手写new, bind, call, apply

myNew

function myNew(constructor, ...args) {
    let obj = {}
    obj.__proto__ = constructor.Protorype
    constructor.call(obj, ...args)
    return obj
}

myBind

Function.prototype.myBind = function(obj=window, ...outerArgs){
    let _this = this
    return function(...innerArgs){
        _this.call(obj, ...outerArgs.concat(innerArgs)) // call接收的是多个参数 apply接收的是数组
    }
}

myCall

Function.prototype.myCall = function(obj=window, ...args){
    obj.f = this
    const res = obj.f(...args)
    delete obj.f
    return res
}

myApply

Function.prototype.myApply = function(obj=window, args){ // apply传入数组
    obj.f = this
    const res = obj.f(...args)
    delete obj.f
    return res
}

ref

【前端面试】new, bind, call, apply 手写