One question to ask yourself is why a front-end developer would be asked to do this on an extremely large data set? I think any experienced front-end developer is going to know that if the data set is large enough you need to care about writing specific forms of loops for optimization, that’s going to be done on the back end. While potentially we could be talking about a node.js backend, I don’t think that’s the common case we’d be talking about here.

So I think most interviewers would be biased toward the solution that gets the job done and is easiest to maintain — the 3-line solutions that leverage the Array’s built-in functionality. I think if you walked through the kind of complex discussion you gave above to what is actually a simple project, most employers are going to assume you will waste a lot of everyone’s time overthinking everything.