React useTimeout hook

React, Hooks, Effect · Nov 16, 2020

Implements setTimeout() in a declarative manner.

  • Create a custom hook that takes a callback and a delay.
  • Use the useRef() hook to create a ref for the callback function.
  • Use the useEffect() hook to remember the latest callback.
  • Use the useEffect() hook to set up the timeout and clean up.
const useTimeout = (callback, delay) => {
  const savedCallback = React.useRef();

  React.useEffect(() => {
    savedCallback.current = callback;
  }, [callback]);

  React.useEffect(() => {
    const tick = () => {
      savedCallback.current();
    }
    if (delay !== null) {
      let id = setTimeout(tick, delay);
      return () => clearTimeout(id);
    }
  }, [delay]);
};
const OneSecondTimer = props => {
  const [seconds, setSeconds] = React.useState(0);
  useTimeout(() => {
    setSeconds(seconds + 1);
  }, 1000);

  return <p>{seconds}</p>;
};

ReactDOM.render(<OneSecondTimer />, document.getElementById('root'));

Written by Angelos Chalaris

I'm Angelos Chalaris, a JavaScript software engineer, based in Athens, Greece. The best snippets from my coding adventures are published here to help others learn to code.

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