Фиксированный блок при скролле

function_scroll.js

document.addEventListener("DOMContentLoaded", function() {

	function scrollWidget(){
		var widget 					= document.getElementById('villa-calendar-wrapper'),
			headerHeight 			= document.getElementById('header-outer').offsetHeight,
			widgetPositionParams 	= widget.getBoundingClientRect(),
 			scrollHeight 			= window.pageYOffset || document.documentElement.scrollTop;

		if(widgetPositionParams.top < scrollHeight){
			widget.style.top = headerHeight + 20 + 'px';
			widget.classList.add('fixed');
		} 
		else{
			widget.classList.remove('fixed');
		}
 	}

 	scrollWidget();

	window.onscroll = function(){
		scrollWidget();
	}

});