30-seconds-of-code/snippets/useRequestAnimationFrame.md

title, tags, firstSeen

title	tags	firstSeen
useRequestAnimationFrame	hooks,effect,intermediate	2021-12-29T05:00:00-04:00

Runs an animating function, calling it before every repaint.

• Use the useRef() hook to create two variables. requestRef will hold the last request id and previousTimeRef will hold the last timestamp.
• Define a function, animate, which handles updating these variables, runs the callback and calls Window.requestAnimationFrame() perpetually.
• Use the useEffect() hook with an empty array to initialize the value of requestRef using Window.requestAnimationFrame(). Use the returned value and Window.cancelAnimationFrame() to clean up when the component unmounts.

const useRequestAnimationFrame = callback => {
  const requestRef = React.useRef();
  const previousTimeRef = React.useRef();

  const animate = time => {
    if (previousTimeRef.current) callback(time - previousTimeRef.current);
    previousTimeRef.current = time;
    requestRef.current = requestAnimationFrame(animate);
  };

  React.useEffect(() => {
    requestRef.current = requestAnimationFrame(animate);
    return () => cancelAnimationFrame(requestRef.current);
  }, []);
};

const Counter = () => {
  const [count, setCount] = React.useState(0);

  useRequestAnimationFrame(deltaTime => {
    setCount(prevCount => (prevCount + deltaTime * 0.01) % 100);
  });

  return <p>{Math.round(count)}</p>;
};

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