es变量赋值的新写法
let a=1;
let b=2;
let c=3;
let d=4;
lat [a,b,c]=[1,2,3]
不完全解构、
let [x,y]=[1,2,3] // x=1; y=2;
报错的几种情况：
let [foo]=1;
let [foo]=false;
let [foo] = NaN;
let [foo] = undefined;
let [foo] = null;
let [foo] = {}
默认值
let [x=1, y=x] = []// 1,1
let [x=1, y=x]=[2] // 2, 2
let [x=1, y=x]=[1,2] //1,2
let [x=y, y=1] = []; // error
对象解构，对象解构没有秩序
let {foo, bar} = {foo:"aaa", bar:"bbb"} // aaa, bbb
let obj={first: 'hello', second:'word'}
let {first:1, second:2} = obj; // first: hello; second: world
//嵌套解构
let obj = {
p:[
'hello',
{
y:'world'
}
]
}
let {p:[x, {y}]} = obj;
字符串解构
[a,b,c,d,e,f] = 'hello'
函数解构
[[1,2]. [3,4]].map(([a,b])=> a+b); // [3, 7]
用途
-
值交换
let x=1; let y=2; [x,y]=[y,x] -
从函数中返回多个值
function example(){ return {1,2,3} } let [a,b,c]=example(0;) -
提取json
let jsonData = { id:42, status:"OK", data:[876, 5309], } let {id, status, data, number} = jsonData; -
map的遍历
var map=new Map() map.set('fist','hello'); map.set('second','world'); for(let [key, value] of map){ console.log(key, value); } // 只遍历key for(let [key] of map){ console.log(key); } // 只遍历value for(let [, value] of value){ console.log(value); }
