ES6解构赋值的用途

1、交换变量的值

        //ES5
    console.log("ES5:");
    var a = 100;
    var b = 200;
    var temp;
    temp = a;
    a = b;
    b = temp;
    console.log("a = " + a);    //a = 200
    console.log("b = " + b);    //b = 100

    //ES6
    var x = 100;
    var y = 200;
    [x, y] = [y, x];
    console.log("交换后：");
    console.log("x = " + x);    //x = 200
    console.log("y = " + y);    //y = 100

2、从函数返回多个值_返回一个数组

        function fun () {
        return [1, 2, 3];
    };
    var [x, y, z] = fun();
    console.log(x);    //1
    console.log(y);    //2
    console.log(z);    //3    

3、从函数返回多个值_返回一个对象

    function fun () {
      return {
          id  : "007",
          name: "Conan",
          age : 28
      };
    };

    var { id, name, age } = fun();
    console.log(id);    //007
    console.log(name);    //Conan
    console.log(age);    //28

    var { id: person_id, name: person_name, age: person_age } = fun();
    console.log(person_id);        //007
    console.log(person_name);    //Conan
    console.log(person_age);    //28    

4、函数参数的定义

        // 参数是一组有次序的值
    function fun ([x, y, z]) {
        //x = 100;
        //y = 200;
        //z = 300;
    };
    fun([100, 200, 300]);

    // 参数是一组无次序的值
    function fun ({id, name, age}) {
        //id   = "007";
        //name = "Conan";
        //age  = 28;
    };
    fun({id: "007", name: "Conan", age: 28});        

5、提取Json数据

var jsonData = {
        id: "007",
        name: "Conan",
        age: 28,
        score: {
            Chinese: 98,
            Math: 148,
            English: 107
        }
    };
console.log("ES5:");
    console.log("Person's Number is:" + jsonData.id);
    console.log("Person's Name is:" + jsonData.name);
    console.log("Person's age is:" + jsonData.age);
    console.log("Person's Chinese score is:" + jsonData.score.Chinese);
    console.log("Person's Math score is:" + jsonData.score.Math);
    console.log("Person's English score is:" + jsonData.score.English);

console.log("ES6:");
    let { id: number, name, age, score: score } = jsonData;
    console.log("Person's Number is:" + number);
    console.log("Person's Name is:" + name);
    console.log("Person's age is:" + age);
    console.log("Person's Chinese score is:" + score.Chinese);
    console.log("Person's Math score is:" + score.Math);
    console.log("Person's English score is:" + score.English);

6、函数参数的默认值

    jQuery.ajax({
      url: '/path/to/file',
      type: 'POST',
      dataType: 'xml/html/script/json/jsonp',
      data: {param1: 'value1'},
      complete: function(xhr, textStatus) {
        //called when complete
      },
      success: function(data, textStatus, xhr) {
        //called when successful
      },
      error: function(xhr, textStatus, errorThrown) {
        //called when there is an error
      }
    });
    
    jQuery.ajax = function (url, {
        async = true,
        beforeSend = function() {},
        cache = true,
        complete = function() {},
        crossDomain = false,
        global = true,
        // ...more config
    }) {
        // ... do stuff
    };
    //    避免了在函数体内部再写 var foo = config.foo || 'default foo'; 这样的语句

7、遍历Map结构

var map = new Map();
    map.set("id", "007");
    map.set("name", "Conan");

    console.log(map);
    console.log(typeof(map));

    //    获取键名和键值
    for (let [key, value] of map) {
        console.log(key + " is " + value);
    };
    // id is 007
    // name is Conan

    //    获取键名
    for (let [key] of map) {
        console.log(key);
    };
    // id
    // name

    for (let [, value] of map) {
        console.log(value);
    };
    // 007
    // Conan

8、输入模块的指定方法

const { SourceMapConsumer, SourceNode } = require("source-map");