Class for managing items with parallax scroll

parallax-scroll

function ParallaxScroll() {
	this.$window = $(window);
	this.items = new Array();
	
	this.init = function() {
		this.$window.scroll(doParallax);
	}
	
	var doParallax = function() {
		// Check we have any items before we do any scolling
		var items = window.parallaxScroll.items;
		if (items == undefined || items.length < 1) return false;
		
		// Alright, we've got items. Continue:
		var $w 		= window.parallaxScroll.$window,  
			amount	= $w.scrollTop();
		
		for (var i in items) {
			var val = Math.round(amount * items[i].p);
			items[i].el.css('top', (val > 0)? val : 0);
		}
	}
	
	this.addItem = function($el, parallax) {
		this.items.push({el: $el, p: parallax});
		doParallax();
	}
}