React 16.3.0 发布，构建用户界面的 JavaScript 库

React 16.3.0 已发布，React 是 Facebook 推出的一个为数据提供渲染为 HTML 视图，用来构建用户界面的开源 JavaScript 库。

React 视图通常采用包含以自定义 HTML 标记规定的其他组件的组件渲染。React 为程序员提供了一种子组件不能直接影响外层组件（"data flows down"）的模型，数据改变时对 HTML 文档的有效更新，和现代单页应用中组件之间干净的分离。

更新内容：

React

• Add a new officially supported context API
• Add a new React.createRef() API as an ergonomic alternative to callback refs.
• Add a new React.forwardRef() API to let components forward their refs to a child. 
• Fix a false positive warning in IE11 when using React.Fragment
• Replace React.unstable_AsyncComponent with React.unstable_AsyncMode
• Improve the error message when calling setState() on an unmounted component.

React DOM

• Add a new getDerivedStateFromProps() lifecycle and UNSAFE_ aliases for the legacy lifecycles. 
• Add a new getSnapshotBeforeUpdate() lifecycle
• Add a new <React.StrictMode> wrapper to help prepare apps for async rendering. 
• Add support for onLoad and onError events on the <link> tag
• Add support for noModule boolean attribute on the <script> tag
• Fix minor DOM input bugs in IE and Safari
• Correctly detect Ctrl + Enter in onKeyPress in more browsers
• Fix containing elements getting focused on SSR markup mismatch
• Fix value and defaultValue to ignore Symbol values
• Fix refs to class components not getting cleaned up when the attribute is removed. 
• Throw with a meaningful message if the component runs after jsdom has been destroyed. 
• Don't crash if there is a global variable called opera with a null value
• Don't check for old versions of Opera
• Deduplicate warning messages about <option selected>
• Deduplicate warning messages about invalid callback
• Deprecate ReactDOM.unstable_createPortal() in favor of ReactDOM.createPortal(). 
• Don't emit User Timing entries for context types
• Improve the error message when context consumer child isn't a function. 
• Improve the error message when adding a ref to a functional component. 

React DOM Server

• Prevent an infinite loop when attempting to render portals with SSR.
• Warn if a class doesn't extend React.Component. 
• Fix an issue with this.state of different components getting mixed up.
• Provide a better message when component type is undefined.

React Test Renderer

• Fix handling of fragments in toTree(). 
• Shallow renderer should assign state to null for components that don't set it. 
• Shallow renderer should filter legacy context according to contextTypes. 
• Add an unstable API for testing asynchronous rendering.

React Is (New)

• First release of the new package that libraries can use to detect different React node types. 
• Add ReactIs.isValidElementType() to help higher-order components validate their inputs. 

React Lifecycles Compat (New)

• First release of the new package to help library developers target multiple versions of React. 

Create Subscription (New)

• First release of the new package to subscribe to external data sources safely for async rendering. 

React Reconciler (Experimental)

• Expose react-reconciler/persistent for building renderers that use persistent data structures. 
• Pass host context to finalizeInitialChildren().
• Remove useSyncScheduling from the host config.

React Call Return (Experimental)

• Fix a crash on updates.

下载地址：https://github.com/facebook/react/releases/tag/v16.3.0