为什么使用React

一、
1、React
是Facrbook和Instagram用来创建用户界面的JavaScript库。很多人认为React是MVC中的V（视图）；React其实为了解决一个问题，就是构建随着时间数据不断变化的大规模应用程序。
2、简单
仅仅只要表达出你的应用程序在任何时间是什么样子，当底层的数据变化了，React会自动处理所有用户界面的更新。
3、声名式（Declarative）
数据变化后，React概念上与点击“刷新”按钮类似，但仅当会更新变化的部分。
4、构建可组合的组件
React都是关于构建可复用的组件，事实上，通过React你唯一要做的就是构建组件。组件使代码复用、测试和关注分离（separation of concerns）更加简单。

官方博客内容：

Why did we build React?

June 5, 2013 by Pete Hunt

There are a lot of JavaScript MVC frameworks out there. Why did we build React and why would you want to use it?

React isn't an MVC framework.

React is a library for building composable user interfaces. It encourages the creation of reusable UI components which present data that changes over time.

React doesn't use templates.

Traditionally, web application UIs are built using templates or HTML directives. These templates dictate the full set of abstractions that you are allowed to use to build your UI.

React approaches building user interfaces differently by breaking them into components. This means React uses a real, full featured programming language to render views, which we see as an advantage over templates for a
few reasons:

JavaScript is a flexible, powerful programming language with the ability to build abstractions. This is incredibly important in large applications.

By unifying your markup with its corresponding view logic, React can actually make views easier to extend and maintain.

By baking an understanding of markup and content into JavaScript, there's no manual string concatenation and
therefore less surface area for XSS vulnerabilities.

We've also created JSX, an optional syntax extension, in case you prefer the readability of HTML to raw JavaScript.

Reactive updates are dead simple.

React really shines when your data changes over time.

In a traditional JavaScript application, you need to look at what data changed and imperatively make changes to the DOM to keep it up-to-date. Even AngularJS, which provides a declarative interface via directives and data binding requires
a linking function to manually update DOM nodes.

React takes a different approach.
When your component is first initialized, the render method
is called, generating a lightweight representation of your view. From that representation, a string of markup is produced, and injected into the document. When your data changes, the render method
is called again. In order to perform updates as efficiently as possible, we diff the return value from the previous call to render with the new one, and
generate a minimal set of changes to be applied to the DOM.
The data returned from render is
neither a string nor a DOM node -- it's a lightweight description of what the DOM should look like.

We call this process reconciliation. Check out this jsFiddle to
see an example of reconciliation in action.

Because this re-render is so fast (around 1ms for TodoMVC), the developer doesn't need to explicitly specify data bindings. We've found this approach makes it easier to build apps.

HTML is just the beginning.

Because React has its own lightweight representation of the document, we can do some pretty cool things with it:

Facebook has dynamic charts that render to <canvas> instead of HTML.

Instagram is a "single page" web app built entirely with React and Backbone.Router. Designers
regularly contribute React code with JSX.

We've built internal prototypes that run React apps in a web worker and use React to drive native iOS views via
an Objective-C bridge.

You can run React on the server for
SEO, performance, code sharing and overall flexibility.

Events behave in a consistent, standards-compliant way in all browsers (including IE8) and automatically use event
delegation.

Head on over to facebook.github.io/react to check out what we have built. Our documentation is geared towards building apps with the
framework, but if you are interested in the nuts and bolts get in touch with us!

Thanks for reading!