ES6新特性四：變量的解構(gòu)賦值實例

//① 可以從數(shù)組中提取值，按照對應(yīng)位置，對變量賦值
var [a, b] = [1, 2]; //a = 1;b = 2
//② 下面是一些使用嵌套數(shù)組進行解構(gòu)
var [d, [[c], f]] = [1, [[2], 3]];
var [,,third] = ["foo", "bar", "baz"];//third = "baz"
var [head, ...tail] = [1, 2, 3, 4];//head = 1;tail = [2, 3, 4]
//③不完全結(jié)構(gòu)
var [x, y] = [1,2,6]; //x = 1;y = 2
//④ 解構(gòu)賦值允許指定默認(rèn)值
var [foo = true] = []; //foo = true
var [x, y='b'] = ['a'] // x='a', y='b'
var [x, y='b'] = ['a', undefined] // x='a', y='b'
//⑤ 解構(gòu)不成功，變量的值就等于undefined
var [a6, a7] = [1]; //a7 = undefined

[a, b, c] = new Set(["a", "b", "c"])
console.log(a) // "a"

//對象的屬性沒有次序，變量必須與屬性同名，才能取到正確的值
var { x, y } = { x: "aaa", y: "bbb" };//x = aaa, y = bbbb
var { c } = { a: "aaa", b: "bbb" }; // c = undefined
//嚴(yán)格遵守變量名與屬性同名
var { d: e } = { d: "aaa", f: "bbb" }; //e = aaa
//指定默認(rèn)值
var {x, y = 5} = {x: 1};// x = 1,y = 5

var map = new Map();
map.set('first', 'hello');
map.set('second', 'world');
//獲取鍵值對
for (let [key,value] of map) {
  console.log(key + " is " + value);
}
// 獲取鍵名
for (let [key] of map) {
  console.log(key);
}
// 獲取值
for (let [,value] of map) {
  console.log(value);
}