Class 的基本语法

ES5写法

  1. function Point(x,y){
  2.     this.x = x
  3.     this.y = y
  4. }
  5. Point.prototype.toString = function(){
  6.     return `${this.x} + ${this.x}`
  7. }
  9. var p = new Point(1,2)
  10. console.log(p)
  11. console.log(p.toString())

ES6

  1. class Point{
  2.     constructor(x,y){
  3.         this.x = x;
  4.         this.y = y
  5.     }
  6.     toString(){
  7.         return `${this.x} + ${this.x}`
  8.     }
  9. }

constructor 方法
image.png

解构赋值

用途

交换变量的值

  1. let x = 1;
  2. let y = 2;
  4. [x, y] = [y, x];

从函数返回多个值

  1. // 返回一个数组
  3. function example() {
  4.   return [1, 2, 3];
  5. }
  6. let [a, b, c] = example();
  8. // 返回一个对象
  10. function example() {
  11.   return {
  12.     foo: 1,
  13.     bar: 2
  14.   };
  15. }
  16. let { foo, bar } = example();

提取JSON数据

  1. let jsonData = {
  2.   id: 42,
  3.   status: "OK",
  4.   data: [867, 5309]
  5. };
  7. let { id, status, data: number } = jsonData;
  9. console.log(id, status, number);
  10. // 42, "OK", [867, 5309]

函数参数的默认值

  1. jQuery.ajax = function (url, {
  2.   async = true,
  3.   beforeSend = function () {},
  4.   cache = true,
  5.   complete = function () {},
  6.   crossDomain = false,
  7.   global = true,
  8.   // ... more config
  9. } = {}) {
  10.   // ... do stuff
  11. };

指定参数的默认值，就避免了在函数体内部再写var foo = config.foo || 'default foo';这样的语句。

输入模块的指定方法

指定输入哪些方法

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