function debounce(fn, wait) { let timeout = null; return function() { if(timeout !== null) clearTimeout(timeout); timeout = setTimeout(fn, wait); } } const $wrapper = document.getElementById('wrapper') let [x,y] = [0, 0] const halfHeight = ($wrapper.offsetHeight / 2) + 17 const halfWidth = ($wrapper.offsetWidth / 2) + 17 const handle = () => { const scrollTop = document.documentElement.scrollTop || document.body.scrollTop const scrollLeft = document.documentElement.scrollLeft || document.body.scrollLeft if (scrollLeft > x) { if (scrollLeft === halfWidth) console.log('向右滚动到底') else console.log('向右滚动') } else if (scrollLeft < x) { console.log('向左滚动') } if (scrollTop > y) { if (scrollTop === halfHeight) console.log('向下滚动到底') else console.log('向下滚动') } else if (scrollTop < y) { console.log('向上滚动') } x = scrollLeft y = scrollTop } window.addEventListener('scroll', debounce(handle, 200))
