箭头函数vs匿名函数 

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<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        // 1.在箭头函数里没有自己的 this 和 arguments
        let a = {
            foo: 42,
            bar: () => {
                // console.log(this);
                // console.log(arguments); // 报错
                console.log('Inside `bar`:', this.foo);
                console.log('Inside `bar`:', a.foo);
                /* Inside `bar`: undefined
                Inside `bar`: 42 */
            },
        }
        a.bar();

        // 2.在匿名函数里有
        let b = {
            foo: 42,
            bar: function() {
                console.log(this); // {foo: 42, bar: ƒ}bar: ƒ ()foo: 42__proto__: Object
                console.log(arguments); // Arguments [callee: ƒ, Symbol(Symbol.iterator): ƒ]callee: ƒ ()arguments: nullcaller: nulllength: 0name: "bar"prototype: {constructor: ƒ}__proto__: ƒ ()[[FunctionLocation]]: 箭头函数.html:27[[Scopes]]: Scopes[2]length: 0Symbol(Symbol.iterator): ƒ values()__proto__: Object
                console.log('Inside `bar`:', this.foo); // Inside `bar`: 42
            },
        }
        b.bar();
    </script>
</body>
</html>

　　

箭头函数无法 new

  1. 箭头函数无法 new
> new (() => {});
TypeError: (intermediate value) is not a constructor
> var x = () => {};
> new x();
TypeError: x is not a constructor
  1. 匿名函数可以
> new (function() {});
{}
> let f = function() {};
> new f();
f {}
posted @ 2021-01-04 11:26  小白咚  阅读(418)  评论(0)    收藏  举报