export function handleScrollHeader (callback) {
let timer = 0
let beforeScrollTop = window.pageYOffset
callback = callback || function () {}
window.addEventListener(
'scroll',
event => {
clearTimeout(timer)
timer = setTimeout(() => {
let direction = 'up'
const afterScrollTop = window.pageYOffset
const delta = afterScrollTop - beforeScrollTop
if (delta === 0) {
return false
}
direction = delta > 0 ? 'down' : 'up'
callback(direction)
beforeScrollTop = afterScrollTop
}, 50)
},
false
)
}