How to use eval

Question

Can someone give me an example of how to use it?

Answer 1

https://code.sololearn.com/WL6ZFKF9JyEv/?ref=app

Answer 2

Not just maths
Any js scripts
You use in situation like in this tutorial:
https://code.sololearn.com/WiigcSaKlUx7/?ref=app

Answer 3

Where it might be used?
I mean, in which context should i choose this method for mathematical operations instead of any other simpler method?