What's engine used in website digitaltrends.com to auto update url when scroll page?

In website digitaltrends.com, I see they can update the page url when scroll down page. If we scroll up, website update again with the page url before. It's so interesting to increase the webview and attract the user to website content.

What're technics used? I try to research with keywords: "automatic update url when scroll website" but find nothing about this.

EXAMPLE: http://ift.tt/1GBnNrW