It's fairly straightforward to use if you are familiar with cron. You simply create an CronJob object constructed with a function and a string that tells when to run it. Since tools like browserify and webpack allow you to package up almost any node package as browser-ready code, it's trivial to set this up to run on a webpage.
Here's a quick script I made as an example. It's a clock that updates every 2 seconds and displays if it is Monday.
If you are developing something on the web where you need to display something to a user at a specific time or on a regular basis, this could be a major help.