Job-ES6 语法

*块级作用域,字符串,函数
*对象扩展,解构
*类,模块化

使用let 完全可以替换var ,使用var ,在{}之外是可以找到的,使用let在{}之外是找不到的.

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模版字符串

name="imooc";course = "React 开发 App"console.log("hello" + name + ",course is" + course)console.log(`hello ${name},course is ${course}`)支持中间换行的写法

ES6中的函数:

参数默认值

箭头函数

展开运算符

var 不会报错


let 会报错


*js 也拥有了块级作用于,{}中间的作用域,使用let定义,外部是获取不到的,let可以完全替换var 定义一个变量

const name = "experience";name = "solidadc";cosole.log(name);const 定义一个常量,不能给一个常量赋值.

let name = "experience";name = "solidadc";console.log(name);let 不是定义一个常量,可以赋值.

/*var 不会报错,但是let会报错*/// {//     let name = "experience"// }// console.log(name);/*const 定义一个常量,不能给一个常量赋值.*/// const name = "experience";// name = "solidadc";// cosole.log(name);/*let 不是定义一个常量,可以赋值.*/// let name = "experience";// name = "solidadc";// console.log(name);/*模版字符串   中间可以任意换行,都不会报错*/// name = "experience";// course = "solidadc";// console.log("hello " + name +" is course "+course);// console.log(`hello ${name} is course ${course}`);//// console.log(`hello////// ${name} is course////  ${course}`);/*箭头函数   简写函数   保持函数的this作用域*/// function hello(name){//     console.log(`Hello ${name} !`)// }// hello("src");//// const hellos = (name)=>{//     console.log(`Hello ${name} !`)// }// hellos("background");//// setTimeout (()=>{//     console.log("xxx")// },3000)/*如果{}里,只有一条return语句的话,{}是可以省略不写的!~~*/// const double =x =>x*2// console.log(double(5))/*默认参数*/// const hello = (name=`girl`) =>{//     console.log(`Hello ${name}`)// }// hello();// hello("boy");/*展开符的使用*/// function hello(name1,name2){//     console.log(name1,name2);// }// arr = ["girl","boy"]// hello.apply(null,arr)//// hello(...arr)/*对象扩展  Object 扩展   把一个对象压成一个数组  */// obj = {name: "experience",course: "fairy"}// console.log(Object.keys(obj))// console.log(Object.values(obj))// console.log(Object.entries(obj))/*对象展开符 的扩展 */// const obj1 = {name:"experience" ,course:"solidadc"}// const obj2 = {type:"IT"         ,name:"fairy"}// console.log({...obj1,...obj2,data:"2017"})/*数组 解构*/// const arr =["hello","fairy"]// let arg1 = arr[0]// let arg2 = arr[1]// let[arg1,arg2] = arr// console.log(arg1,`|`,arg2)/*对象解构 */// const obj = {name:"experience",course:"fairy"}// const {name,course} = obj// console.log(name,`|`,course)/*提供class的语法糖*是 prototype的语法糖*Extends继承* Constructor构造函数*/// class Myapp {//     constructor(){//         this.name = "experience"//     }//     sayHello(){//         console.log(`hello${this.name}!`)//     }// }// const app = new Myapp()// app.sayHello()/*ES6中新出现的数据结构* set元素不可重合* Map* Symbol*//*ES6中自带了模块化机制,告别sea.js require.js* import,import{}* Export,export default* Node现在还不支持,还需要require来加载* *//*未解之谜*/// import * as mod1 from "./module1"// console.log(mod1)/*遍历数组*/// [1,2,3].forEach(function(value,index){//     console.log(value);// });/*映射新数组*/arr = [1,2,3].map(v=>v*2);/*所有元素是否通过测试*/[1,2,3,4].every(v=>v>3);/*是否有元素通过测试*/[1,2,3,4].some(v=>v>3);/*过滤数组*/[1,2,3,4,5].filter(v=>v>3);/*查找符合条件的元素*/arr = [{name:"xiaoxi",age:"13"},{name:"romio",age:"23"}];/*查找索引*/[1,2,3].indexOf(2);/*连接数组*/arr1=[1,2,3];arr2=[4,5,6];[...arr1,...arr2];/*数组去重*/arr = [1,2,3,4,3,2,1];[...new Set(arr)];/*获取对象的key*/Object.keys({name:"experience",age:"43"})/*获取对象里数据的流量*/Object.keys({name:"experience",age:"43"}).length;/*遍历数组*/Object.entries({name:"experience",age:"43"});/*extend 功能*/const obj = {name:"experience",age:"43"};const newObj = {...obj,job:"IT",age:15};console.log(newObj)/*获取列表的头和尾*/const [head,...tail] = [1,2,3];const [last,...initial] = [1,2,3].reverse();