ES6 变量解构赋值的用途

• 数组

let [a, b, c] = [1, 2, 3];let [foo = true] = [];

• 对象

let { foo, bar } = { foo: "aaa", bar: "bbb" };let { foo: baz } = { foo: 'aaa', bar: 'bbb' };

• 字符串

const [a, b, c, d, e] = 'hello';

• 函数

function add([x, y]){ return x + y;}add([1, 2]); // 3

[[1, 2], [3, 4]].map(([a, b]) => a + b);

function move({x = 0, y = 0} = {}) { return [x, y];}move({x: 3, y: 8}); // [3, 8]

解构赋值的用途

• 交换变量的值

let x = 1;let y = 2;[x, y] = [y, x];

• 从函数返回多个值

function example() { return [1, 2, 3];}let [a, b, c] = example();

function app() { return { foo: 1, bar: 2 };}let { foo, bar } = app();

• 函数参数的定义

function f([x, y, z]) { … }
f([1, 2, 3]);

function g({ x, y, z }) { … }
g({ z: 3, y: 2, x: 1 });

• 提取json数据

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

• 函数参数的默认值

jQuery.ajax = function(url, { async = true, beforeSend = function() {}, cache = true, complete = function() {}, crossDomain = false, global = true, // ... more config}) { // ... do stuff};

• 遍历Map结构

var map = new Map();
map.set(‘first’, ‘hello’);
map.set(‘second’, ‘world’);

for (let [key, value] of map) {
console.log(key + ‘is’ + value);
}
for (let [key] of map) {
console.log(key);
}
for (let [, value] of map) {
console.log(value);
}

• 输入模块的指定方法

const { SourceConsumer, sourceNode } = require('source-map');