浏览器环境
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>this</title>
</head>
<body>
<script>
var age = 100
var rick = {
age: 30,
name: 'Rick',
grow() {
console.log(`I am ${this.name}, I am ${this.age}`) // age: 30
setTimeout(function() {
console.log(`I am ${this.age}`) // 100
console.log(`I am ${window.age}`) // 100
console.log(`I am ${age}`) // 100
console.log(window === this) // true
}, 100)
}
}
rick.grow()
function testThis(param) {
console.log(param + '. this === window => ' + (this === window))
}
testThis(1) // 作为一个函数的话 this指向global，浏览器环境下就是window
new testThis(2) // 作为一个对象的话 this指向对象
</script>
</body>
</html>
node环境
// let age = 100;
age = 100
let rick = {
age: 30,
name: 'Rick',
grow() {
// console.log(`I am ${this.name}, I am ${this.age}`) // age: 30
setTimeout(function() {
console.log(`I am ${this.age}`) // 使用bind(this) age: 30. 否则this函数自身的this
// console.log(this)
// for (let k in this) {
// console.log(k)
// }
}.bind(this), 1001)
}
}
// rick.grow()
// 数组复制
let a = [1, 2]
let b = [...a]
console.log(b)
// 对象复制
let user = {
name: 'Jame'
}
let c = Object.assign({}, user)
console.log(c)
let d = {...user}
console.log(d)
// 数组转函数参数
function test(a, b) {
console.log(`a: ${a}, b: ${b}`)
console.log(`2.this => ${this}`)
}
console.log(test(...a))
console.log(test.apply(null, a)) // apply的作用
console.log(`1.this => ${this}`)