I feel like I have to remind people of this quite often, but the history is such that npm was lightweight at one point, bundling wasn't a thing, and while `isodd`/`iseven` are of course silly, things like `isarray` were not functions that existed back then (we didn't have Array.isArray). `typeof [] === 'object'` in JS, so e.g. my package `is-arrayish` checked for a similar structure to an array (whereas Id guess `isarray` checked for the prototype). `isarray` failed for the `arguments` keyword, which was needed for variadics before argument spreads were added to the language I believe in ES5.
So of course they don't make sense now. But they were created for a reason. Before even Markov chains were a fad - let alone LLMs - we were trying to be as efficient as possible and maximize code reuse I stead of writing the same helper functions over and over again. That's what you're seeing.