<KeepAlive> is a component that maintains component state and avoids repeated re-rendering.

• Only based on React Fiber and React Hooks.
• Triggers original class component life circle.
• Triggers original effect hooks.
• Supports context updates.
• Supports multiple keep-alive.
• Supports react-dom v16.8+.
• Supports react-dom v17.
• Supports react-dom v18.

npm install --save react-fiber-keep-alive

import React from 'react';
import ReactDOM from 'react-dom';
import KeepAlive from 'react-fiber-keep-alive';

const root = document.getElementById('root');

ReactDOM.render((
    <KeepAlive.Provider value={root}>
        ...
        <KeepAlive name="test">
            <YourComponent />
        </KeepAlive>
        ...
    </KeepAlive.Provider>
), root);

• Provide root container element.

  <KeepAlive.Provider value={container}>

  • Must be the root container of render().
  • If not provided, keep-alive will be disabled.

• Wrap your component with <KeepAlive>

  <KeepAlive name="unique-key">
      <YourComponent />
  </KeepAlive>

  • prop "name" is a required unique string used to identify the cache.
  • prop "ignore" is a optional boolean used to bypass and clear the cache. (since 0.5.0)
  • prop "onRead(name: string): void" is a optional callback after cache applied. (since 0.7.0)
  • prop "onSave(name: string): void" is a optional callback after cache saved. (since 0.7.0)

• Wrap your component with keepLive().

  import { keepAlive } from 'react-fiber-keep-alive';
  
  const NewComponent = keepAlive(YourComponent, (props) => {
      // props: the income props for `<YourComponent>`
      
      // you can use react hooks here
  
      return `unique-key`;
  
      // or
  
      return {
          name: `unique-key`,
          // other props for `<KeepAlive>`
      };
  });

• Hook: useIgnoreKeepAlive() returns a cache cleaner function.

  import { useIgnoreKeepAlive } from 'react-fiber-keep-alive';
  
  const ignoreCache = useIgnoreKeepAlive();
  
  ignoreCache(`unique-key`);

• If the render() of class component has side effects.

  import { markClassComponentHasSideEffectRender } from 'react-fiber-keep-alive';
  
  markClassComponentHasSideEffectRender(ClassComponent);
  
  // Example:
  class Test extends React.Component {
      render() {
          // side effect here, ex: emit event here.
          return null;
      }
  }
  markClassComponentHasSideEffectRender(Test);

• If no need to trigger the effect hook while remounting.

  import { markEffectHookIsOnetime } from 'react-fiber-keep-alive';
  
  markEffectHookIsOnetime(effectHook);
  
  // Example:
  React.useEffect(markEffectHookIsOnetime(() => {
      // do something
  }), []);
  React.useLayoutEffect(markEffectHookIsOnetime(() => {
      // do something
  }), []);

• KeepAlive.Context (since 0.7.0)

  import * as React from 'react';
  import KeepAlive, { Context, KeepAliveCache } from 'react-fiber-keep-alive';
  import LRUCache from 'lru-cache';
  
  /// Example: Use LRU to manage the cache
  const YourKeepAliveProvider: React.FC<{
      children: React.ReactNode;
      value: null | HTMLElement;
  }> = (props) => {
      const container = props.value;
      const context: Context = React.useMemo(() => {
          if (!container) {
              return [];
          }
          const caches = new LRUCache<string, KeepAliveCache>({ 
              max: 10,
          });
          return [container, caches, new Map()];
      }, []);
  
      return (
          <KeepAlive.Context.Provider value={context}>
              {props.children}
          </KeepAlive.Context.Provider>
      );
  };

• Be careful the global side effects. (ex: insert global style)
• Do not use <KeepAlive> under the <React.StrictMode>.
• Recursive <KeepAlive> handled by top level <KeepAlive>.
• If the container changed in ReactDOM.createPortal(children, container).
  • All saved sub tree state will be lost.
• Errors from react-devtools after <KeepAlive> remounted.
  • Try force refresh the components tree. (ex: updates components filter)

• react-router v5

• render(children, container)
• hydrate(children, container)

• createRoot(container).render(children)
• hydrateRoot(container, children)

• Component.getDerivedStateFromProps()
• Component.getDerivedStateFromError()
• instance.componentDidMount()
• instance.getSnapshotBeforeUpdate()
• instance.componentDidUpdate()
• instance.componentWillUnmount()
• instance.render()

• useContext()
• useCallback()
• useEffect()
• useImperativeHandle()
• useLayoutEffect()
• useMemo()
• useRef()
• useState()
• useDebugValue()
• useDeferredValue() (since v18)
• useId() (since v18)
• useInsertionEffect() (since v18)
• useSyncExternalStore() (since v18)
• useTransition() (since v18)

• ReactDOM.createPortal(children, container)
• React.memo()
• React.forwardRef()
• React.lazy()
• <Suspense>
• <Offscreen> (since v18)

If you find a bug, please file an issue on our issue tracker on GitHub.

Copyright © 2022 Shen Junru • MIT license.