es 解构

1⃣️ 数组解构

let arr = [1, 2, 3]
let [a, b, c] = arr;
console.log(a, b, c) // 1 2 3

let arr = [1, 2, [3, 4]]
let [a, b, c] = arr;
console.log(a, b, c) // 1 2 [3,4]

let arr = [1, 2, [3, 4]]
let [a, b, [c, d]] = arr;
console.log(a, b, c, d) // 1 2 3,4

let [a, b, c, d] = [1, 2, [3, 4]];
console.log(a, b, c, d) // 1 2 [3, 4] undefined

let [a, b, c, d = 5] = [1, 2, [3, 4]];
console.log(a, b, c, d) // 1 2 [3, 4] 5

let [a, b, c, d = 5] = [1, 2, [3, 4], 6];
console.log(a, b, c, d) // 1 2 [3, 4] 6

2⃣️对象解构

let user = {
    name: 'kiw',
    age: '18'
}
let {
    name,
    age
} = user
console.log(name, age)  // kiw 18

别名

let user = {
    name: 'kiw',
    age: '18'
}
let {
    name: uname,
    age: uage
} = user
console.log(uname, uage)  // kiw 18

3⃣️字符串解构

let str = 'imooc'
let [a, b, c, d, e] = str;
console.log(a, b, c, d, e); // i m o o c

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作用
1利用解构实现 默认值 和快速赋值/传值
2 快速提取对象/数组中的一些属性 减少代码量