Js解构赋值的应用

function add([a, b]){
    return a + b;
}
console.log(add([1, 2]));  //控制台输出3

function add(a, b){
    return a + b;
}
console.log(add(1, 2));  //控制台输出3

function move({x = 0, y = 0} = {}) {
  return [x, y];
}
move({x: 3, y: 8}); // [3, 8]
move({x: 3}); // [3, 0]
move({}); // [0, 0]
move(); // [0, 0]

  function guoguo(youname="郭郭",youage=18) {
      console.log("youname is "+youname+" youage is "+youage);
  }

  guoguo(); //没有传参数，两个参数都取默认值，控制台输出 youname is 郭郭 youage is 18
  guoguo("郭大剑"); //传了一个参数，第二个参数取默认值，控制台输出 youname is 郭大剑 youage is 18
  guoguo("郭大剑",39); //传了二个参数，两个参数默认值都不起作用，控制台输出 youname is 郭大剑 youage is 39

  function move({x = 0, y = 0}) {
    return [x, y];
  }
  
  console.log( move({x: 3, y: 8})); // [3, 8]
  console.log( move({x: 3})); // [3, 0]
  console.log( move({})); // [0, 0]
  console.log( move()); //TypeError: Cannot read property 'x' of undefined  无法解构，导至引用x变量报错。

  //此处谢谢阮一峰兄弟，这些例子我都是抄他的
  //快速从返回的数组中取数
  function example() {
    return [1, 2, 3];
  }
  let [a, b, c] = example();

  //快速从jsON中提取数据
  let jsonData = {
    id: 42,
    status: "OK",
    data: [867, 5309]
  };
  let { id, status, data} = jsonData;

  //遍历map
  const map = new Map();
  map.set('first', 'hello');
  map.set('second', 'world');
  
  for (let [key, value] of map) {
    console.log(key + " is " + value);
  }  
  
  //获取键
  for (let [key] of map) {
    // ...
  }
  
  //获取键值
  for (let [,value] of map) {
    // ...
  }