js小白模拟系列_模拟bind

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Function.prototype.myBind = function (context) {
      var context = context || window;
     	var args = [].slice.call(arguments,1);//第一位是 context 其余的要传给fn
     	var fn = this;
     	return function () {
     		var _args = [].slice.call(arguments);
     		return fn.apply(context,args.concat(_args));
     	}
     }
     
       var name = 'window';
       var obj = {name : 'obj'}
       function test (a,b,c,d) {
       	console.log(this.name);
       	console.log(a,b,c,d);
       }
       
       var newTest = test.myBind(obj,'a');
       newTest('b','c','d');

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 Function.prototype.myBind = function (context) {
      var context = context || window;
     	var args = [].slice.call(arguments,1);//第一位是 context 其余的要传给fn
     	var fn = this;
     	function temp () {};
     	temp.prototype = fn.prototype;
     	F.prototype = new temp();
     	function F () {
     		var _args = [].slice.call(arguments);
     		return fn.apply(this instanceof temp ? this : context,args.concat(_args));
     	}
//这里涉及两个知识点,一个是继承,这里用的是圣杯模式
//一个是new  . 没有new this指向 window , 如果new this指向 F 构造出来的实例.
     	return F
     }
     
       var name = 'window';
       var obj = {name : 'obj'}
       
       test.prototype.age = 18;
       function test (a,b,c,d) {
        this.name = 'mike';
       	console.log(this.name);
       	console.log(a,b,c,d);
       }
       
       var newTest = test.myBind(obj,'a');
       var obj = new newTest('b','c','d');//mike,a,b,c,d
       console.log(name);// window
       console.log(obj.age);//18
       console.log(obj.name);//mike