window.addEventListener('scroll', event => {
console.log('x:', window.scrollX)
console.log('y:', window.scrollY)
})
elem.addEventListener('scroll', event => {
console.log('x:', event.target.scrollLeft)
console.log('y:', event.target.scrollTop)
})
このとき取得できるのは要素の左上を(0, 0)とした相対座標.
elem.addEventListener('scroll', event => {
const dx = event.target.scrollLeft / (event.target.scrollWidth - event.target.clientWidth)
const dy = event.target.scrollTop / (event.target.scrollHeight - event.target.clientHeight)
console.log('dx:', dx)
console.log('dy:', dy)
})