Scrolling “Go To Top” Link Using Dojo

One of the most popular code snippets of posted on my blog has been the scrolling "Go To Top" link snippet. The premise of the snippet is simple: once the user scrolls an element (usually the BODY element) past a given threshold, a "Go To Top" anchor fades into view. Simple, stylish, and functional -- the definition of a good JavaScript-powered enhancement. I've showed you how to accomplish this task using jQuery and MooTools; here's how you can accomplish that same effect using Dojo.

The HTML

<a href="#top" id="gototop" class="no-click no-print">Top of Page</a>
<!-- you could also create this dynamically using dojo -->

Just a simple "top" link.

The CSS

	#gototop { visibility:hidden; position:fixed; right:5px; bottom:5px; color:#999; font-weight:bold; text-decoration:none; border:1px solid  #ccc; background:#eee; padding:10px; }

It's important to hide the element during the initial page load.

The Dojo JavaScript

dojo.ready(function() {
	var link = dojo.byId("gototop");
	dojo.style(link,{ opacity: 0, visibility:"hidden" });
	dojo.connect(window,"onscroll",function(e) {
		var scrollY = -dojo.position(dojo.body()).y, thresh = 100;
		dojo.anim(topLink, { opacity: (scrollY > thresh ? 1 : 0 ) });
	});
});

When the DOM is ready we grab the link, styling it so that it will hidden via visibility instead of display. On each scroll of the body, we calculate the position of the page and show or hide the link depending on the page position. Easy!

There you have it. Another framework, another flavor of JavaScript, another awesome snippet. Happy scrolling!