#Climb.js
...it goes up.
Climb.js adds a fixed button to the document, fading in and out at certain scroll heights, that will return a user to the top of the current page when clicked.
Download repository and add climb.min.js to the bottom of the document. Modfiy styles within climb_init();.
<button id="climb"></button>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.2.2/jquery.min.js"></script>
<script src="scripts/climb.min.js"></script>
<script>
// icon color, background color, side of window, x-coordinate, y-coordinate, window height to display, animation speed
climb_init('white', '#3F51B5', 'right', 0, 100, 800, 500);
</script>