I need an idea for a JS coding challenge for a job interview that a poor unlucky person is going to take after me, 'cause i'm leaving..

Requirements: it must be simple, but not simple enough for my other two colleagues. Aka no webpack, no framework, plain js inside a webpage.

My other two colleagues don't even know how to do an array.forEach() or literally how to code in general. They are copy-pastah programmers.

How can i do that without offending anyone?