How powerful is Javascript in Storyline?

Hi all experts,

I don't know if this question is a little dumb to ask, but how powerful is javascript in Storyline? I know that Storyline can execute javascript. however, since I am not an expert in javascript, I don't know exactly what we can do with it in Storyline. Can someone give me some examples? I've seen some examples like the system date and random numbers, but can we do some interactions with javascript?

Any feedback would be appreciated! Thanks!

Cheng