2015年值得关注的几个WEB技术

￡神魔★判官ぃ 2022-08-07 02:50 228阅读 0赞

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     <span style="word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">HTTP2</span></span> 
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     <span style="font-size:14px; word-wrap:break-word">&nbsp; &nbsp; &nbsp; HTTP2在今年中应该就可以定稿，这无疑是web界的一个大事。HTTP2从google的SPDY中借鉴了很多特性，重点改善了之前HTTP协议在当前的网络环境下的性能。简单地来讲，HTTP2更快。为什么呢，有几个主要改变：</span> 
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     <span style="font-size:14px; word-wrap:break-word"><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp; &nbsp; &nbsp;</span><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp;</span>首先是来自于同一个domain的HTTP请求可以共享同一个TCP连接了，这样可以很大程度上解决网络延时带来的性能问题。比如你有很多图片，现在也不用sprite化了，因为反正它们会用同一个连接的。HTTP2的出现让之前的很多web前端优化技术可能不再需要了。</span> 
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     <span style="font-size:14px; word-wrap:break-word"><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp; &nbsp; &nbsp;</span><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp;</span>HTTP2不再是纯文本的了，而是二进制的协议了，这样协议的解析也更简单，而传输也更快。缺点是debug的时候需要费点功夫了。</span> 
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     <span style="font-size:14px; word-wrap:break-word"><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp; &nbsp; &nbsp;</span><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp;</span>HTTP2还有其他一些特性，例如header压缩等，大家可以到这里集中<a href="http://daniel.haxx.se/http2/" style="word-wrap:break-word; color:rgb(51,51,51); text-decoration:none" rel="nofollow"><span style="color:#0000f0; word-wrap:break-word">学习一下</span></a>。或者看看这个<a href="http://http2.github.io/faq/" style="word-wrap:break-word; color:rgb(51,51,51); text-decoration:none" rel="nofollow"><span style="color:#0000f0; word-wrap:break-word">FAQ</span></a>。</span> 
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     <span style="font-size:14px; word-wrap:break-word"><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp; &nbsp; &nbsp;</span><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp;</span>Firefox已经开始<a href="http://bitsup.blogspot.kr/2015/02/http2-is-live-in-firefox.html" style="word-wrap:break-word; color:rgb(51,51,51); text-decoration:none" rel="nofollow"><span style="color:#0000f0; word-wrap:break-word">支持HTTP2</span></a>，不少浏览器包括chrome之前就支持SPDY，估计对HTTP2的支持也会迅速开始，而nginx目前已经支持SPDY，就看什么时候各大主流web服务器开始支持HTTP2了。</span> 
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     <span style="font-size:14px; word-wrap:break-word"><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp; &nbsp; &nbsp;</span><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp;</span>一个不太好的现状就是开发人员可能得面临HTTP2和HTTP 1.1的同时存在。如果享受HTTP2的好处，同时又能向后兼容HTTP1.1，可能是今后开发人员必须长期面临的问题了。</span> 
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     <span style="word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp; &nbsp; &nbsp;</span><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp;</span>ECMAScript6</span></span> 
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     <span style="font-size:14px; word-wrap:break-word"><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp; &nbsp; &nbsp;</span><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp;</span>我们现在用的javascript（注意，是javascript语言本身，不包含DOM等其他东西）背后的标准是ECMA-262，也叫 ECMAScript 5。它的下一个版本ECMAScript 6（简称es6），已经基本上快定稿了。这个版本里加入了很多开发过程中需要的一些功能，例如：</span> 
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      <li style="word-wrap:break-word; margin:0px; padding:0px; list-style:disc"><span style="word-wrap:break-word; line-height:1.8em"><span style="font-size:14px; word-wrap:break-word">类定义语法，包括super，继承</span></span></li> 
      <li style="word-wrap:break-word; margin:0px; padding:0px; list-style:disc"><span style="word-wrap:break-word; line-height:1.8em"><span style="font-size:14px; word-wrap:break-word">lambda风格的函数定义，=&gt; block level函数定义内的lexical scope的this，默认参数，rest参数等</span></span></li> 
      <li style="word-wrap:break-word; margin:0px; padding:0px; list-style:disc"><span style="word-wrap:break-word; line-height:1.8em"><span style="font-size:14px; word-wrap:break-word">destructuring, 类似于ruby里的 [a, b, c] = [1, 2, 3]，同时也适用于map和set，以及函数参数</span></span></li> 
      <li style="word-wrap:break-word; margin:0px; padding:0px; list-style:disc"><span style="word-wrap:break-word; line-height:1.8em"><span style="font-size:14px; word-wrap:break-word">symbol</span></span></li> 
      <li style="word-wrap:break-word; margin:0px; padding:0px; list-style:disc"><span style="word-wrap:break-word; line-height:1.8em"><span style="font-size:14px; word-wrap:break-word">iterator迭代器和generator，以及新的for of循环语法</span></span></li> 
      <li style="word-wrap:break-word; margin:0px; padding:0px; list-style:disc"><span style="word-wrap:break-word; line-height:1.8em"><span style="font-size:14px; word-wrap:break-word">template string，从此可以像在ruby和shell里一样使用多行字符串</span></span></li> 
      <li style="word-wrap:break-word; margin:0px; padding:0px; list-style:disc"><span style="word-wrap:break-word; line-height:1.8em"><span style="font-size:14px; word-wrap:break-word">module语法，从语言层面上支持了模块</span></span></li> 
      <li style="word-wrap:break-word; margin:0px; padding:0px; list-style:disc"><span style="word-wrap:break-word; line-height:1.8em"><span style="font-size:14px; word-wrap:break-word">另外还有一系列新东西例如promise，proxy，unicode支持等</span></span></li> 
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     <span style="font-size:14px; word-wrap:break-word"><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp; &nbsp; &nbsp;</span><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp;</span>目前chrome和firefox已经开始<a href="http://kangax.github.io/compat-table/es6/" style="word-wrap:break-word; color:rgb(51,51,51); text-decoration:none" rel="nofollow"><span style="color:#0000f0; word-wrap:break-word">逐步支持es6</span></a>。不过你不用等到所有浏览器都开始支持es6后才可以使用它，因为目前已经有很多把es6代码编译成es5代码的工具，例如<a href="https://babeljs.io/" style="word-wrap:break-word; color:rgb(51,51,51); text-decoration:none" rel="nofollow"><span style="color:#0000f0; word-wrap:break-word">babel</span></a>和<a href="https://github.com/google/traceur-compiler" style="word-wrap:break-word; color:rgb(51,51,51); text-decoration:none" rel="nofollow"><span style="color:#0000f0; word-wrap:break-word">traceur</span></a>等。有很多<a href="https://github.com/sindresorhus/esnext-showcase" style="word-wrap:break-word; color:rgb(51,51,51); text-decoration:none" rel="nofollow"><span style="color:#0000f0; word-wrap:break-word">js的库</span></a>已经开始使用es6的各种功能了，其中包括angular 2.0。</span> 
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     <span style="font-size:14px; word-wrap:break-word"><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp; &nbsp; &nbsp;</span><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp;</span>很多人应该在用coffeescript，es6的很多功能弥补了之前es5的缺陷，吸收了很多coffeescript的功能，也许以后我们就可 以不用coffeescript了，除非你不喜欢大括号小括号，而喜欢python的语法。不过如果coffeescript不进行升级，估计就享受不到 将来es6带来的好处，也难以适应<a href="http://www.html5cn.org/" style="word-wrap:break-word; color:rgb(68,68,68)!important; text-decoration:none!important; border-bottom-width:1px; border-bottom-style:solid; border-bottom-color:blue" rel="nofollow">HTML5</a>时代各种数值计算的需求。</span> 
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     <span style="font-size:14px; word-wrap:break-word"><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp; &nbsp; &nbsp;</span><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp;</span>最后给大家一个比较不错的<a href="https://leanpub.com/understandinges6/read%5D" style="word-wrap:break-word; color:rgb(51,51,51); text-decoration:none" rel="nofollow"><span style="color:#0000f0; word-wrap:break-word">es6学习资源</span></a>，这本书写得很细，现在还是在线免费的。</span> 
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     <span style="font-size:14px; word-wrap:break-word"><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp;<span style="word-wrap:break-word">&nbsp;&nbsp; &nbsp;</span></span><span style="word-wrap:break-word"><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp;</span>Immutable js and React</span></span> 
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     <span style="font-size:14px; word-wrap:break-word"><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp; &nbsp; &nbsp;</span><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp;</span>React相信大家已经不陌生了，它是facebook开源的一个前端view框架，这里之所以提到它是因为它背后的理念所带动的一些技术。 React本身虽然只是一个view框架，但是背后的virtual dom以及随之带来的性能优势是吸引人的地方，另外就是它采用的类似web component的封装概念。这里有一个比较js前端框架性能的<a href="http://evancz.github.io/todomvc-perf-comparison/" style="word-wrap:break-word; color:rgb(51,51,51); text-decoration:none" rel="nofollow"><span style="color:#0000f0; word-wrap:break-word">试验</span></a>，虽然不是很准确，但是可以作一个参考。</span> 
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     <span style="font-size:14px; word-wrap:break-word"><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp; &nbsp; &nbsp;</span><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp;</span>React的virtual dom以及它管理前端控件数据的方法，和immutable数据结构（<a href="https://github.com/facebook/immutable-js" style="word-wrap:break-word; color:rgb(51,51,51); text-decoration:none" rel="nofollow"><span style="color:#0000f0; word-wrap:break-word">immuatble js</span></a>，&nbsp;<a href="https://github.com/elierotenberg/remutable" style="word-wrap:break-word; color:rgb(51,51,51); text-decoration:none" rel="nofollow"><span style="color:#0000f0; word-wrap:break-word">remutable</span></a>）、functional programming是可以很容易结合起来使用的。clojurescript的<a href="https://github.com/omcljs/om" style="word-wrap:break-word; color:rgb(51,51,51); text-decoration:none" rel="nofollow"><span style="color:#0000f0; word-wrap:break-word">om</span></a>框架就是一个例子。想象一下所有的状态都是不可变的，并且统一数据存储（flux架构例如<a href="http://martyjs.org/" style="word-wrap:break-word; color:rgb(51,51,51); text-decoration:none" rel="nofollow"><span style="color:#0000f0; word-wrap:break-word">marty</span></a>），每次数据的更新都可以很容易只<a href="https://blog.rotenberg.io/flux-over-the-wire-3/" style="word-wrap:break-word; color:rgb(51,51,51); text-decoration:none" rel="nofollow"><span style="color:#0000f0; word-wrap:break-word">传递diff</span></a>（event source模式），整个数据在前端的流动都是单向的，不仅变成模型变得简单，而且因为所有的历史数据都没有被实际修改过，所以undo和redo的实现也会变得很容易。</span> 
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     <span style="font-size:14px; word-wrap:break-word"><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp; &nbsp; &nbsp;</span><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp;</span>React通过virtual dom实现了immediate模式的UI编程，低成本和快速的UI刷新也带了人们更多启发，并且React这种封装方式也变得不局限于dom view了。例如flipboard团队基于React的封装风格在canvas上封装了一层<a href="http://engineering.flipboard.com/2015/02/mobile-web/" style="word-wrap:break-word; color:rgb(51,51,51); text-decoration:none" rel="nofollow"><span style="color:#0000f0; word-wrap:break-word">UI</span></a>，可以实现精细的动画效果，保证web版和移动版的体验一致。facebook的React团队最近在React会议上也发布了一个可以用js和React API进行原生移动开发的<a href="http://jlongster.com/First-Impressions-using-React-Native" style="word-wrap:break-word; color:rgb(51,51,51); text-decoration:none" rel="nofollow"><span style="color:#0000f0; word-wrap:break-word">框架</span></a>。</span> 
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     <span style="font-size:14px; word-wrap:break-word"><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp; &nbsp; &nbsp;</span><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp;</span>React也许只是另外一个web view框架，但是我喜欢它给我带来的一些新想法，这些想法也许可以让我们在前端开发上更容易些。</span> 
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     <span style="font-size:14px; word-wrap:break-word"><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp;<span style="word-wrap:break-word">&nbsp;&nbsp; &nbsp;</span></span><span style="word-wrap:break-word"><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp;</span>Realtime web（实时web技术）</span></span> 
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     <span style="font-size:14px; word-wrap:break-word"><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp; &nbsp; &nbsp;</span><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp;</span>现在的web对实时性要求越来越高，这不光是由于现在的技术可以更好地支持实时性，也是由于用户体验的驱动。实时性不光是体现在聊天这种需求上；我们在手机上的操作，web浏览器上最好能够实时体现出来，即便我们不刷新页面，页面也应该能够实时得到更新。</span> 
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     <span style="font-size:14px; word-wrap:break-word"><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp; &nbsp; &nbsp;</span><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp;</span>前端由于HTML5的出现对于实时需求有了更好的技术支持，例如新的WebSocket、WebRTC，long polling以及server push技术。而后端则早就出现了async IO编程技术，能够同时支持大量长连接。但是这些技术的进步从来没有停止过，这里给大家随便介绍几个。</span> 
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     <span style="font-size:14px; word-wrap:break-word"><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp; &nbsp; &nbsp;</span><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp;</span><a href="http://pushpin.org/" style="word-wrap:break-word; color:rgb(51,51,51); text-decoration:none" rel="nofollow"><span style="color:#0000f0; word-wrap:break-word">pushpin</span></a>是fanout最近开源的 一个高性能实时web后端技术，不同于其它的技术，它是一个proxy，本身不提供API编程框架，而是和已有的web API结合起来，让它们变成支持大量长连接的API。从设计概念上，它把维护大量长连接这个功能和实际的API业务功能分离开来，让前一个功能通过 proxy的形式来实现，因此对实际API的框架和语言没有要求，如果要支持更多长连接，也可以通过横向扩展这个proxy来实现，而不一定要改动后端 API。</span> 
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     <span style="font-size:14px; word-wrap:break-word"><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp; &nbsp; &nbsp;</span><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp;</span><a href="http://sockjs.org/" style="word-wrap:break-word; color:rgb(51,51,51); text-decoration:none" rel="nofollow"><span style="color:#0000f0; word-wrap:break-word">sockjs</span></a>，是一个websocket的模拟，在支持websocket的浏览器上就会使用原生websocket，而在老的浏览器上则提供替代技术。但是它不止是一个前端js库，它也同时提供了后端的编程框架，目前支持的语言和框架挺多了。</span> 
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     <span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span> 
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    <div style="word-wrap:break-word"> 
     <span style="font-size:14px; word-wrap:break-word"><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp; &nbsp; &nbsp;</span><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp;</span><a href="http://websocketd.com/" style="word-wrap:break-word; color:rgb(51,51,51); text-decoration:none" rel="nofollow"><span style="color:#0000f0; word-wrap:break-word">websocketd</span></a>是一个有意思的东西，它可以把任何符合接口的程序编程一个websocket后端，你甚至可以用shell来写API。</span> 
    </div> 
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     <span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span> 
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     <span style="font-size:14px; word-wrap:break-word"><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp; &nbsp; &nbsp;</span><span style="word-wrap:break-word; line-height:25.2000007629395px">&nbsp;</span>很多的web框架都支持异步编程模式，因而可以支持大量并发长连接。也有类似于meteor这种提供整体解决方案的，还有很多近期的firebase，大家有兴趣可以自己去找找看。</span> 
    </div> </td> 
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