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,不同於传入参数型态,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