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const SCROLL_UP = 'up'; |
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const SCROLL_DOWN = 'down'; |
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import { useState, useEffect } from 'react'; |
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const useScrollDirection = ({ initialDirection, thresholdPixels, off } = {}) => { |
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const [scrollDir, setScrollDir] = useState(initialDirection); |
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useEffect(() => { |
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const threshold = thresholdPixels || 0; |
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let lastScrollY = window.pageYOffset; |
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let ticking = false; |
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const updateScrollDir = () => { |
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const scrollY = window.pageYOffset; |
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if (Math.abs(scrollY - lastScrollY) < threshold) { |
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ticking = false; |
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return; |
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} |
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setScrollDir(scrollY > lastScrollY ? SCROLL_DOWN : SCROLL_UP); |
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lastScrollY = scrollY > 0 ? scrollY : 0; |
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ticking = false; |
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}; |
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const onScroll = () => { |
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if (!ticking) { |
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window.requestAnimationFrame(updateScrollDir); |
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ticking = true; |
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} |
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}; |
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!off ? window.addEventListener('scroll', onScroll) : setScrollDir(initialDirection); |
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return () => window.removeEventListener('scroll', onScroll); |
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}, [initialDirection, thresholdPixels, off]); |
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return scrollDir; |
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}; |
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export default useScrollDirection; |
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