Back to top button like Facebook app

The Facebook app on Windows phone has a nice and unobtrusive back to top button that only appears once you scroll past a certain point, and only when you start scrolling up the page.

The following code offers similar functionality using jQuery.

HTML

First you need to add the back to top button itself. In this example it's just the text "TOP", but you can replace this with an image or icon font symbol or whatever you want.

This element should be placed just before the closing "body" tag, and not inside any element with "position: relative", unless you want to change how it is positioned.

<a id="scroll-top" href="#" style="display:none;">TOP</a>

Note the href attribute is set to "#". The script below uses jQuery to animate scrolling to the top of the page, but you may wish to use an anchor reference instead here.

CSS

To give the button fixed positioning and place it near the top right corner, you will need some styling. You can change the position if you like.

I've also set the font size to 34 pixels in this example.

#scroll-top {
	position: fixed;
	top: 10px;
	right: 10px;
	font-size: 34px
}

JavaScript

Here's the JavaScript (using jQuery) that shows and hides the button as needed.

I use setInterval so I can track when the user is scrolling up.

Where you see the number "100", this is the number of pixels down from, the top that the button will be displayed after. That way it won't be shown over your header and if the user is near the top of the page they don't really need a back to top button then anyway.

$(function() {
	var lastPos = $(this).scrollTop();

	setInterval(function() {
		var thisPos = $(this).scrollTop();
		if ($(this).scrollTop() > 100 && thisPos < lastPos) {
			$("#scroll-top").show();
		} else {
			if ($(this).scrollTop() <= 100 || thisPos > lastPos) {
				$("#scroll-top").hide();
			}
		}
		lastPos = thisPos;
	}, 150);

	$("#scroll-top").click(function() {
		$("html, body").animate({
			scrollTop: 0
		}, 500);
		return false;
	});
});

Example

Want to see it in action?

Example on JSFiddle