File size: 1,297 Bytes
1e92f2d
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
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;