JavaScript、ES5和ES6的介绍和区别
JavaScript由三部分组成:
- ECMAScript(核心)
- DOM(文档对象模型)
- BOM (浏览器对象模型)
ES5(ECMAScript第五个版本)
- strict模式
严格模式,限制一些用法,'use strict';
- Array增加方法
增加了every、some 、forEach、filter 、indexOf、lastIndexOf、isArray、map、reduce、reduceRight方法
PS: 还有其他方法 Function.prototype.bind、String.prototype.trim、Date.now
- Object方法
Object.getPrototypeOf
Object.create
Object.getOwnPropertyNames
Object.defineProperty
Object.getOwnPropertyDescriptor
Object.defineProperties
Object.keys
Object.preventExtensions / Object.isExtensible
Object.seal / Object.isSealed
Object.freeze / Object.isFrozen
ES6(ECMAScript第六个版本)
ECMAScript6在保证向下兼容的前提下,提供大量新特性
1.块级作用域 关键字let, 常量const
2.函数参数 - 默认值、参数打包、 数组展开(Default 、Rest 、Spread)
//Default
function findArtist(name='lu', age='26') {
...
}
//Rest
function f(x, ...y) {
// y is an Array
return x * y.length;
}
f(3, "hello", true) == 6
//Spread
function f(x, y, z) {
return x + y + z;
}
// Pass each elem of array as argument
f(...[1,2,3]) == 6
3.箭头函数 Arrow functions
(1).简化了代码形式,默认return表达式结果。
(2).自动绑定语义this,即定义函数时的this。
4.字符串模板 Template strings
var name = "Bob", time = "today";
`Hello ${name}, how are you ${time}?`
// return "Hello Bob, how are you today?"
5.Class
Class,有constructor、extends、super,但本质上是语法糖(对语言的功能并没有影响,但是更方便程序员使用)。
class Artist {
constructor(name) {
this.name = name;
}
perform() {
return this.name + " performs ";
}
}
class Singer extends Artist {
constructor(name, song) {
super.constructor(name);
this.song = song;
}
perform() {
return super.perform() + "[" + this.song + "]";
}
}
let james = new Singer("Etta James", "At last");
james instanceof Artist; // true
james instanceof Singer; // true
james.perform(); // "Etta James performs [At last]"
6.Modules
ES6的内置模块功能借鉴了CommonJS和AMD各自的优点:
(1).具有CommonJS的精简语法、唯一导出出口(single exports)和循环依赖(cyclic dependencies)的特点。
(2).类似AMD,支持异步加载和可配置的模块加载。
// lib/math.js
export function sum(x, y) {
return x + y;
}
export var pi = 3.141593;
// app.js
import * as math from "lib/math";
alert("2π = " + math.sum(math.pi, math.pi));
// otherApp.js
import {sum, pi} from "lib/math";
alert("2π = " + sum(pi, pi));
- Proxies
使用代理(Proxy)监听对象的操作,然后可以做一些相应事情。
var target = {};
var handler = {
get: function (receiver, name) {
return `Hello, ${name}!`;
}
};
var p = new Proxy(target, handler);
p.world === 'Hello, world!';
可监听的操作: get、set、has、deleteProperty、apply、construct、getOwnPropertyDescriptor、
defineProperty、getPrototypeOf、setPrototypeOf、enumerate、ownKeys、preventExtensions、isExtensible。
8.Promises
Promises是处理异步操作的对象,使用了 Promise 对象之后可以用一种链式调用的方式来组织代码,
让代码更加直观(类似jQuery的deferred 对象)。
function fakeAjax(url) {
return new Promise(function (resolve, reject) {
// setTimeouts are for effect, typically we would handle XHR
if (!url) {
return setTimeout(reject, 1000);
}
return setTimeout(resolve, 1000);
});
}
// no url, promise rejected
fakeAjax().then(function () {
console.log('success');
},function () {
console.log('fail');
});
参考
http://caibaojian.com/toutiao/6864
附:
ES6语法快速上手
https://segmentfault.com/a/1190000005742091
在React/React Native中ES5与ES6的对比不同点
http://blog.csdn.net/changsimeng/article/details/62883952
相关文章
- 从ES6重新认识JavaScript设计模式(三): 建造者模式
- javascript中var that=this
- [Javascript] Filter out Duplicates from Flat JavaScript Array with array.filter / reduce / Set
- [Javascript] Safely Access a Property on a JavaScript Array with Optional Chaining
- [Javascript] Hide Properties from Showing Up in "for ... in" Loops in JavaScript
- [Cypress] install, configure, and script Cypress for JavaScript web applications -- part4
- [Javascript] Multiply Two Arrays over a Function in JavaScript
- [Javascript AST] 2. Introduction: Write a simple ESLint rule
- [HTML5] Focus management using CSS, HTML, and JavaScript
- [Javascript] Filter out Duplicates from Flat JavaScript Array with array.filter / reduce / Set
- [Javascript] Create an Image with JavaScript Using Fetch and URL.createObjectURL
- [Javascript] Multiply Two Arrays over a Function in JavaScript
- [Algorithms] Divide and Recurse Over an Array with Merge Sort in JavaScript
- [Javascript] Understanding the .constructor property on JavaScript Objects
- [Javascript] Delegate JavaScript (ES6) generator iteration control
- [Javascript] Compose multiple functions for new behavior in JavaScript
- [Javascript] Hoisting in JavaScript
- 使用JavaScript ES6的新特性计算Fibonacci(非波拉契数列)
- JavaScript 异步操作里的嵌套回调函数
- JavaScript面试系列:JavaScript设计模式之桥接模式和懒加载
- 使用Javascript递归遍历本地文件夹
- 【 华为OD机试 2023】 统一限载货物数最小值(C++ Java JavaScript Python)
- Java程序猿JavaScript学习笔记(4——关闭/getter/setter)
- web前端Javascript开发学习之JavaScript中的预编译如何进行
- JavaScript 函数和事件