amrelarabi

function isOnScreen(elem) {
	// if the element doesn't exist, abort
	if( elem.length == 0 ) {
		return;
	}
	var $window = jQuery(window)
	var viewport_top = $window.scrollTop()
	var viewport_height = $window.height()
	var viewport_bottom = viewport_top + viewport_height
	var $elem = jQuery(elem)