解構(gòu)賦值：按照一個(gè)數(shù)據(jù)值的結(jié)構(gòu)，快速解析獲取到其中的內(nèi)容

• 數(shù)組解構(gòu)賦值

  1.想要幾個(gè)就幾個(gè)

  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
  
  // 省略賦值
  let [e, , f] = ary;
  console.log(e,f);      // 12 34
  

  2.設(shè)置默認(rèn)值也行（默認(rèn)解構(gòu)）

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

  3.不僅可以解構(gòu)成單個(gè)值，還可以返回個(gè)數(shù)組

  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.互換位置更加方便

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

• 對(duì)象解構(gòu)賦值

  1.對(duì)象解構(gòu)賦值默認(rèn)情況下要求：左側(cè)變量名和對(duì)象中的屬性名一致才可以

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

  2.給不存在的屬性設(shè)置默認(rèn)值

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

  3.給解構(gòu)的屬性名起別名作為需要使用的變量

  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