bind, call, apply

在未经过绑定的this会指向Windows

Bind

使用Bind会return 一个function

let Dennis = {    name: "Dennis",    age: 22}function hello() {    console.log(this) //指向Window    console.log(this.age)}hello() //undefined

所以这边使用bind method绑定在指定的物件身上

let Dennis = {    name: "Dennis",    age: 22}function hello() {    console.log(this) //指向Dennis    console.log(this.age) //22}const Hello = hello.bind(Dennis)Hello()

Call

使用call 会直接执行,所以不需要变数接住function再执行

let Dennis = {    name: "Dennis",    age: 22}function hello() {    console.log(this) //指向Dennis    console.log(this.age) //22}hello.call(Dennis)

并且 call可以传入参数

let Dennis = {    name: "Dennis",    age: 22}function hello(parameter) {    console.log(`My name is ${this.name} phonenumber is ${parameter}`)}hello.call(Dennis,) //My name is Dennis phonenumber is undefined

加入参数

let Dennis = {    name: "Dennis",    age: 22}function hello(parameter) {    console.log(`My name is ${this.name} phonenumber is ${parameter}`)}hello.call(Dennis, "0900123123") //My name is Dennis phonenumber is 0900123123

Apply

apply跟call几乎一样,不同于传入参数型态,若是array使用apply,string等等使用call

let c = ["000000"]let Dennis = {    name: "Dennis",    age: 22}function hello(parameter) {    console.log(`My name is ${this.name} phonenumber is ${parameter}`)}hello.apply(Dennis, c) //My name is Dennis phonenumber is 000000