Add useRequestAnimationFrame

snippets/useRequestAnimationFrame.md

@@ -0,0 +1,43 @@
+---
+title: useRequestAnimationFrame
+tags: hooks,effect,intermediate
+firstSeen: 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 `return` value and `Window.cancelAnimationFrame()` to clean up when the component unmounts.
+
+```jsx
+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);
+  }, []);
+};
+```
+
+```jsx
+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'));
+```