For an array of 5-10 items the performance hit of foreach is worth it for readability. Maybe an interesting discussion could occur about when to sacrifice readability for performance but you won’t get that by grilling people about minutiae.
As always it depends, maybe that component is being called 500 times on the page making it actually 5,000 invocations.
I'd FULLY expect a candidate to understand the difference and would ask in a whiteboard session. There is a lot of bloated slow javascript libraries out there and they almost always stem from the fact that most devs don't realize how much overhead function calls introduce.
For the interview, there is no discussion necessary, the correct answer is simply:
"I used a foreach for readability, because performance doesn't matter in this case because X."
or
"I used a for because performance matters in this case because Y"
End of story.
100% agree. my point is more about OP's example being used to prove that dumb questions get asked. if it's being asked by a good interviewer, it's usually relevant.