ES6解构赋值

1. let {foo:fzz} = {foo:"aa"}//fzz = aa先取出foo然后给fzz
2. 解构赋值的默认:let [foo = true] = [];let {foo = true} = {}
3. 数组嵌套赋值:
   a. let [f,{s}] = [1,{s:"aa"}]//f = 1,s = "aa"
   b. let {p,p:[{f}]} = {p:[{f:"aa"}]};//p = [{f:"aa"}],f=aa p是模式匹配
4. 直接解构赋值和…的区别:
   a. let [a,...res] = [1]//a=1,res = []
   b. let [a,b] = [1]//a = 1,b = undefined
   c. let {a,...res} = {a:"aa"} // a = "aa",res = {}
   d. let {a,b} = {a:"aa"} // a = "aa",b = undefined
5. 解构赋值的默认值如果是表达式，那么该函数只有在用到的时候才执行
   a. let {a,b=function(){return "bb"}()} = {a:"aa"}//a=aa,b=bb
6. 解构赋值的默认值如果是变量，那么被引用的变量必须在前面
   a. let {a,b=a} = {a:"aa"}//a = aa,b=aa
7. 数组本质是特殊的对象，因此可以对数组进行对象属性的解构:
   a. let {0:first,1:second} = [1,2]//first = 1;second = 2
8. 字符串的解构赋值: 字符串被被转成了类似数组的东西
   a. let [first,second] = "hello"//first = h,second = e
   b. let {0:first,1:second,length:len} = "hello"//len = 5
9. 交换变量的值:
   a.let x = 1;let y = 2;[x,y] = [y,x]