手写apply、call、bind

apply

    Function.prototype.myApply = function(context){
        context = context || window
        context.fn = this
        var res 
        if(arguments[1]){
            res = context.fn(...arguments[1])
        }else{
            res = context.fn()
        }
        delete context.fn
        return res 
    }

//测试
    let foo = {
        alue: 1
    }
    function bar(name, age) {
        console.log(name)
        console.log(age)
        console.log(this.value)
    }
    bar.myApply(foo, ['kevin', 18]) // kevin 18 1  

call

    Function.prototype.myCall = function(context){
        context = context || window
        context.fn = this
        var args = Array.from(arguments).slice(1)
        var res
        if(arguments.length>1){
            res = context.fn(...args)
        }else{
            res = context.fn()
        }
        delete context.fn
        return res 
    }

//测试
    let obj = {
        name: 'xxx'
    };
    function test(){
        console.log('arguments=',arguments); // Arguments(2) [1, 2, callee: ƒ, Symbol(Symbol.iterator): ƒ]
        console.log('this=',this); // {name: "xxx", fn: ƒ}
    }
    test.myCall(obj,1,2);

bind

    Function.prototype.myBind = function(context){
        var self = this
        var args = Array.prototype.slice.call(arguments,1)
        var F = function(){}
        var fBind = function(){
            var bindArgs = Array.prototype.slice.call(arguments)
            self.apply(this instanceof F ? this:context,args.concat(bindArgs))
        }
        F.prototype=this.prototype
        fBind.prototype=new F()
　　　　　return fBind
    }

//测试
    let obj1 = {
        name: 'xxx'
    };
    function test1(name,age){
        console.log('arguments=',arguments);//Arguments(2) [22, 33, callee: ƒ, Symbol(Symbol.iterator): ƒ]
        console.log('this=',this); // {name: "xxx"}
    }
    let f = test1.myBind(obj1,22,33)
    f() //需要手动执行