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isExposure.js
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isExposure.js
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// from https://github.com/codrops/GridLoadingEffects/blob/master/js/AnimOnScroll.js
var docElement = window.document.documentElement;
function getViewportH() {
var inner = window.innerHeight;
var client = docElement.clientHeight;
return client < inner ? inner : client;
}
function getScrollY() {
return window.pageYOffset || docElement.scrollTop;
}
// http://stackoverflow.com/a/5598797/989439
function getOffset( el ) {
var offsetTop = 0, offsetLeft = 0;
do {
if ( !isNaN( el.offsetTop ) ) {
offsetTop += el.offsetTop;
}
if ( !isNaN( el.offsetLeft ) ) {
offsetLeft += el.offsetLeft;
}
} while( el = el.offsetParent )
return {
top : offsetTop,
left : offsetLeft
}
}
function isExposure( el, h ) {
var elH = el.offsetHeight,
scrolled = getScrollY(),
viewed = scrolled + getViewportH(),
elTop = getOffset(el).top,
elBottom = elTop + elH,
// if 0, the element is considered in the viewport as soon as it enters.
// if 1, the element is considered in the viewport only when it's fully inside
// value in percentage (1 >= h >= 0)
h = h || 0;
return (elTop + elH * h) <= viewed && (elBottom - elH * h) >= scrolled;
}
export default isExposure