Fixed sidebar on scrooll with little jquery

fixe-sidebar.js

function FixedSidebar(sidebarName) {
	var self = this;
	this.elSidebar = document.getElementById(sidebarName);
	this.elContent = this.elSidebar.parentNode;
	this.elBody    = document.getElementsByTagName('body')[0];

	this.lastBodyHeight    = this.elBody.clientHeight;
	this.lastSidebarHeight = this.elSidebar.clientHeight;
	this.lastContentHeight = this.elContent.clientHeight;

}

FixedSidebar.prototype = {
	verifyChange : function (self, callback) {
		if(self.elBody.clientHeight != self.lastBodyHeight) {
			self.lastBodyHeight = self.elBody.clientHeight;
			callback(self);
		} else if(self.elSidebar.clientHeight != self.lastSidebarHeight) {
			self.lastSidebarHeight = self.elSidebar.clientHeight;
			callback(self);
		// } else if(self.elContent.clientHeight != self.lastContentHeight) {
		// 	self.lastContentHeight = self.elContent.clientHeight;
		// 	callback(self);
		}
	},
	listenHeightChange : function () {
		var self = this;
		setInterval(function () {
			self.verifyChange(self, self.updateVar);
		}, 100);
	},
	onScroll : function () {
		var self = this;
		window.addEventListener('scroll', function () {
			self.run(self);
		});
	},
	onHeightChange : function () {
	 	window.addEventListener('heightChange', this.updateVar);
	},
	updateVar : function (self) {
		$(self.elSidebar).removeClass('fixed');
		$(self.elSidebar).css('marginTop', '');
		$(self.elSidebar).css('width', '');

 		self.parent = {
			top    : self.elContent.offsetTop,
			bottom : self.elContent.offsetHeight + self.elContent.offsetTop,
			height : self.elContent.offsetHeight
		};

		self.child = {
			top    : self.elSidebar.offsetTop,
			bottom : self.elSidebar.offsetHeight + self.elSidebar.offsetTop,
			width  : self.elSidebar.offsetWidth,
			height : self.elSidebar.offsetHeight
		};

		self.run(self);
		
	},
	run : function (self) {
		var cursor = (window.scrollY - self.parent.top) > 0 ? window.scrollY - self.parent.top : 0;
			cursorBottom = window.scrollY + window.innerHeight;
		
		if (cursorBottom < self.parent.top) { // se não tiver visivel na parte de cima
			var log = 'nao visivel';
			$(self.elSidebar).removeClass('fixed');
			$(self.elSidebar).css('width', '');
			$(self.elSidebar).css('marginTop', '');
		} else if (window.scrollY + window.innerHeight > self.child.bottom) {
			var limitMargin  = self.parent.height - self.child.height;
			var marginAtual  = (cursor + window.innerHeight) - self.child.height - 10;

			if(marginAtual < limitMargin) {
				var log = 'ja é para esta fixo';
				$(self.elSidebar).addClass('fixed');
				$(self.elSidebar).css('width', self.child.width + 'px');
			} else {
				$(self.elSidebar).removeClass('fixed');
				$(self.elSidebar).css('marginTop', limitMargin + 'px');
				$(self.elSidebar).css('width', '');
				var log = 'pare em baixo';
			}
		} else {
			$(self.elSidebar).removeClass('fixed');
			$(self.elSidebar).css('marginTop', '');
			$(self.elSidebar).css('width', '');
				var log = 'normal';
			
		}
	},
	doMagic : function () {
		var self = this;
		this.updateVar(this);
		this.onScroll();
		this.onHeightChange();
		this.listenHeightChange();
	},
}

var magic = new FixedSidebar('sidebar').doMagic();