瞅瞅ES6多好玩——解构赋值篇

解构赋值：按照一个数据值的结构，快速解析获取到其中的内容

• 数组解构赋值

  1.想要几个就几个

  let ary = [12, 23, 34, 45, 56];
  let [a, b, c] = ary;
  console.log(a, b, c);  // 12 23 34
  let [d] = ary;
  console.log(d);        // 12
  
  // 省略赋值
  let [e, , f] = ary;
  console.log(e,f);      // 12 34
  

  2.设置默认值也行（默认解构）

  let ary = [12];
  let [a, b = 0] = ary;
  console.log(a, b);     // 12 0
  

  3.不仅可以解构成单个值，还可以返回个数组

  let ary = [12, 23, 34, 45, 56];
  let [a, ...b] = ary;
  console.log(a, b);         // 12 [23,34,45,56]
  let [a, ...b, c] = ary;    // SyntaxError: Rest element must be last element
  

  4.互换位置更加方便

  let a = 12,
      b = 13;
  [a, b] = [b, a];
  console.log(a, b);    // 13 12
  

• 对象解构赋值

  1.对象解构赋值默认情况下要求：左侧变量名和对象中的属性名一致才可以

  let obj = {name: 'xxx', age: 25, sex: 0};
  let {name, age} = obj;
  console.log(name, age);  // "xxx" 25
  

  2.给不存在的属性设置默认值

  let obj = {name: 'xxx', age: 25, sex: 0};
  let {friend = 0} = obj;
  console.log(friend);    // 0 
  

  3.给解构的属性名起别名作为需要使用的变量

  let obj = {name: 'xxx', age: 25, sex: 0};
  let {age: ageAA} = obj;
  console.log(age);    // Uncaught ReferenceError: age is not defined
  console.log(ageAA);  // 25