es6--解构赋值-用途

// 1:交换变量的值

let a = 1; let b = 2;

console.log(a,b);

[a,b] = [b,a];

console.log(a,b)

// 2:函数返回多个值

function fn (){

return [1,2,3]

}

let [a,b,c] = fn()

console.log(a,b,c)

function fn2(){

return {

a:1,

b:2

}

}

let {a:d,b:e} = fn2()

console.log(d,e)

// 3:函数参数的定义

function fn([a,b]){return a+b}

console.log(fn([1,2]))

function fn2({a,b}){return a+b}

console.log(fn2({b:1,a:2}))

// 4:提取json数据

let obj = {

a:2,

b:4

}

let {a,b} = obj

// 5:函数参数的默认值可以直接在（）内定义而不必在函数内写

// 6:便利map结构

let map = new Map()

map.set('first','hello')

map.set('second','world')

for(let [key,val] of map){

console.log(key+' is '+val)

}

for(let [,val] of map){

console.log(val)

}

for(let [key] of map){

console.log(key)

}

// 7:引入模块

// data里数据

const data = {

a:1,

b:2

}

import {data} from 'url/data'