手写call、apply、bind

四季予你662024-09-13 9:37

一、手写call

javascript 复制代码

const person = {name:'zhangsan'}
function foo(numA,numB){
    console.log(this)
    console.log(numA,numB)
    return numA + numB
}

// 手写call
Function.prototype.mycall = function(thisArg,...args){ // 手写call
    const key = Symbol('key') // 唯一标识符
    thisArg[key] = this // 绑定this
    const res = thisArg[key](...args) // 展开参数
    delete thisArg[key] // 清除
    return res
}

const res = foo.mycall(person,1,2) // thisArg = person
console.log(res)

二、手写apply

javascript 复制代码

Function.prototype.myapply = function(thisArg,args){
    const key = Symbol('key')
    thisArg[key] = this
    const res = thisArg[key](...args)
    delete thisArg[key]
    return res
}

const person = {name:'zhangsna'}
function foo(numA,numB){
    console.log(this)
    console.log(numA,numB)
    return numA+numB
}
const res = foo.myapply(person,[1,2])
console.log(res)

三、手写bind

javascript 复制代码

// 手写bind
Function.prototype.myBind = function(thisArg,...args){
    // 返回新函数
    return (...reArgs)=> this.call(thisArg,...args,...reArgs)
}

const person = {name:'zhangsan'}
function foo(numA,numB,numC,numD){
    console.log(this)
    console.log(numA,numB,numC,numD)
    return numA + numB + numC + numD
}
const bindFunc = foo.myBind(person,1,2)
const res = bindFunc(3,4)
console.log(res)