Infinite Scroll Performance Problem

InfiniteScrollPerfTest.js

function isElementInViewport (rect) {

    return (
        rect.top >= 0 &&
        rect.left >= 0 &&
        rect.bottom <= (window.innerHeight || document.documentElement.clientHeight) && /*or $(window).height() */
        rect.right <= (window.innerWidth || document.documentElement.clientWidth) /*or $(window).width() */
    )
}

function hideIfNotVisible(o){
	
	if(o.visible === false) $(o.el).children().remove();

	return o
}

function createFakeSpace(o){
	$(o.el).css('height', o.rect.height)

	return o
}

$('.lead-table .lead-row')
.map((i, el) => {el, rect: el.getBoundingClientRect()})
.map((i, o) => {
	o.visible = isElementInViewport(o.rect)

	return o
})
.map((i, o) => {
	hideIfNotVisible(o)
	createFakeSpace(o)
	
	return o
})
;