react-code-dataset / v4 /src /hooks /useScrollDirection.js
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const SCROLL_UP = 'up';
const SCROLL_DOWN = 'down';
import { useState, useEffect } from 'react';
const useScrollDirection = ({ initialDirection, thresholdPixels, off } = {}) => {
const [scrollDir, setScrollDir] = useState(initialDirection);
useEffect(() => {
const threshold = thresholdPixels || 0;
let lastScrollY = window.pageYOffset;
let ticking = false;
const updateScrollDir = () => {
const scrollY = window.pageYOffset;
if (Math.abs(scrollY - lastScrollY) < threshold) {
// We haven't exceeded the threshold
ticking = false;
return;
}
setScrollDir(scrollY > lastScrollY ? SCROLL_DOWN : SCROLL_UP);
lastScrollY = scrollY > 0 ? scrollY : 0;
ticking = false;
};
const onScroll = () => {
if (!ticking) {
window.requestAnimationFrame(updateScrollDir);
ticking = true;
}
};
/**
* Bind the scroll handler if `off` is set to false.
* If `off` is set to true reset the scroll direction.
*/
!off ? window.addEventListener('scroll', onScroll) : setScrollDir(initialDirection);
return () => window.removeEventListener('scroll', onScroll);
}, [initialDirection, thresholdPixels, off]);
return scrollDir;
};
export default useScrollDirection;