ES6 clean up

1. Variable declaration let and const

Both let and const are block-scoped.

• let

function name(){
    let age = 12; //age只在name()函数中存在
}

• const

const name = 'tom'
name = 'jack'//再次赋值会报错

2. String Template

• Es5

//例1
var name = 'jack';
console.log('hello '+name)
//例2
var msg = 'Hi \
man!
'//以反斜杠用来换行

• Es6

//例1
const name = 'jack'
console.log('hello ${name}');//hello jack
//例2
onst template = `<div>
        <span>hello world</span>
    </div>`

3. Extending the functionality of the object

• Es5

//例1
function people(name,age){
    return {
        name:name
        age:age
    }
}
//例2
const people = {
    name : 'tom',
    getThisName:function(){
        console.log(this.name)
    }
}

• Es6

//例1
function people(name,age){
    return {
        name
        age
    }
}
//例2
const people = {
    name : 'tom',
    getThisName(){
        console.log(this.name)
    }
}

4.import and export

//全部导入
import people from './example'

//有一种特殊情况，即允许你将整个模块当作单一对象进行导入
//该模块的所有导出都会作为对象的属性存在
import * as example from "./example.js"
console.log(example.name)
console.log(example.age)
console.log(example.getName())

//导入部分
import {name, age} from './example'

// 导出默认, 有且只有一个默认
export default App

// 部分导出
export class App extend Component {};

5.Class support

Support for class classes was added in Es6:

//定义class
class Animal(){
    //ES6中新型构造器
    constructor(name) {
        this.name = name;
    }
    //实例方法
    sayName() {
        console.log('My name is '+this.name);
    }
}

//类的继承
class Programmer extends Animal {
    constructor(name) {
    	//直接调用父类构造器进行初始化
        super(name);
    }
    program() {
        console.log("I'm coding...");
    }
}
//测试我们的类
var animal=new Animal('dummy'),
wayou=new Programmer('wayou');
animal.sayName();//输出 ‘My name is dummy’
wayou.sayName();//输出 ‘My name is wayou’
wayou.program();//输出 ‘I'm coding...’

6.for of

var someArray = [ "a", "b", "c" ];
 
for (v of someArray) {
    console.log(v);//输出 a,b,c
}