前言

大家好我是歌谣上节课我们已经说过了关于手写apply和手写call的讲解
这节课我们继续来进行手写bind的讲解

bind演示

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>手写bind.html</title>
</head>
<body>
    <script>
         var geyao = {
            name: "geyao",
            show() {
                console.log(this, "this")
                console.log(` 我是${this.name}`)
            }
        }
        var fangfang = {
            name: "fangfang"
        }

        let fn=geyao.show.bind(fangfang)
        fn()

    </script>
</body>
</html>

运行结果

在这里插入图片描述

分析

核心的功能就是第一会改变this的指向第二函数不会立刻执行

代码

 var geyao = {
            name: "geyao",
            show() {
                console.log(this, "this")
                console.log(` 我是${this.name}`)
            }
        }
        var fangfang = {
            name: "fangfang"
        }
        Function.prototype.myBind = function (content, args) {
            
            let fn = Symbol('geyao')
            fn = this
            return function Fn() {
                // 这里arguments的作用是拿到Fn中传入的参数
                return fn.call(content, args)
            }
        }

        let fn = geyao.show.myBind(fangfang)
        fn()

运行结果

在这里插入图片描述

思考

这里还需要对new bind进行一个实现不是上述所说的这么简单

  function geyao() {
            this.fangfang = 'fangfang';
        }
        var geyaoFoo = geyao.bind();
        var obj = new geyaoFoo();
        console.log(obj.fangfang);

运行结果

在这里插入图片描述

最终代码

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>手写bind2.html</title>
</head>
<body>
    <script>
        Function.prototype.myBind = function (context, ...args) {
            let geyao = Symbol('geyao')
            geyao = this
            return function Fangfang() {
                if (this instanceof Fangfang) {
                    return new geyao(...args, ...arguments)
                }
                return geyao.call(context, arguments)
            }
        }
        function geyao() {
            this.fangfang = 'fangfang';
        }
        var geyaoFoo = geyao.myBind();
        var obj = new geyaoFoo();
        console.log(obj.fangfang);
    </script>
</body>

</html>