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<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>ES6 必知必会</title>
<meta name="apple-mobile-web-app-capable" content="yes">
<meta name="apple-mobile-web-app-status-bar-style" content="black-translucent">
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no, minimal-ui">
<link rel="stylesheet" href="css/reveal.css">
<link rel="stylesheet" href="css/theme/moon.css" id="theme">
<!-- Code syntax highlighting -->
<link rel="stylesheet" href="lib/css/zenburn.css">
<!-- Printing and PDF exports -->
<script>
var link = document.createElement( 'link' );
link.rel = 'stylesheet';
link.type = 'text/css';
link.href = window.location.search.match( /print-pdf/gi ) ? 'css/print/pdf.css' : 'css/print/paper.css';
document.getElementsByTagName( 'head' )[0].appendChild( link );
</script>
<!--[if lt IE 9]>
<script src="lib/js/html5shiv.js"></script>
<![endif]-->
<style type="text/css">
.reveal h1, .reveal h2, .reveal h3, .reveal h4, .reveal h5, .reveal h6 {
text-transform: none;
}
.reveal ol, .reveal dl, .reveal ul {
display: block;
font-size: .7em;
}
.reveal li {
margin: .5em 0;
}
</style>
</head>
<body>
<div class="reveal">
<!-- Any section element inside of this container is displayed as a slide -->
<div class="slides">
<section>
<h1>ES6 必知必会</h1>
<br/>
<br/>
<br/>
<p>by <a href="https://github.com/llh911001">@llh911001</a></p>
<p>2016/1/13</p>
</section>
<section>
<h2>变量和参数</h2>
</section>
<section>
<section>
<h3>let 声明</h3>
<div class="fragment">
<ul>
<li>块级作用域</li>
</ul>
<pre><code class="hljs" data-trim contenteditable>
if(true) {
let a = 1
}
console.log(a)
// a is not defined
</code></pre>
</div>
<div class="fragment">
<ul>
<li>不可重复声明</li>
</ul>
<pre><code class="hljs" data-trim contenteditable>
let a = 1
let a = 2
// Duplicate declaration "a"
</code></pre>
</div>
</section>
<section>
<ul>
<li>以前</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
for (var i=0; i<10; i++) {
setTimeout(~function(a) {
console.log(a)
}(i), 100)
}
// 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
</code></pre>
<div class="fragment">
<ul>
<li>现在</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
for (let i=0; i<10; i++) {
setTimeout(() => {
console.log(i)
}, 100)
}
// 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
</code></pre>
</div>
</section>
</section>
<section>
<h3>const 声明</h3>
<div class="fragment">
<ul>
<li>定义常量</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
const CONSTANT = 'a constant'
CONSTANT = 'something else'
// "CONSTANT" is read-only
// 重新为一个常量赋值会报错
</code></pre>
</div>
<div class="fragment">
<ul>
<li>不可只声明不赋值</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
const CONSTANT
// Syntax error: Unexpected token
</code></pre>
</div>
<div class="fragment">
<ul>
<li>对象常量是可变的</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
const CONSTANT = {foo: 1}
CONSTANT.foo = 2
// 正常运行
</code></pre>
</div>
</section>
<section>
<section>
<h3>默认参数</h3>
<div class="fragment">
<ul>
<li>以前</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
function work(name) {
name = name || 'Bender'
return name
}
work()
// Bender
</code></pre>
</div>
<div class="fragment">
<ul>
<li>现在</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
function work(name = 'Bender') {
return name
}
work()
// Bender
</code></pre>
</div>
</section>
<section>
<ul>
<li>多个参数</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
function work(name = 'Bender', hobby = 'drinking') {
return `${name} likes ${hobby}`
}
work()
// Bender likes drinking
</code></pre>
<div class="fragment">
<ul>
<li>与普通参数混合使用</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
function work(foo, name = 'Bender', hobby = 'drinking', bar) {
return `${name} likes ${hobby}`
}
work()
// Bender likes drinking
</code></pre>
</div>
</section>
</section>
<section>
<section>
<h3>rest 参数</h3>
<pre class="fragment"><code class="javascript hljs" data-trim contenteditable>
function foo(...args) {
console.log(args);
}
foo(1, 2, 3)
// [1, 2, 3]
foo()
// []
</code></pre>
</section>
<section>
<div>
<ul>
<li><code>...args</code> 只能出现在函数参数列表的最后一个位置</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
// 报错
function foo(...args, name) { // Syntax error: Unexpected token
console.log(name)
}
// 正常运行
function bar(name, ...args) {
console.log(name)
}
bar('Bender')
// Bender
</code></pre>
</div>
</section>
<section>
<h3>告别 <code>arguments</code></h3>
</section>
</section>
<section>
<section>
<h3>扩展运算符</h3>
<pre class="fragment"><code class="javascript hljs" data-trim contenteditable>
function foo(a, b, c) {
return a + b + c
}
foo(...[1, 2, 3])
// 6
</code></pre>
</section>
<section>
<div>
<ul>
<li>在一个数组中扩展另一个数组</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
let a = [3, 4, 5]
let b = [1, 2, ...a, 6, 7]
console.log(b)
// [1, 2, 3, 4, 5, 6, 7]
</code></pre>
</div>
<div class="fragment">
<ul>
<li>给函数传的数组元素过多？</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
function foo(a, b, c) {
return a + b + c
}
foo(...[1, 2, 3, 4, 5, 6])
// 6
// 后面的被忽略了
</code></pre>
</div>
</section>
</section>
<section>
<section>
<h3>解构赋值</h3>
<div class="fragment">
<ul>
<li>解构数组</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
let values = [42, 73]
let [a, b] = values
console.log(a, b)
// 42, 73
</code></pre>
</div>
<div class="fragment">
<ul>
<li>解构对象</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
let bender = {name: 'Bender', hobby: 'drinking'}
let {name, hobby} = bender
console.log(name, hobby)
// Bender, drinking
</code></pre>
</div>
</section>
<section>
<div>
<ul>
<li>调换变量值</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
let a = 1, b = 2
[a, b] = [b, a]
console.log(a, b)
// 2, 1
</code></pre>
</div>
<div class="fragment">
<ul>
<li>等式两边的数组元素位置是严格对应的</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
let values = [1, 2, 3]
let [, a, b, c] = values
console.log(a, b, c)
// 2, 3, undefined
</code></pre>
</div>
</section>
</section>
<section>
<section>
<h3>模版字符串</h3>
<pre class="fragment"><code class="javascript hljs" data-trim contenteditable>
let name = 'Bender'
let result = `Hello, ${name}`
console.log(result)
// Hello, Bender
</code></pre>
</section>
<section>
<div>
<ul>
<li>模版字符串中可以有表达式</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
let a = 42, b = 73
let result = `a + b is ${a + b}`
console.log(result)
// a + b is 115
</code></pre>
</div>
<div class="fragment">
<ul>
<li>模版字符串中可以换行</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
let result = `Hello
there, Bender!
`
console.log(result)
// Hello\n there, Bender!
</code></pre>
</div>
</section>
</section>
<section>
<section>
<h3>带标签的模版字符串</h3>
<pre class="fragment"><code class="javascript hljs" data-trim contenteditable>
let name = 'Bender'
let result = test `Hello,${name}!`
function test(literals, ...values) {
console.log(literals) // ['Hello,', '!']
console.log(values) // ['Bender']
return 'test'
}
console.log(result)
// test
</code></pre>
<ul>
<li class="fragment">标签函数与模版字符串之间可以有多个空格，甚至换行符</li>
<li class="fragment">标签函数返回的值是模版字符串的最终结果</li>
</ul>
</section>
</section>
<section>
<h2>类</h2>
</section>
<section>
<section>
<h3>class 关键字</h3>
<pre class="fragment"><code class="javascript hljs" data-trim contenteditable>
class Animal {
// ...
}
let animal = new Animal()
</code></pre>
</section>
<section>
<ul>
<li>constructor 方法</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
class Animal {
constructor(name) {
this._name = name
}
getName() {
return this._name
}
}
let animal = new Animal('kitty')
animal.getName()
// kitty
</code></pre>
</section>
<section>
<ul>
<li>属性</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
class Animal {
constructor(name) {
this._name = name
}
get name() {
return this._name
}
set name(newName) {
this._name = newName
}
}
let animal = new Animal('kitty')
console.log(animal.name)
// kitty
animal.name = 'doge'
console.log(animal.name)
// doge
</code></pre>
</section>
<section>
<ul>
<li>静态方法</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
class Animal {
constructor(name) {
this._name = name
}
static foo() {
return 'I am a static method'
}
}
let animal = new Animal('kitty')
animal.foo()
// animal.foo is not a function
Animal.foo()
// I am a static method
</code></pre>
</section>
</section>
<section>
<section>
<h3>类的继承</h3>
<pre class="fragment"><code class="javascript hljs" data-trim contenteditable>
class Animal {
constructor(name) {
this._name = name
}
get name() {
return this._name
}
set name(newName) {
this._name = newName
}
say() {
return 'I am an animal'
}
}
class Cat extends Animal {
say() {
return 'I am a cat'
}
}
let cat = new Cat('kitty')
cat.name
// kitty
cat.say()
// I am a cat
</code></pre>
</section>
<section>
<ul>
<li>在 constructor 方法中使用 super</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
class Cat extends Animal {
constructor(name, pet) {
super(name)
this._pet = pet
}
get pet() {
return this._pet
}
}
let cat = new Cat('kitty', 'Bender')
console.log(cat.pet)
// Bender
</code></pre>
</section>
<section>
<ul>
<li>在普通方法中使用 super</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
class Cat extends Animal {
// ...
say() {
return super() + '!'
}
}
// 或者
class Cat extends Animal {
// ...
say() {
return super.say() + '!'
}
}
</code></pre>
</section>
</section>
<section>
<section>
<h3>类的本质</h3>
<pre class="fragment"><code class="javascript hljs" data-trim contenteditable>
let cat = new Cat('kitty')
cat instanceOf Cat
// true
cat instanceOf Animal
// true
</code></pre>
</section>
<section>
<h3>语法糖</h3>
</section>
</section>
<section>
<h2>函数式特性</h2>
</section>
<section>
<section>
<h3>箭头函数</h3>
<pre class="fragment"><code class="javascript hljs" data-trim contenteditable>
let add = (a, b) => a + y
</code></pre>
</section>
<section>
<ul>
<li>参数周围的括号</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
let add = (x, y) => x + y // 必需
let square = x => x * x // 不必需
let compute = () => square(add(5, 3)) // 必需
let result = compute()
// 64
</code></pre>
</section>
<section>
<ul>
<li>函数体的大括号</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
// 正常运行
let add = (x, y) => x + y
// 或者
let add = (x, y) => { return x + y }
// 返回一个对象 {a: 1}
// 失败
let test = () => { a: 1 }
// 成功
let test = () => ({ a: 1 })
// 或者
let test = () => {
return {a: 1}
}
</code></pre>
</section>
</section>
<section>
<section>
<h3>箭头函数和 this</h3>
<div class="fragment">
<ul>
<li>以前</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
function A(name) {
this._name = name
}
A.prototype.later = function() {
var self = this
setTimeout(function() {
console.log(self._name)
}, 100)
}
var a = new A('Bender')
a.later()
// Bender
</code></pre>
</div>
</section>
<section>
<ul>
<li>现在</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
class A {
constructor(name) {
this._name = name
}
later() {
setTimeout(() => console.log(this._name), 100)
}
}
let a = new A('Bender')
a.later()
// Bender
</code></pre>
</section>
<section>
<ul>
<li>
<code>call</code> 和 <code>apply</code> 不影响 <code>this</code>
</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
class A {
constructor(name) {
this._name = name
}
}
let a = new A('Bender')
a.foo = function() { console.log(this._name) }
a.bar = () => { console.log(this._name) }
a.foo.call({_name: 'foo'})
// foo
a.bar.call({_name: 'bar'})
// Cannot read property '_name' of undefined
</code></pre>
</section>
<section>
<h3>告别 <code>self</code></h3>
</section>
</section>
<section>
<section>
<h3>Symbol</h3>
<pre class="fragment"><code class="javascript hljs" data-trim contenteditable>
let s1 = Symbol()
s1.toString()
// Symbol()
type of s1
// symbol
let s2 = Symbol('a symbol')
type of s2
// symbol
s2.toString()
// Symbol(a symbol)
</code></pre>
</section>
<section>
<div>
<ul>
<li>无需 new 关键字</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
let s = new Symbol()
// Symbol is not a constructor
</code></pre>
</div>
<div class="fragment">
<ul>
<li>唯一性</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
let s1 = Symbol('a symbol')
let s2 = Symbol('a symbol')
s1 === s2
// false
</code></pre>
</div>
</section>
<section>
<ul>
<li>作为对象的属性</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
let foo = 'foo'
let bar = Symbol()
let obj = {
foo: foo,
[bar]: 'bar' // 注意新语法
}
console.log(obj.foo)
// foo
console.log(obj[bar])
// bar
</code></pre>
</section>
<section>
<ul>
<li>不可枚举</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
let result = []
for(let a in obj) {
result.push(a)
}
console.log(a)
// ['foo']
</code></pre>
<div class="fragment">
<ul>
<li>不出现在 Object.getOwnPropertyNames 中</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
let keys = Object.getOwnPropertyNames(obj)
console.log(keys)
// ['foo']
</code></pre>
</div>
<div class="fragment">
<ul>
<li>可以使用 Object.getOwnPropertySymbols</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
let smbs = Object.getOwnPropertySymbols(obj)
console.log(obj[smbs[0]])
// bar
</code></pre>
</div>
</section>
</section>
<section>
<section>
<h3>iterable</h3>
<div class="fragment">
<ul>
<li>有 <code>[Symbol.iterator]</code> 方法的对象</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
let iterable = {
index: 0,
[Symbol.iterator]() {
return {
next: () => {
if(this.index < 5) {
this.index++
return {done: false, value: this.index-1}
} else {
return {done: true, value: this.index}
}
}
}
}
}
</code></pre>
</div>
<div class="fragment">
<ul>
<li>用于 <code>for of</code> 循环</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
for(let i of iterable) {
console.log(i)
}
// 1, 2, 3, 4
</code></pre>
</div>
</section>
</section>
<section>
<section>
<h3>iterator</h3>
<pre class="fragment"><code class="javascript hljs" data-trim contenteditable>
let iterator = iterable[Symbol.iterator]()
iterator.next()
// {"value": 1, "done": false}
</code></pre>
<ul>
<li class="fragment">iterable 的 <code>[Symbol.iterator]</code> 方法返回的对象</li>
<li class="fragment"><code>next</code> 方法会返回一个对象</li>
<ul class="fragment">
<li><code>value</code> 是值</li>
<li><code>done</code> 表明是否结束迭代</li>
</ul>
</ul>
</section>
</section>
<section>
<section>
<h3>generator</h3>
<div class="fragment">
<pre><code class="javascript hljs" data-trim contenteditable>
let numbers = function* () {
yield 1
yield 2
yield 3
}
let generator = numbers()
generator.next()
// {"value": 1, "done": false}
for(let i of generator) {
console.log(i)
}
// 2, 3
generator.next()
// {"done": true}
</code></pre>
</div>
</section>
<section>
<ul>
<li>代理 yield</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
function* foo() {
yield 2
yield 3
}
function* bar() {
yield 1
foo() // 没有任何效果
yield 4
}
[...bar()]
// [1, 4]
function* bar() {
yield 1
yield* foo()
yield 4
}
[...bar()]
// [1, 2, 3, 4]
</code></pre>
</section>
<section>
<ul>
<li><code>next</code> 传值</li>
</ul>
<pre><code class="javascript hljs" data-trim contenteditable>
function* foo(x) {
var y = 2 * (yield (x + 1));
var z = yield (y / 3);
return (x + y + z);
}
var it = foo(5);
console.log(it.next()); // { "value": 6, "done": false }
console.log(it.next(12)); // { "value": 8, "done": false }
console.log(it.next(13)); // { "value": 42, "done": true }
</code></pre>
</section>
<section>
<h3>告别 callback hell</h3>
</section>
</section>
<section>
<h2>模块</h2>
</section>
<section>
<section>
<h3>export</h3>
<pre class="fragment"><code class="javascript hljs" data-trim contenteditable>
export default foo
export let foo = 'foo'
export {foo, bar}
export {foo as bar}
export {foo as default} // 等价于 export default foo
</code></pre>
</section>
</section>
<section>
<section>
<h3>import</h3>
<pre class="fragment"><code class="javascript hljs" data-trim contenteditable>
import foo from 'foo'
import {foo, bar} from 'baz'
import {foo as bar} from 'baz'
import {default} from 'foo'