Using Google Apps Script to check if a website updates

I'm trying to write a google apps script application that continuously saves recorded Xbox game clips to google drive.

I've messed around with "UrlFetchApp.fetch" to check and find content on a webpage.

Here is an example: Google Apps Script to grab data from webpage

var page = UrlFetchApp.fetch('http://oldschool.runescape.com/slu').getContentText();
var number = page.match(/There are currently ([0-9,]+)/)[1];

This is great for getting existing data, but in order for this app to work as designed I want it to continuously check for new content. Even if it checks every so often, it needs to look at the website and see a difference or change in order to run.

My Question: How can I get google apps script to check a website content for a change?

What I'm trying to do:

I want to use, XboxClips.com on a specific user and check for when a new clip is added. That way from there I can download it and add it to google drive.