With React 16.8, React Hooks are available in a stable release!
\nHooks let you use state and other React features without writing a class. You can also build your own Hooks to share reusable stateful logic between components.
\nIf you’ve never heard of Hooks before, you might find these resources interesting:
\nYou don’t have to learn Hooks right now. Hooks have no breaking changes, and we have no plans to remove classes from React. The Hooks FAQ describes the gradual adoption strategy.
\nWe don’t recommend rewriting your existing applications to use Hooks overnight. Instead, try using Hooks in some of the new components, and let us know what you think. Code using Hooks will work side by side with existing code using classes.
\nYes! Starting with 16.8.0, React includes a stable implementation of React Hooks for:
\nNote that to enable Hooks, all React packages need to be 16.8.0 or higher. Hooks won’t work if you forget to update, for example, React DOM.
\nReact Native will support Hooks in the 0.59 release.
\nReact Hooks are now supported by React DevTools. They are also supported in the latest Flow and TypeScript definitions for React. We strongly recommend enabling a new lint rule called eslint-plugin-react-hooks to enforce best practices with Hooks. It will soon be included into Create React App by default.
We described our plan for the next months in the recently published React Roadmap.
\nNote that React Hooks don’t cover all use cases for classes yet but they’re very close. Currently, only getSnapshotBeforeUpdate() and componentDidCatch() methods don’t have equivalent Hooks APIs, and these lifecycles are relatively uncommon. If you want, you should be able to use Hooks in most of the new code you’re writing.
Even while Hooks were in alpha, the React community created many interesting examples and recipes using Hooks for animations, forms, subscriptions, integrating with other libraries, and so on. We’re excited about Hooks because they make code reuse easier, helping you write your components in a simpler way and make great user experiences. We can’t wait to see what you’ll create next!
\nWe have added a new API called ReactTestUtils.act() in this release. It ensures that the behavior in your tests matches what happens in the browser more closely. We recommend to wrap any code rendering and triggering updates to your components into act() calls. Testing libraries can also wrap their APIs with it (for example, react-testing-library’s render and fireEvent utilities do this).
For example, the counter example from this page can be tested like this:
\nimport React from 'react';\nimport ReactDOM from 'react-dom';\nimport { act } from 'react-dom/test-utils';import Counter from './Counter';\n\nlet container;\n\nbeforeEach(() => {\n container = document.createElement('div');\n document.body.appendChild(container);\n});\n\nafterEach(() => {\n document.body.removeChild(container);\n container = null;\n});\n\nit('can render and update a counter', () => {\n // Test first render and effect\n act(() => { ReactDOM.render(<Counter />, container); }); const button = container.querySelector('button');\n const label = container.querySelector('p');\n expect(label.textContent).toBe('You clicked 0 times');\n expect(document.title).toBe('You clicked 0 times');\n\n // Test second render and effect\n act(() => { button.dispatchEvent(new MouseEvent('click', {bubbles: true})); }); expect(label.textContent).toBe('You clicked 1 times');\n expect(document.title).toBe('You clicked 1 times');\n});The calls to act() will also flush the effects inside of them.
If you need to test a custom Hook, you can do so by creating a component in your test, and using your Hook from it. Then you can test the component you wrote.
\nTo reduce the boilerplate, we recommend using react-testing-library which is designed to encourage writing tests that use your components as the end users do.
We’d like to thank everybody who commented on the Hooks RFC for sharing their feedback. We’ve read all of your comments and made some adjustments to the final API based on them.
\nReact v16.8.0 is available on the npm registry.
\nTo install React 16 with Yarn, run:
\nyarn add react@^16.8.0 react-dom@^16.8.0To install React 16 with npm, run:
\nnpm install --save react@^16.8.0 react-dom@^16.8.0We 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.
\n\n\nNote
\nAs mentioned above, we strongly recommend using the
\neslint-plugin-react-hookslint rule.If you’re using Create React App, instead of manually configuring ESLint you can wait for the next version of
\nreact-scriptswhich will come out shortly and will include this rule.
Assuming you already have ESLint installed, run:
\n# npm\nnpm install eslint-plugin-react-hooks --save-dev\n\n# yarn\nyarn add eslint-plugin-react-hooks --devThen add it to your ESLint configuration:
\n{\n \"plugins\": [\n // ...\n \"react-hooks\"\n ],\n \"rules\": {\n // ...\n \"react-hooks/rules-of-hooks\": \"error\"\n }\n}useReducer Hook lazy initialization API. (@acdlite in #14723)useState and useReducer Hooks. (@acdlite in #14569)useEffect/useMemo/useCallback Hooks. (@acdlite in #14594)Object.is algorithm for comparing useState and useReducer values. (@Jessidhia in #14752)React.lazy(). (@gaearon in #14626)undefined or a function. All other values, including null, are not allowed. @acdlite in #14119shouldComponentUpdate in the presence of getDerivedStateFromProps for Shallow Renderer. (@chenesan in #14613)ReactTestRenderer.act() and ReactTestUtils.act() for batching updates so that tests more closely match real behavior. (@threepointone in #14744)The above changelog contains all notable changes since our last stable release (16.7.0). As with all our minor releases, none of the changes break backwards compatibility.
\nIf you’re currently using Hooks from an alpha build of React, note that this release does contain some small breaking changes to Hooks. We don’t recommend depending on alphas in production code. We publish them so we can make changes in response to community feedback before the API is stable.
\nHere are all breaking changes to Hooks that have been made since the first alpha release:
\nuseMutationEffect. (@sophiebits in #14336)useImperativeMethods to useImperativeHandle. (@threepointone in #14565)useState and useReducer Hooks. (@acdlite in #14569)useEffect/useMemo/useCallback Hooks. (@acdlite in #14594)Object.is algorithm for comparing useState and useReducer values. (@Jessidhia in #14752)useReducer Hook lazy initialization API. (@acdlite in #14723)