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Page scrolling in vanilla JavaScript
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// https://pawelgrzybek.com/page-scroll-in-vanilla-javascript/ | |
function scrollIt(destination, duration = 200, easing = 'linear', callback) { | |
const easings = { | |
linear(t) { | |
return t; | |
}, | |
easeInQuad(t) { | |
return t * t; | |
}, | |
easeOutQuad(t) { | |
return t * (2 - t); | |
}, | |
easeInOutQuad(t) { | |
return t < 0.5 ? 2 * t * t : -1 + (4 - 2 * t) * t; | |
}, | |
easeInCubic(t) { | |
return t * t * t; | |
}, | |
easeOutCubic(t) { | |
return (--t) * t * t + 1; | |
}, | |
easeInOutCubic(t) { | |
return t < 0.5 ? 4 * t * t * t : (t - 1) * (2 * t - 2) * (2 * t - 2) + 1; | |
}, | |
easeInQuart(t) { | |
return t * t * t * t; | |
}, | |
easeOutQuart(t) { | |
return 1 - (--t) * t * t * t; | |
}, | |
easeInOutQuart(t) { | |
return t < 0.5 ? 8 * t * t * t * t : 1 - 8 * (--t) * t * t * t; | |
}, | |
easeInQuint(t) { | |
return t * t * t * t * t; | |
}, | |
easeOutQuint(t) { | |
return 1 + (--t) * t * t * t * t; | |
}, | |
easeInOutQuint(t) { | |
return t < 0.5 ? 16 * t * t * t * t * t : 1 + 16 * (--t) * t * t * t * t; | |
} | |
}; | |
const start = window.pageYOffset; | |
const startTime = 'now' in window.performance ? performance.now() : new Date().getTime(); | |
const documentHeight = Math.max(document.body.scrollHeight, document.body.offsetHeight, document.documentElement.clientHeight, document.documentElement.scrollHeight, document.documentElement.offsetHeight); | |
const windowHeight = window.innerHeight || document.documentElement.clientHeight || document.getElementsByTagName('body')[0].clientHeight; | |
const destinationOffset = typeof destination === 'number' ? destination : destination.offsetTop; | |
const destinationOffsetToScroll = Math.round(documentHeight - destinationOffset < windowHeight ? documentHeight - windowHeight : destinationOffset); | |
if ('requestAnimationFrame' in window === false) { | |
window.scroll(0, destinationOffsetToScroll); | |
if (callback) { | |
callback(); | |
} | |
return; | |
} | |
function scroll() { | |
const now = 'now' in window.performance ? performance.now() : new Date().getTime(); | |
const time = Math.min(1, ((now - startTime) / duration)); | |
const timeFunction = easings[easing](time); | |
window.scroll(0, Math.ceil((timeFunction * (destinationOffsetToScroll - start)) + start)); | |
if (window.pageYOffset === destinationOffsetToScroll) { | |
if (callback) { | |
callback(); | |
} | |
return; | |
} | |
requestAnimationFrame(scroll); | |
} | |
scroll(); | |
} |
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