scroll-distance.js

const scrollDistance = (callback, refresh) => {
	if (!callback || typeof callback !== 'function') return

	let isScrolling, start, end, distance

	window.addEventListener('scroll', event => {
		if (!start) {
			start = window.pageYOffset
		}

		window.clearTimeout(isScrolling)

		isScrolling = setTimeout(() => {
			end = window.pageYOffset
			distance = end - start

			callback(distance, start, end)

			start = null
			end = null
			distance = null

		}, refresh || 66)
	}, false)
}

scrollDistance(distance => {
	console.log('You travelled ' + parseInt(Math.abs(distance), 10) + 'px ' + (distance < 0 ? 'up' : 'down'))
})