【翻译】ExtJS vs AngularJS

ExtJS和AngularJS是两个行业内领先的富界面开发框架。TechFerry有机会使用Ext JS和Angular JS来开发多个富界面的单页面应用程序。本文讲述的就是使用这两种技术来开发多个应用程序后的开发体验。本文围绕利弊、架构、测试、移动能力、性能、生成和部署等方面对Ext JS和Angular JS进行了超过30个以上的要点进行了比较。

我们将通过使用Ext JS和Angular JS开发一个测试应用程序来了解架构细节，以便进行详细的性能比较测试。对于性能报告，我们使用了类似的组件集，采用了固定的生成过程，以确保比较是同类比较。

Sencha Ext JS

业界最强大的富界面应用程序开发框架
无与伦比的跨浏览器兼容性
先进的MVC架构
无插件的图表
现代UI部件

AngularJS

HTML增强的Web应用程序

与其他库的完整扩展能力和好的协同表现

开源的Javascript框架，由谷歌维护

声明式编程

Sencha ExtJS 和AngularJS 的比较

Sno	功能	ExtJS	AngularJS
1.	一站式富界面应用程序	✔	✘
2.	具有丰富的主题套件能力的UI组件	✔	幸运的是，有大量的开源的商业组件，为Angular JS提供了集成组件，包括AngularUI、AngularUI Bootstrap、Kendo（或Angular-Kend）、Wijmo或其他。
3.	打页面应用程序的设计	✔	✔
4.	跨浏览器兼容性	✔	Angular JS依赖于jqLite/JQuery来提供跨浏览器的兼容能力。但与其他第三方库集成可能需要跨浏览器兼容能力。注意：Angular JS（1.3及以上）已经不支持IE8了，而Sencha Ext JS 5还会继续支持IE8。如果你的企业用户需要支持IE8，应考虑Ext JS。
5.	图表	Ext JS独立图表是业内最强大和最先进的，对于大多数商业应用程序来说，它的插件是免费和足够应付的。	AngularJS D3图表基本上就是集成的D3图表，这让它拥有了令人惊异的图表和图形绘制功能。使用D3.js，你会爱上D3图表的。
6.	学习曲线	高	中等
架构
7.	应用程序设计框架	MVC 还可看看 ExtJS 5 Beta	MVW (Model-View-Whatever). 它可支持流行的模式，如模型-视图-控制器或模型-视图-视图模型
8.	依赖注入	对于依赖注入，Ext JS可以通过扩充Deft JS来添加Ioc（Inversion of Control，控制反转）容器。	✔
9.	双向数据绑定	✔	✔
10.	直接的DOM操作	✔	✔
11.	模块化	✔	✔
测试
12.	自动化测试支持	可通过外部工具实现	✔
13.	测试框架或测试运行器	一些流行的第三放javascript测试框架，如Siesta（专门为Ext JS进行了优化）、Jasmine和Mocha，都可用于测试。	AngularJS依靠它自己的端到端测试运行器（Karma）来实现集成测试。Protractor就是针对Angular应用程序的端到端测试框架。
性能
14.	Dom 算法	深度优先、自底往上的算法	对于DOM树，指令是深度优先、自底往上的算法。而对于控制器则是自上往下的方式。
15.	性能	较高的覆盖面/重量，因此Ext JS相对比较慢。	在性能测试中，Angular比Ext JS轻3倍。请参阅性能比较统计。
16.	轻量级-较小的下载覆盖面	✘	✔
移动能力
17.	Web应用程序的移动支持	Sencha建议使用Sencha Touch来开发应用程序的移动版本。在移动设备上，像嵌套列表这样的组件比网格更实用。不过，这意味着需要为应用程序开发移动版本。	使用ng-touch库实现响应式Web应用程序，angular-gestures（手势）和AngularJS响应式模块。
18.	跨平台本地移动应用程序/混合应用程序	通过Sencha Touch集成Apache Cordova/Phonegap实现。	通过Trigger.io、Cordova/Phonegap集成基于AngularJS优化过Ionic框架实现，可用来开发富界面和可靠的移动应用程序。
19.	移动网站	Sencha touch可用来开发移动网站。	AngularJS响应模块（angular-responsive, angular-deckgrid等）、UI Boostrap、AngularJS responsive directives, angular-gestures 和ngTouch库。
路由
20.	内置路由	✘ 参阅 ExtJS 5 Beta	✔
21.	深度链接	✘ 参阅 ExtJS 5 Beta	✔
22.	浏览器历史、向前、向后按钮支持t	通过Ext.util.History实现	✔
23.	浏览器书签支持	✘ 参阅ExtJS 5 Beta	✔
24.	SEO支持	大多数单页面应用程序需要通过身份验证后才能使用，因而一般不需要SEO索引。对于公共页面，可使用静态HTML/CSS来实现，如果需要实现的动态内容，可考虑AjaxBased SEO。	可考虑使用Prerender.io或在Web服务器中实现无头的浏览器支持来实现基于Ajax的SEO。
部署
25.	生成工具	针对Ext JS 4.x+的Sencha cmd 工具或针对Ext JS 3.x的Sencha sdk工具	第三放的 Grunt 工具
26.	包管理工具	Sencha cmd	Yeoman, Grunt 或 Bower
协议和支持
27.	协议：开源或商业	Per-seat / per-server的商业协议或GPL许可下的开源协议	MT许可下的开源javascript框架
28.	完整的文档套件、教程、视频示例、培训	✔	✔
29.	支持：一般性讨论、Bug报告和定制功能需求	基于Web的公共或白金（仅付费的订阅用户）支持	公共支持
30.	完全的乐趣和满足：在整个应用程序开发生命周期内，不需要考虑所选择的第三库新版本发布或bug修复	✔	✘
其他
31.	内置动画支持	✔	✔
32.	Deferred 和Promises.	DeftJS提供了一些Ext JS扩展，包含了Deferred和Promises.	✔
33.	Dirty Checking（脏检查）	✔	✔
34.	Deferred Bootstrap	Until now, ExtJS applications' testing has never required delay in the Bootstrap as third-party JavaScript testing frameworks which are used for ExtJS application testing do not require deferring the bootstrap.	Angular Scenario Runner and Batrang require Deferred Bootstrap and hence Deferred Bootstrap concept is introduced to allow end to end tests.

性能比较统计

为了评估这两个框架的性能，我们开发了一个包含网格、树和图表组件的小型的应用程序。这两种技术都是按照规定的生成过程来进行的，因此，我们可以使用最小化的生成来进行量级比较。YSlow用来收集性能数据。其他的细节：

Ext JS：使用网格、树和图表组件

Angular JS：使用angular-charts.min.js、angular.min.js、jquery.min.js、angular-route.min.js、ng-grid-2.0.7.min.js、angular.treeview.min.js、angular-animate.js模块

对于这些组件的数据部分，使用的是同意的http请求，同样的Web服务器。

结论：Ext JS比AngularJS重3倍

Ext JS

AngularJS：

如果使用ext-all，那么统计结果是：

框架的选择：

使用Ext JS：

使用Sencha Ext JS提供的方便的组件，可节省大量时间。

如果担心编程和开发时的兼容性问题，它是一大亮点。

你或你的客户需要专门的许可或专业支持。

如果富桌面应用程序（使用Ext JS）和移动Web应用程序（使用Sencha Touch）是独立，这相当实用。

可承担支持合约或per-seat / per-server 的商业许可。

使用AngularJS：

要求较小的足迹。更多详细信息，请参阅性能比较统计。

应用程序要求响应式设计。

你的组织需要寻求自动化测试的价值，以及自动化测试是你们开发文化的一部分。

要整合的第三放组件是免费的，因而成本比较低。

团队更关注CSS和跨浏览器的兼容性问题。

在整个应用程序开发生命周期内，团队能够很好的管理所集成的第三方库的新版本或bug修复。

架构差异：

我们尝试从以下10个方面来比较Ext JS和AngularJS之间的架构差异：

应用程序设计框架
组件
路由的好处
可测试性
数据绑定
SEO的友好性
移动解决方案
DOM算法
Deferred和Promises
脏检查
Deferred bootstrap

摘要：

Ext JS是基于组件（网格、树、表单和图表）的，代码开始于扩展的API类和配置模块，如果需要，可自定义延时文稿或行为/事件，将这些组件添加到容器/布局。它遵循面向对象原则和MVC模式，很少需要与DOM直接交互。

AngularJS，刚好相反，它是声明式编程，开始时，需要在纯HTML中添加AngularJS指令、配置模块、使用模板或路由来配置视图，而且框架还有关注DOM的创建。由于要处理HTML，因而需要直接与HTML结构或DOM元素交互。


应用程序设计框架
Ext JS: 遵循 MVC框架. 随着Ext JS应用程序的大小和复杂性的增加，Sencha Touch和Ext JS可以通过加入Deft JS来添加Ioc容器、针对依赖注入和动态应用程序的程序集。基于组件和hence模块	AngularJS: AngularJS是增强的HTML Web一个月程序它被描述为“Model-View-Whatever”框架，它没有规定是哪一种特定的应用程序架构或哪一套模式。然而，它足够灵活去支撑流行的模式，如模型-视图-控制器或模型-视图-视图模型。基于模块。依赖于模块内的html元素。
组件:
Ext JS: Ext JS区别于其他框架的一个主要特性就是包含一套有丰富的主题能力的UI组件。 Pros: 使用Ext JS提供的方便的组件可以节省大量时间。 Cons: Sencha组件往往会产生冗长的DOM输出，其结果就是需要更多标签。	AngularJS: AngularJS不能解决的问题是没有丰富用户接口组件。不过，有大量的开源或商业组件可以集成到AngularJS，包括AngularUI、AngularUI Bootstrap、Kendo (或 Angular-Kendo)、 Wijmo以及其他。
路由的好处
ExtJS: Ext JS没有路由。不过，许多单页面应用程序可能不需要路由，除非你希望通过内部/深度链接来实现SEO友好性或支持书签。	AngularJS: AngularJS路由连接着浏览器中的控制器、视图模板和当前URL定位。使用该特性就可实现深度链接。深度链接是由网站中指定的、可搜索的或可索引的内容块的连接所组出的超链接。它可以让我们利用浏览器的历史记录（后退或前进导航）已经浏览器的书签功能。
可测试性:
ExtJS: 使用Sencha框架生成的应用程序可使用几个流行的第三方javascript测试框架来测试，如Siesta（基于Ext JS进行了优化）、Jasmine和Mocha。 Sencha产品套件没有包含测试框架或测试运行器。	AngularJS: AngularJS从创建之初开始就被设计为可测试的应用程序。它支持三方面的自动化测试：单一、集成和功能测试。 AngularJS团队还开发了它自己的Karma测试运行器。另外，第三方工具Protractor是针对Angular应用程序的端到端测试框架。
双向数据绑定: 双向数据绑定是应用程序UI和模型对象之间的粘合剂，这样，对象属性的改变就会反映到UI，反之亦然。
ExtJS: 通过使用存储对象，Ext JS有着优秀的数据绑定功能。为了执行双向数据绑定，还需要执行一些工作，如重新加载存储等等。	AngularJS: AngularJS的双向数据绑定基本上是通过嵌套在原型继承树上的模型来实现的。 Cons: 如果模板绑定的数据有2000到3000，应用程序会变得迟钝。 Bindonce is a great way to minimize the number of watches when most of the data presented in your page, once rendered, are immutable and you need not keep watching them for changes.
SEO Friendliness: Most of the single page apps which work behind authentication need not be indexed for SEO. If you have some pages in your app which are public and which needs to be indexed, you can createthem separately, either with static HTML/CSS or if you do need to use dynamic content, consider Ajaxbased SEO as described below. Ajax based SEO: For the indexing of dynamic / ajax-based single page web apps, all you have to do is to generate the additional static content so that when the crawlers access your page, they get easy access to that static content and when the users access your page, they see the app. To achieve this functionality you could either use some tools like Prerender.io: fully open-source or you have to set up the headless browser support in your web-server which is an additional effort.
ExtJS: Ajax based seo is possible in ExtJS with hashbang urls' support in your web-server.	AngularJS: AngularJS seo with Prerender.io: When a crawler visits your page at hashbang url, the Prerender service will check and see if it has a snapshot or already rendered page for that URL, if yes, it will send it to the crawler, if not, it will render a snapshot on the fly and send the rendered HTML to the crawler for correct indexing. Alternatively, you can also build support for hashbang URLswhich may require you to set-up your web-server to summon-up the headless html browser.
Mobile Solutions:
ExtJS: Sencha Touch - the industry-leading and high-performance mobile HTML5 framework, is used to develop powerful, universal mobile web apps / mobile website. Sencha touch integration with Cordova/Phonegap is used to develop the cross platform hybrid applications.	AngularJS: AngularJS can be used to develop responsive web apps / websites although all the angular modules are not responsive. To develop the cross platform hybrid applications, integrate AngularJS with Trigger.io Ionic Framework - Advanced Html5 hybrid mobile framework and optimized for AngularJS Cordova/Phonegap
Dom Approach:
ExtJS: It follows the Depth First, Bottom-Up approach.	AngularJS: Directives are linked in a Depth-First, Bottom-Up approach to the DOM tree.Controllers are linked in a top-down manner.
Deferred and Promises: Deferred and Promises break the complexities of asynchronous programming, separate out the synchronous and asynchronous world, remove the tight coupling between the twoThey are for asynchronous programming what try, catch and throw keywords are for synchronous programming.
ExtJS: ExtJS augmented with DeftJS may provide Deferred and Promises.	AngularJS: AngularJS offers an implementation of the Q API for Deferred and Promises.
Dirty Checking Dirty checking in nutshell: The framework compares the old value and new value and if they are different, fires the change event.
ExtJS: ExtJS 4.x uses the store's binding feature to execute the dirty checking. ExtJS store allows you to delay the process of dirty checking via its autoSync config which when set to false, the user changes are marked with dirty flags in UI and are updated in batch when the user saves the store. To reflect the changes in the real data in UI, a little work is to be done like reloading the store etc	AngularJS: Angular uses the Digest Cycle to execute the dirty checking. With Angular api, you do not need to manaually call the digest cycle, angular internally fires digest cycle followed by updation of the dom but from third party api, you need to call $apply method to enter the digest cycle. Changes are reflected in the real data in UI as soon as the digest cycle is finished. The dirty checking is done asynchronously. Cons: Application becomes laggy if there are 2000-3000 watches in a template... more Bindonce is a great way to minimize the number of watches when most of the data presented in your page, once rendered, are immutable and you need not keep watching them for changes.
Deferred bootstrap: Bootstrap means the initialization process. Deferred bootstrap is to make a delay in the bootstrap process to mock out the heavy dependencies or for the instrumentation purposes. Deferred bootstrap is primarily introduced to allow end to end tests. Although deferred bootstrap has no value in the developement and testing of most single page applications, yet it serves its value in AngularJS applications' end to end testing. Some javascript test runners such as Batrang and Angular Scenario Runner (which are developed by AngularJS team for the end to end testing of the angularJS applications) require deferred bootstrap.
ExtJS: Several popular third-party JavaScript testing frameworks such as Siesta (optimized specifically for Ext JS), Jasmine and Mocha, are being used for ExtJS applications testing which do not require deferring the ExtJS application's bootstrap.	AngularJS: Batrang is a new Chrome extension, recommended by the angular team, provides the tools to address performance bottlenecks, visualize and debug applications. AngularJS Batarang and Angular Scenario Runner require Deferred Bootstrap feature to hook into angular's bootstrap process and sneak in more modules into the DI registry which can replace or augment DI services for the purpose of instrumentation or mocking out heavy dependencies.
Digest Cycle in AngularJS: The digest cycle is all about reacting to changes in data. Generally what happens is, the browser's event-loop waits for an event to arrive, as long as it recives an event, it emits the event on the input controls which is then captured in the corresponding directive's event handler which calls apply function, to enter into Angular execution context, with function/expression (the work you wish to do in Angular execution context) as parameter. Model mutation is then executed in apply function with all the error handling followed by the firing of the digest cycle in its finally phase. In all the Dirty Cycle mechanisms, all the watchers in the watch list are iterated and in each iteration watch expression in current scope is evaluated, old and new value of scope is compared and if both values differ,then the corresponding listener of the watcher function is fired which upon execution calls digest cycle again with one of the two possilities: If the listener function does not modify the scope then in the running digest turn, model is declared as stable and digest loop is finished followed by the browser re-painting of the DOM node which was dirty. If scope is modified, then it will fire the other listeners, so the watchers keep re-running until until no more watchers are fired and a max limit of 10 iterations is reached when $digest will throw 'Maximum iteration limit exceeded' to prevent infinite loops. This dirty checking is done asynchronously. Three mechanisms of Dirty Checking: Reference-Based Dirty-Checking: The old value is compared to the new with the strict equality operator=== which detect the new and old values are the same "physical" object.It is the most efficient both in terms of computation and memory, since it doesn't do copying or traversal. It merely keeps a reference to the value around for comparison. Value-Based Dirty-Checking: It performs a deep-object-tree comparison.This means that within each $digest cycle, AngularJS will check to see if the new and old values have the same structure. Collection-based dirty checking: It works by comparing physical object references. Collection watchers keep an internal copy of the array or object, and traverse the old and new values in each digest cycle, checking for changes using the strict equality operator === i.e. unlike the reference based dirty checking, it goes one-level deep and performs an additional, shallow reference check of the top level items in the collection. Cons of dirty checking: Application becomes laggy if there are 2000-3000 watches in a template. Although anything faster than 50ms is imperceptible to humans and you can't really show more than about 2000 pieces of information to a human on a single page because anything more than that is really a bad UI and humans can't process this anyway, yet while building any sort of widget or data grid with two-way binding you may easily hit 2000 bindings without the bad UI. Watcher: By default all the model data that is bound to UI are being watched upon i.e. they all have a watcher registered in the watch list, a collection used by digest cycle for the dirty checking. You can also attach a watcher to the scope by using $watch function. A watcher has two functions: A watch function or a watch expression, which specifies the piece of data you are interested in. A listener function which will be called whenever that data changes. Asynchronous nature of dirty cycle: Assignment such as $scope.username="angular" will not immediately cause a $watch to be notified, instead the $watch notification is delayed until the $digest phase. This delay is desirable, since it coalesces multiple model updates into one $watch notification as well as it guarantees that during the $watch notification no other $watches are running. If a $watch changes the value of the model, it will force additional $digest cycle.
ExtJS 5 Beta: Recently launched ExtJS5 Beta version provides support for router and hence deep linking is now possible.ExtJS 5 also supports MVC and MVVM. We will review and update the article as and when new and stable versions of ExtJS and AngularJS are released.