ES6-阮一峰

&lt;script src="traceur.js"&gt;</script&gt;
<script src="bootstrap.js"&gt;</script&gt;
<script type="module"&gt;
  //code  这里写你的jsx代码
</script>

const a = 'Tab';
alert(a);   
// 1.不能重复定义
// 2.常量不能修改

var str1 = `我是${name}，今年${age}岁，性别${sex}的了，爱好${hobby}`; //注意此处有两个“ `` ”
var str2 = '我是'+name+'，今年'+age+'岁，性别'+sex+'，爱好'+hobby+''; //这个是原来的写法

'use strict';
let a = 12;
let b = 5;
let c = 8;

let [a,b,c] = [12,5,8];
console.log(a,b,c);  //12 5 8

let {a,b,c} = {a:12,b:5,c:8};
let [a,[b,c],d] = [12,[1,3],8];

let {a,b,c} = {b:5,a:12,c:8};
console.log(a,b,c);   //12  5  8

let json = {
  q:"aaa",
  p:false,
  s:["aaa"]
};
let {s,q} = json;
console.log(s,q);  //s为数组的数据，q为字符串aaa

let {time=1000,id=0} = {};
console.log(time,id);   //  1000   0

var arr = [12,5,8];
arr2 = arr;
arr2.pop();
alert(arr);  // 12 5

var arr = [12,5,8];
var arr2 =[];
for(var i = 0;i < arr.length; i++){
  arr2.push(arr[i]);    
}
arr2.pop();
alert(arr);   //  12  5  8

var arr = [12,5,8];
var arr2 = Array.from(arr);
arr2.pop();
console.log(arr2);  // 12  5 
console.log(arr);   // 12  5  8

Array.from({length:3}, () => {
  console.log('0');
});

var arr = [12,5,8];
var arr2 = [...arr];

function show(...arr){
  arr.push(8);
  console.log(arr);
}
show(12,5);  //12 5 8

let map = new Map();
map.set('a','apple');
map.set('b','banana');
console.log(map); 
//Map {"a" => "apple", "b" => "banana"}

console.log(map.get('b'));  
map.delete("a");

console.log(map.size); //1
console.log(map.length); //undefined

let map = new Map();
map.set('a','apple');
map.set('b','banana');
console.log(map.entries());  //  MapIterator {["a", "apple"], ["b", "banana"]}

// MDN说明: Map.prototype.entries() 这个方法返回一个新的迭代器对象，对于每一个元素包含键值对(在这个map对象中按照插入的顺序输出)
// The entries() method returns a new Iterator(迭代器) object that contains the [key, value] pairs for each element in the Map object in insertion order.
//关于迭代器(Iterator)和生成器(generator) 在ES6中新引入，单独学习。

// 迭代器中的元素不能直接读取，可以通过下面两种方法进行读取。
// 方法一：
let arr = [];
let map = new Map();
for(let [key, val] of map.entries()) {
    arr.push([key, val]);
}
// 方法二：
var map = new Map();
Array.from(map);

let map = new Map();
map.set('a','apple');
map.set('b','banana');
for(let name of map){
  console.log(name);  //["a", "apple"]  ["b", "banana"]
}
//循环出来的是以数组套键值对的方式

let map = new Map();
map.set('a','apple');
map.set('b','banana');
for(let val of map.values()){
  console.log(val);   //apple   banana
}

let map = new Map();
map.set('a','apple');
map.set('b','banana');
for(let key of map.keys()){
  console.log(key);  // a  b
}

let map = new Map();
map.set('a','apple');
map.set('b','banana');
for(let [key,value] of map.entries()){
  console.log(key,value);   //a apple     b banana
}

//循环数组
let arr = [12,5,8];
for(let i = 0;i<arr.length;i++) {
  console.log(i);    //0 1  2
  console.log(arr[i]);  //12  5  8
} 
let arr = [12,5,8];
for(let i in arr) {
  console.log(i);      //0 1  2
  console.log(arr[i]);  //12  5  8
}

//循环json数据
let json = {a:12,b:5,c:8};
for(let name in json){
  console.log(name);  //a  b c
  console.log(json[name]);  //12 5 8
}

//循环数组
let arr = [12,5,8];
for(let name of arr){
  console.log(name);  // 12 5 8
}
//循环json数据
let json = {a:'apple',b:'banana'};
for(let name of json){
  console.log(name); //error
}
//报错，因为不能用for ...of...来循环json数据

let json = {a:12,b:5};
delete json.a;
console.log(json);  // b:5

var show = function(){
  alert(12);
};
show();   // 12

const show = (num1, num2) =>{
  alert(num1 + num2);
};
show(1, 11);  // 12 

//ES5函数写法
var sum = function(a,b){
  return a+b;
}
alert(sum(12,5));
//ES6函数写法
let sum = (a,b) => {
  return a+b;
}
alert(sum(12,5));
//进化一下  ---   省略花括号
let sum = (a,b) => a+b;
alert(sum(12,5));

var show = function(a){ return 'welcome'}
//相当于   省略括号
var show = a => 'welcome'

var show = function(){ return 'welcome'}
//相当于   省略括号
var show = () => 'welcome'

var show = (a,b) => console.log(this.arguments);     // 报错

var arr = [12,55,8];
//es5写法
arr.sort(function(n1,n2){
  return n1 - n2;
});
//es6写法
arr.sort((n1,n2) => n1-n2);
alert(arr);

let name = 'Datura';
let age = 18;
let person = {
  name,
  age,
  sex:'Man',
  showName:function(){return this.name},
  showAge:function(){return this.age}    
};
alert(person.showAge());    //18
alert(person.sex);    //Man

function Person(name,age){
  this.name = name;
  this.age = age;
}
Person.prototype.showName = function() {
  return this.name;    
};
Person.prototype.showAge = function() {
  return this.age;    
};
var p1 = new Person('alice',18);
alert(p1.showAge());   //18

//定义一个Person构造函数
function Person(name,age){
  this.name = name;
  this.age = age;
}
Person.prototype.showName = function(){
  return this.name;    
};
Person.prototype.showAge = function(){
  return this.age;    
};

//Worker构造函数
//继承属性 
function Worker(name,age,job) {
  //改变this指向，继承Person的属性
  Person.apply(this,arguments);
  //定义worker新的属性
  this.job = job;
}

//继承方法
Worker.prototype = new Person();
//给worker指定“亲爹”
Worker.prototype.construcotr = Worker;
//定义worker新的方法
Person.prototype.showJob = function(){
  return this.job;
};

//调用
var p2 = new Worker('Datura',20,'boss');
alert(p2.showName());   //Datura
alert(p2.showJob());      //boss

class Person{
  constructor(name, age=25){  //可以给属性初始值或默认值,正常es的function函数也可以给默认值
    this.name = name;
    this.age = age;
  }
  showName(){
    return this.name;    
  }
  showAge(){
    return this.age;
  }    
}
var p1 = new Person('alice',18);
alert(p1.showAge());   // 18

//父类构造函数Person
class Person{
  constructor(name,age){
    this.name = name;
    this.age = age;
  }
  showName(){
    return this.name;   
  }
  showAge(){
    return this.age;
  }    
}

//子类继承父类
class Worker extends Person {
  constructor(name,age,job='搬砖的'){   //继承父类属性，并新加属性给默认值
    super(name,age);    
    //这里必须传参，也就是需要把原来构造函数的参数传入。
    //子类必须在constructor方法中调用super方法，否则新建实例时会报错。
    //这是因为子类没有自己的this对象，而是继承父类的this对象，然后对其进行加工。如果不调用super方法，子类就得不到this对象。
    this.job = job;
  }
  //给子类定义新方法showJob
  showJob(){
    return this.job;
  }    
}
//调用
var w1 = new Worker('rose',17);
alert(w1.showJob());
alert(w1.showName());

a).导出，将变量a“暴露”出去
const a =12;
export default a;

b).导入1.js文件“暴露”的东西，并用modA 接收
import modA from './1.js'; (./代表同级目录下)

c).同一个模块导出多个值 export default {a:12,b:5};

d).不同模块间的引入
import modA from './mod1.js';
import modB from './mod2.js';
let sum = modA+modB;
export default sum;

//mod1.js文件的内容
const a = 12;
export default a;

//mod2.js文件的内容
const b = 5;
export default c;

//主入口(模块)的内容<script src="traceur.js"></script>
<script src="bootstrap.js"></script>
<script type="module">
    import modA from './mod1.js';
    import modB from './mod2.js';
    alert(modA+modB);   //17
</script>

//mod3.js文件的内容
export default {a:12,b:5};
//主入口(模块)的内容
import modA from './mod3.js';
console.log(modA.a+modA.b);   //  17

// CommonJS模块
let { stat, exists, readFile } = require('fs');

// 等同于
let _fs = require('fs');
let stat = _fs.stat;
let exists = _fs.exists;
let readfile = _fs.readfile;

import { stat, exists, readFile } from 'fs';

// profile.js
export var firstName = 'Michael';
export var lastName = 'Jackson';
export var year = 1958;

// profile.js
var firstName = 'Michael';
var lastName = 'Jackson';
var year = 1958;

export {firstName, lastName, year};

export function multiply(x, y) {
  return x * y;
};

function v1() { ... }
function v2() { ... }

export {
  v1 as streamV1,
  v2 as streamV2,
  v2 as streamLatestVersion
};

// 写法一
export var m = 1;

// 写法二
var m = 1;
export {m};

// 写法三
var n = 1;
export {n as m};


// 报错
export 1;

// 报错
var m = 1;
export m;

// 报错
function f() {}
export f;

// 正确
export function f() {};

// 正确
function f() {}
export {f};

function foo() {
  export default 'bar' // SyntaxError
}
foo()

// main.js
import {firstName, lastName, year} from './profile';

function setName(element) {
  element.textContent = firstName + ' ' + lastName;
}

import { lastName as surname } from './profile';

// circle.js。输出两个函数
export function area(radius) {
  return Math.PI * radius * radius;
}
export function circumference(radius) {
  return 2 * Math.PI * radius;
}


// main.js 加载在个模块
import { area, circumference } from './circle';
console.log('圆面积：' + area(4));
console.log('圆周长：' + circumference(14));

//上面写法是逐一指定要加载的方法，整体加载的写法如下。
import * as circle from './circle';
console.log('圆面积：' + circle.area(4));
console.log('圆周长：' + circle.circumference(14));

import * as circle from './circle';

// 下面两行都是不允许的
circle.foo = 'hello';
circle.area = function () {};

// export-default.js
export default function () {
  console.log('foo');
}

// import-default.js
import customName from './export-default';
customName(); // 'foo'

// 第一组
export default function crc32() { // 输出
  // ...
}

import crc32 from 'crc32'; // 输入

// 第二组
export function crc32() { // 输出
  // ...
};

import {crc32} from 'crc32'; // 输入

import(specifier)

const main = document.querySelector('main');
import(`./section-modules/${someVariable}.js`).then(module => {
  module.loadPageInto(main);
}).catch(err => {
  main.textContent = err.message;
});

button.addEventListener('click', event => {
  import('./dialogBox.js').then(dialogBox => {
    dialogBox.open();
  }).catch(error => {
    /* Error handling */
  })
});

if (condition) {
  import('moduleA').then(...);
} else {
  import('moduleB').then(...);
}