Back to Top in Pure JavaScript

A popular trend you see on many websites is the ''back to top'' button where the user will click this button to automatically scroll back to the top of a page.

In a previous tutorial (Back To Top With jQuery), I revealed how you can do this using jQuery using the animate function to smooth scroll the browser back to the top.

I used this script a lot over the years on multiple new websites I worked on, but recently I've been putting a lot more effort into the performance of websites and working on how you can speed up the page loading times. One of the biggest things I've been working on is removing the need to load jQuery into my application and simply using pure JavaScript.

I know there's a place for jQuery and I won't say you don't need to use it at all, but if all you're doing is simple click events then normally there isn't a need to use jQuery. Therefore, I decided to look again at this jQuery smooth scroll to top function and achieve the same thing by using pure JavaScript and removing the dependency on jQuery.

The HTML

First, you need to have an HTML element on the page for the user to click. This can be a button, a div, or a span, anything that you can add a click event onto.

<div class="back-to-top pointer" onclick="scrollToTop();return false;">Back to top ^</div>

Notice the onclick attribute in the above HTML, this will now run the scrollToTop() function.

For this function, we want to scroll the user back to the top, but to make it look like smooth scrolling, we will need to scroll the page slowly in increments.

First, we check to see if the page is already at the top of the window, if not then we continue with the script.

if (document.body.scrollTop!=0 || document.documentElement.scrollTop!=0)
{

}

We then take the window and scroll -50px to the top of the window.

After scrolling up 50px, we need to set a timeout to repeat this scrollToTop() function every 10 milliseconds. This will create the smooth scroll effect back to the top of the page until it lands back to vertical position 0.