isElementInViewport

isElementInViewport.js

function isElementInViewport(el) {
    http://stackoverflow.com/questions/325933/determine-whether-two-date-ranges-overlap
    { /* The source of the following code. */ }
    const rect = el.getBoundingClientRect()
    const windowHeight = (window.innerHeight || document.documentElement.clientHeight)
    const windowWidth = (window.innerWidth || document.documentElement.clientWidth)
	
	
    const vertInView = (rect.top <= windowHeight) && ((rect.top + rect.height) >= 0)
    const horInView = (rect.left <= windowWidth) && ((rect.left + rect.width) >= 0)
	const isElementPartiallyInViewport = vertInView && horInView
    if (isElementPartiallyInViewport) { return true }

    return (
        (rect.left >= 0) &&
        (rect.top >= 0) &&
        ((rect.left + rect.width) <= windowWidth) &&
        ((rect.top + rect.height) <= windowHeight)
    )
}