Destructuring assignment
    解构赋值将属性和值从对象或数组中取出，赋值给其他变量

    1. var a, b, rest;
    2. var arr = [1, 2, 3, 4]
    4. [a, b, ...rest] = arr;
    5. console.log(a);  // 1
    6. console.log(b);  // 2
    7. console.log(rest);  // [3, 4]
    9. ({a, b, ..rest}) = {a: 1, b: 2, c: 3, d:4});
    10. console.log(a);  // 1
    11. console.log(b);  // 2
    12. console.log(rest);  // {c: 3, d: 4}
    14. var [x, y] = [1, 2];
    15. console.log(x); // 1
    16. console.log(y); // 2

    设置默认值

    1. var [a = 1, b = 2] = [3];
    2. a;  // 3
    3. b;  // 2
    5. var {c = 1, d = 2} = {c: 3}

    交换变量

    1. var a = 1;
    2. var b = 3;
    4. [a, b] = [b, a];
    5. console.log(a); // 3
    6. console.log(b); // 1

    解析从函数返回的数组

    1. fn = () => [1, 2];
    3. var [a, b] = fn();
    4. a;  // 1
    5. b;  // 2

    忽略函数的返回值

    1. fn = () => [1, 2, 3]
    2. var [a, , b] = fn();
    4. a // 1
    5. b // 3

    解构对象，改变变量名，设置默认值

    1. var {a:aa = 1, b:bb = 2} ={a: 3}
    3. aa  // 3
    4. bb  // 2