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手写bind220318.html

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 * @FilePath: \geyao\geyao\手写call220315.html
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<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>手写call</title>
</head>

<body>
  <script>
    Function.prototype.mybind = function (target) {


      console.log(arguments,"arguments")
      var args = [].slice.call(arguments, 1); //获取bind时传入的绑定实参
      console.log(args,"args")
      var self = this; //要bind的函数
      console.log(this,"this")
      var temp = function(){};//作为中间函数,用于实现继承
          //target不存在this默认window，当new调用时无需修改this指向
    var obj = this instanceof temp ? this : (target || window);
      var _fn = function () {
        var _args = [].slice.call(arguments, 0); //新函数执行时传递的实际参数
        console.log(_args,"_args")
        console.log(args.concat(_args),"args.concat(_args)")
        return self.apply(obj, args.concat(_args));
      }
         //让中间函数的原型指向，要bind函数的原型
    temp.prototype = self.protoype;
    //让新函数的原型指向中间temp的对象，然后找到要bind函数的原型
    _fn.prototype = new temp();//这样新函数生成的对象的constructor就能找到旧的函数
      return _fn
    }


    var name = 'fangfang';
    var obj = {
      name: 'geyao'
    };

    function fn(a, b, c) {
      console.log(a + b + c + this.name);
      return a + b + c + this.name
    };
    fn.mybind(obj)(1,2,3); // 我的老婆是geyao
  </script>
</body>

</html>