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| const backTop = () => {
const cubic = value => Math.pow(value, 3)
const easeInOutCubic = value => value < 0.5
? cubic(value * 2) / 2
: 1 - cubic((1 - value) * 2) / 2
const el = document.body
const beginTime = Date.now()
const beginValue = el.scrollTop
const rAF = window.requestAnimationFrame || (func => setTimeout(func, 16))
const frameFunc = () => {
const progress = (Date.now() - beginTime) / 500
if (progress < 1) {
el.scrollTop = beginValue * (1 - easeInOutCubic(progress))
rAF(frameFunc)
} else {
el.scrollTop = 0
}
};
rAF(frameFunc)
}
|
