Well if I was interviewing the guy, my second or third question would be "tell me about these packages you published on NPM"
It's going to be damn hard to make an average function sound impressive.
It's going to be damn hard to make an average function sound impressive.
Someone who understands what NPM is, has written and published working code (even stupid code) is miles ahead of the curve already.
Most companies in the world, especially non-software companies, don't go for 5% hacker gurus. Attracting someone vaguely competent is already a blessing.
Interviewed enough "C++, 3 years" people who couldn't even describe a class, or give the most basic description of OO, to have no illusions of some of the standards out there. Similar for other languages. Similar for how much having a degree is worth. I used to be surprised such people tried it on, as there was no way they'd walk out of the hour looking anything but stupid, but it happened often enough to stop surprising. Of course I've also experienced code produced by such types, and worked with a couple.
If you're going to publish something then make the world a better place not pollute it with pointless stuff.
Spending more time publishing this package than most basically competent developers would spend writing the four lines is not going to mark you as "miles ahead of the curve" in my eyes. If you're an 18yo fresh out of school without degree, seeking trainee role, I'd look on it favourably.
I can easily see this grow into a function accepting options indicating such things as "null values are zeroes", "ignore null values", "evaluate string arguments", etc, or maybe into a factory that produces customized averaging functions.
For example, average([null,1,2,3],[4,5]) could either be 3 (the average of all numbers), 2.5 (sum of numbers divided by number of 'root' items), undefined (input format error), 3.25 (average of average of [1,2,3] and average of [4,5]), etc.
And what if it gets passed arrays of equal size? "average([1,2,3],[7,4,5])" could easily be interpreted as a vector average, and produce [4,3,4]
Silly? Yes, but if you want to write a robust library in JavaScript, you have to think about what to do with all these kinds of input.
And of course, there are the simple variants of harmonic mean, arithmetic mean, and geometric mean, and several others (https://en.m.wikipedia.org/wiki/Average)
If an interviewee did respond with some or all of the points you raise he'd have turned a potential negative into a positive point. This instance is the simple arithmetic mean with no consideration of anything.
I stand by my original comment. Nine times out of ten an average is going to be resolutely unexceptional, one time in ten or less it's the core of a well-crafted solution with a decent reason for being.