Created
May 27, 2016 15:49
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var docElem = window.document.documentElement; | |
function getViewportH() { | |
var client = docElem['clientHeight'], | |
inner = window['innerHeight']; | |
if( client < inner ) | |
return inner; | |
else | |
return client; | |
} | |
function scrollY() { | |
return window.pageYOffset || docElem.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 inViewport( el, h ) { | |
var elH = el.offsetHeight, // Heght of element | |
scrolled = scrollY(), // How much the window has scrolled | |
viewed = scrolled + getViewportH(), // whats in view = how much we have scrolled + height of viewport | |
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; | |
} | |
inViewport("Some Div Element", 1); | |
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