Today we’re releasing React 16.6 with a few new convenient features. A form of PureComponent/shouldComponentUpdate for function components, a way to do code splitting using Suspense and an easier way to consume Context from class components.
\nCheck out the full changelog below.
\nReact.memo Class components can bail out from rendering when their input props are the same using PureComponent or shouldComponentUpdate. Now you can do the same with function components by wrapping them in React.memo.
const MyComponent = React.memo(function MyComponent(props) {\n /* only rerenders if props change */\n});React.lazy: Code-Splitting with Suspense You may have seen Dan’s talk about React Suspense at JSConf Iceland. Now you can use the Suspense component to do code-splitting by wrapping a dynamic import in a call to React.lazy().
import React, {lazy, Suspense} from 'react';\nconst OtherComponent = lazy(() => import('./OtherComponent'));\n\nfunction MyComponent() {\n return (\n <Suspense fallback={<div>Loading...</div>}>\n <OtherComponent />\n </Suspense>\n );\n}The Suspense component will also allow library authors to start building data fetching with Suspense support in the future.
\n\n\nNote: This feature is not yet available for server-side rendering. Suspense support will be added in a later release.
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static contextType In React 16.3 we introduced the official Context API as a replacement to the previous Legacy Context API.
\nconst MyContext = React.createContext();We’ve heard feedback that adopting the new render prop API can be difficult in class components. So we’ve added a convenience API to consume a context value from within a class component.
\nclass MyClass extends React.Component {\n static contextType = MyContext;\n componentDidMount() {\n let value = this.context;\n /* perform a side-effect at mount using the value of MyContext */\n }\n componentDidUpdate() {\n let value = this.context;\n /* ... */\n }\n componentWillUnmount() {\n let value = this.context;\n /* ... */\n }\n render() {\n let value = this.context;\n /* render something based on the value of MyContext */\n }\n}static getDerivedStateFromError() React 16 introduced Error Boundaries for handling errors thrown in React renders. We already had the componentDidCatch lifecycle method which gets fired after an error has already happened. It’s great for logging errors to the server. It also lets you show a different UI to the user by calling setState.
Before that is fired, we render null in place of the tree that threw an error. This sometimes breaks parent components that don’t expect their refs to be empty. It also doesn’t work to recover from errors on the server since the Did lifecycle methods don’t fire during server-side rendering.
We’re adding another error method that lets you render the fallback UI before the render completes. See the docs for getDerivedStateFromError().
\n\nNote:
\ngetDerivedStateFromError()is not yet available for server-side rendering. It is designed to work with server-side rendering in a future release. We’re releasing it early so that you can start preparing to use it.
In 16.3 we introduced the StrictMode component. It lets you opt-in to early warnings for patterns that might cause problems in the future.
We’ve added two more APIs to the list of deprecated APIs in StrictMode. If you don’t use StrictMode you don’t have to worry; these warning won’t fire for you.
contextType API makes this a bit easier.If you’re having trouble upgrading, we’d like to hear your feedback.
\nReact v16.6.0 is available on the npm registry.
\nTo install React 16 with Yarn, run:
\nyarn add react@^16.6.0 react-dom@^16.6.0To install React 16 with npm, run:
\nnpm install --save react@^16.6.0 react-dom@^16.6.0We also provide UMD builds of React via a CDN:
\n<script crossorigin src=\"https://unpkg.com/react@16/umd/react.production.min.js\"></script>\n<script crossorigin src=\"https://unpkg.com/react-dom@16/umd/react-dom.production.min.js\"></script>Refer to the documentation for detailed installation instructions.
\nReact.memo() as an alternative to PureComponent for functions. (@acdlite in #13748)React.lazy() for code splitting components. (@acdlite in #13885)React.StrictMode now warns about legacy context API. (@bvaughn in #13760)React.StrictMode now warns about findDOMNode. (@sebmarkbage in #13841)unstable_AsyncMode to unstable_ConcurrentMode. (@trueadm in #13732)unstable_Placeholder to Suspense, and delayMs to maxDuration. (@gaearon in #13799 and @sebmarkbage in #13922)contextType as a more ergonomic way to subscribe to context from a class. (@bvaughn in #13728)getDerivedStateFromError lifecycle method for catching errors in a future asynchronous server-side renderer. (@bvaughn in #13746)<Context> is used instead of <Context.Consumer>. (@trueadm in #13829)window.event in development. (@sergei-startsev in #13697)React.memo(). (@alexmckenley in #13855)contextType. (@alexmckenley and @sebmarkbage in #13889)scheduler. (@gaearon in #13683)requestAnimationFrame earlier. (@acdlite in #13785)envify transform to the package. (@mridgway in #13766)