对象解构

解构本质上是匹配，只要等号两边的模式相同，左边的变量就会被赋予对应的值。

解构的目标需为可遍历对象

可以重新命名，可以默认值

const obj = {
	name:'A',
    age:18,
    address:'B'
}
const {name,age,address} = obj;
console.log(name)//'A'

let [a = 3, b = a] = [];     // a = 3, b = 3
let [a = 3, b = a] = [1];    // a = 1, b = 1
let [a = 3, b = a] = [1, 2]; // a = 1, b = 2

用于函数参数默认值

function drawES5Chart(options) {
  options = options === undefined ? {} : options;
  var size = options.size === undefined ? 'big' : options.size;
  var cords = options.cords === undefined ? { x: 0, y: 0 } : options.cords;
  var radius = options.radius === undefined ? 25 : options.radius;
  console.log(size, cords, radius);
  // now finally do some chart drawing
}

drawES5Chart({
  cords: { x: 18, y: 30 },
  radius: 30
});

解构语法别名是冒号，赋值是等号

使用解构：

function drawES6Chart({size='big',cords={x:10,y:30},radius:30}={})
{
	console.log(size,cords,radius)
}
drawES5Chart({
  cords: { x: 18, y: 30 },
  radius: 30
});

交换变量的值

let x = 4
let y = 6
[x,y] = [y,x]

JS对象解构

对象解构