Elevator.js (2015)
A very cute bit of coding.<p>But: I've always wondered who uses these "back to the top" buttons, and why?<p>Until quite recently I hardly ever had reason to go back to the top of the page—I was much more likely to click a link or click the back button—and if I did a quick tap of the home key or flick of the touchscreen usually did the trick.  Conveniently, both gestures work even if you've not gotten all the way down to the "back to the top" button.<p>More recently with Chrome on iOS I find myself wanting to get to the top so I can use the pull-down-then-right gesture to close the tab.  With really long pages sometimes a single flick isn't enough to get me all the way to the top—but then, on a really long page I'm also unlikely to have gotten all the way to the bottom.