你或许不知道的ES6解构赋值

相信大家对解构赋值并不陌生：
阮大佬ECMAScript 6 入门
里面有讲七种用途，用得最多莫过于json数据处理

json数据处理

let jsonData = {
  id: 42,
  status: "OK",
  data: [867, 5309]
};

let { id, status, data: number } = jsonData;

console.log(id, status, number);
// 42, "OK", [867, 5309]

当然变换变量的值，也是用得较多的。

交换变量的值

let x = 1;
let y = 2;

[x, y] = [y, x];

let x3 = "a";
let y3 = "b";
let z3 = "c";
[x3,y3,z3] = [z3,y3,x3];
console.log(x3,y3,z3);//c,b,a

for…of中使用

const arrC = ["a", "b"];
for(const [index, element] of arrC.entries()){
    console.log(index,element);
}
//0 "a"
//1 "b"

还可以对象解构原始值(字符长度等。。)

const {length: len} = "abc";
console.log(len);//3

对象的剩余属性构造

const objA = {a: 1, b: 2, c: 3};
const {a:propValue, ...remaining}= objA;
console.log(propValue,remaining);//1 {b: 2, c: 3}

remaining被分配一个对象，该对象具有在模式中未提及其键的所有数据属性。

数组的剩余属性构造

const [xx,yy,...rest] = ["a","b","c","d"];
console.log(xx,yy,rest);//a b ["c","d"]

rest被分配一个对象，该数组具有在模式中未提及的所有元素。

数组解构：返回数组的操作

const  [,year,month,day] = /^([0-9]{4})-([0-9]{2})-([0-9]{2})$/.exec('2999-12-31')
console.log(/^([0-9]{4})-([0-9]{2})-([0-9]{2})$/.exec('2999-12-31'));//["2999-12-31", "2999", "12", "31", index: 0, input: "2999-12-31", groups: undefined]
console.log(year,month,day);//2999 12 31

处理函数返回结果

function findElement(arr, predicate) {
   for (let index=0; index < arr.length; index++) {
        const value = arr[index];
        if (predicate(value)) {
            return { value, index };
        }
    }
    return { value: undefined, index: -1 };
}
const arrD = [7, 8, 6];
// const {value, index} = findElement(arrD, x => x % 2 === 0);//可以一起输出，也可以单个解构输出
const {value} = findElement(arrD, x => x % 2 === 0);
const {index} = findElement(arrD, x => x % 2 === 0);
console.log(value,index);

参考文献：JavaScript for impatient programmers