\u3002\u4e86\u89e3\u548c\u6b63\u786e\u4f7f\u7528 this \u5173\u952e\u5b57\u5bf9\u4e8e\u7f16\u5199\u9ad8\u6548\u4e14\u53ef\u7ef4\u62a4\u7684 JavaScript \u4ee3\u7801\u81f3\u5173\u91cd\u8981\u3002<\/p>\n<\/p>\n
\u76f8\u5173\u95ee\u7b54FAQs\uff1a<\/strong><\/h2>\n
1. \u4ec0\u4e48\u60c5\u51b5\u4e0b\u53ef\u4ee5\u4f7f\u7528 JavaScript \u4e2d\u7684 this?<\/strong><\/p>\n
\u5728 JavaScript \u4e2d\uff0cthis \u5173\u952e\u5b57\u7684\u7528\u9014\u6709\u5f88\u591a\u3002\u5e38\u89c1\u7684\u4f7f\u7528\u573a\u666f\u5305\u62ec\u5728\u5bf9\u8c61\u7684\u65b9\u6cd5\u4e2d\u5f15\u7528\u5bf9\u8c61\u672c\u8eab\u3001\u5728\u6784\u9020\u51fd\u6570\u4e2d\u5f15\u7528\u65b0\u521b\u5efa\u7684\u5b9e\u4f8b\u5bf9\u8c61\u4ee5\u53ca\u5728\u4e8b\u4ef6\u5904\u7406\u51fd\u6570\u4e2d\u5f15\u7528\u89e6\u53d1\u4e8b\u4ef6\u7684\u5143\u7d20\u3002this \u7684\u4f7f\u7528\u53ef\u4ee5\u4f7f\u4ee3\u7801\u66f4\u52a0\u7075\u6d3b\u548c\u53ef\u590d\u7528\u3002<\/p>\n
2. \u5982\u4f55\u6b63\u786e\u4f7f\u7528 JavaScript \u4e2d\u7684 this?<\/strong><\/p>\n
\u4f7f\u7528 this \u5173\u952e\u5b57\u65f6\uff0c\u9700\u8981\u6ce8\u610f\u4e00\u4e9b\u7ec6\u8282\u3002\u9996\u5148\uff0c\u8981\u6ce8\u610f\u5728\u51fd\u6570\u4e2d\u4f7f\u7528 this \u524d\uff0c\u786e\u4fdd\u51fd\u6570\u88ab\u4f5c\u4e3a\u5bf9\u8c61\u7684\u65b9\u6cd5\u8c03\u7528\uff0c\u8fd9\u6837 this \u624d\u4f1a\u6307\u5411\u6b63\u786e\u7684\u5bf9\u8c61\u3002\u5176\u6b21\uff0c\u8981\u6ce8\u610f\u5728\u7bad\u5934\u51fd\u6570\u4e2d\uff0cthis \u7684\u6307\u5411\u4e0d\u662f\u52a8\u6001\u53d8\u5316\u7684\uff0c\u800c\u662f\u7531\u51fd\u6570\u5b9a\u4e49\u65f6\u6240\u5728\u7684\u4e0a\u4e0b\u6587\u51b3\u5b9a\u7684\u3002\u6700\u540e\uff0c\u5f53 this \u7528\u4e8e\u6784\u9020\u51fd\u6570\u65f6\uff0c\u53ef\u4ee5\u4f7f\u7528 new \u5173\u952e\u5b57\u6765\u521b\u5efa\u65b0\u7684\u5b9e\u4f8b\u5bf9\u8c61\uff0c\u5e76\u4e14 this \u4f1a\u6307\u5411\u8fd9\u4e2a\u65b0\u7684\u5bf9\u8c61\u3002<\/p>\n
3. \u662f\u5426\u53ef\u4ee5\u624b\u52a8\u6539\u53d8 JavaScript \u4e2d this \u7684\u6307\u5411\uff1f<\/strong><\/p>\n
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