ES6、ES7、ES8、ES9、ES10、ES11新特性1

ECMA规范最终由TC39敲定。TC39由包括浏览器厂商在内的各方组成，他们开会推动JavaScript提案沿着一条严格的发展道路前进。
从提案到入选ECMA规范主要有以下几个阶段：
* Stage 0: strawman——最初想法的提交。
* Stage 1: proposal（提案）——由TC39至少一名成员倡导的正式提案文件，该文件包括API事例。
* Stage 2: draft（草案）——功能规范的初始版本，该版本包含功能规范的两个实验实现。
* Stage 3: candidate（候选）——提案规范通过审查并从厂商那里收集反馈
* Stage 4: finished（完成）——提案准备加入ECMAScript，但是到浏览器或者Nodejs中可能需要更长的时间。

class People {
  // 构造函数，实例化的时候将会被调用，如果不指定，那么会有一个不带参数的默认构造函数.
  constructor(name, age) {
    this.name = name;
    this.age = age;
  }
  toString() {
    console.log(`name: ${this.name}, age: ${this.age}`)
  }
}
//实例化 People
const people = new People('灿灿', 40)
people.toString();
console.log(people.hasOwnProperty('name'));
console.log(people.hasOwnProperty('toString'));
console.log(people.__proto__.hasOwnProperty('toString'));
class Cancan extends People {
  constructor(action) {
    // 子类必须要在constructor中指定super 函数，否则在新建实例的时候会报错.
    // 如果没有置顶consructor,默认带super函数的constructor将会被添加、
    super('cancan', '50');
    this.action = action;
  }
  toString() {
    console.log(super.toString());
  }
}
const  cancan = new Cancan('catch')
cancan.toString();
// 实例cancan 是 Cancan 和 People 的实例，和Es5完全一致。
console.log(cancan instanceof People); // true
console.log(cancan instanceof Cancan); // true

//test.js
export const name = 'cancan'

//test.js
 var name = 'Rainbow';
 var age = '24';
 export {name, age};

import {myModule} from 'myModule';// main.js
import {name,age} from 'test';// test.js

// 箭头函数的例子
()=>1
v=>v+1
(a,b)=>a+b
()=>{
    alert("foo");
}
e=>{
    if (e == 0){
        return 0;
    }
    return 1000/e;
}

//ES6
function foo(height = 50, color = 'red')
{
    // ...
}
//ES6之前
function foo(height, color)
{
    var height = height || 50;
    var color = color || 'red';
    //...
}

//ES6
var name = `Your name is ${first} ${last}.`
//ES6之前
var name = 'Your name is ' + first + ' ' + last + '.'

var foo = ["one", "two", "three", "four"];
var [one, two, three] = foo;
console.log(one); // "one"
console.log(two); // "two"
console.log(three); // "three"
//如果你要忽略某些值，你可以按照下面的写法获取你想要的值
var [first, , , last] = foo;
console.log(first); // "one"
console.log(last); // "four"
//你也可以这样写
var a, b; //先声明变量
[a, b] = [1, 2];
console.log(a); // 1
console.log(b); // 2

var a, b;
[a=5, b=7] = [1];
console.log(a); // 1
console.log(b); // 7

var a = 1;
var b = 3;
[a, b] = [b, a];
console.log(a); // 3
console.log(b); // 1

const student = {
  name:'Ming',
  age:'18',
  city:'Shanghai'  
};
const {name,age,city} = student;
console.log(name); // "Ming"
console.log(age); // "18"
console.log(city); // "Shanghai"

['4', ...'hello', 6];// ["4", "h", "e", "l", "l", "o", 6]

let objClone = { ...obj };

var arr = [1, 2, 3];var arr2 = [...arr]; // 等同于 arr.slice()
arr2.push(4); 
console.log(arr2)//[1, 2, 3, 4]

function sum(x, y, z) {
  return x + y + z;
}
const numbers = [1, 2, 3];
//不使用延展操作符
console.log(sum.apply(null, numbers));
//使用延展操作符
console.log(sum(...numbers));// 6

const stuendts = ['Jine','Tom'];const persons = ['Tony',... stuendts,'Aaron','Anna'];
conslog.log(persons)// ["Tony", "Jine", "Tom", "Aaron", "Anna"]
//链接多个数组
var arr1 = [0, 1, 2];
var arr2 = [3, 4, 5];
var arr3 = [...arr1, ...arr2];// 将 arr2 中所有元素附加到 arr1 后面并返回
//等同于
var arr4 = arr1.concat(arr2);

var obj1 = { foo: 'bar', x: 42 };var obj2 = { foo: 'baz', y: 13 };
var clonedObj = { ...obj1 };
// 克隆后的对象: { foo: "bar", x: 42 }
var mergedObj = { ...obj1, ...obj2 };
// 合并后的对象: { foo: "baz", x: 42, y: 13 }

// ES6之前const name='Ming',age='18',city='Shanghai';
const student = {
    name:name,
    age:age,
    city:city
};
console.log(student);//{name: "Ming", age: "18", city: "Shanghai"}
//ES6
const name='Ming',age='18',city='Shanghai';
const student = {
    name,
    age,
    city
};
console.log(student);//{name: "Ming", age: "18", city: "Shanghai"}

//ES6之前
setTimeout(function()
{
    console.log('Hello'); // 1秒后输出"Hello"
    setTimeout(function()
{
        console.log('Hi'); // 2秒后输出"Hi"
    }, 1000);
}, 1000);
//ES6
var waitSecond = new Promise(function(resolve, reject)
{
    setTimeout(resolve, 1000);
});
waitSecond
    .then(function()
{
      console.log("Hello"); // 1秒后输出"Hello"
      return waitSecond;
    })
    .then(function()
{
        console.log("Hi"); // 2秒后输出"Hi"
    });

{  let a = 10;
}
console.log(a); //-1 or Error“ReferenceError: a is not defined”