Small and focused is good. Keeps from having to import a huge library (e.g., math.js) for simple functions when you don't need what the rest of the library offe

Small and focused is good. Keeps from having to import a huge library (e.g., math.js) for simple functions when you don't need what the rest of the library offers. Small surface. Would I use is-even? No, I'd keep it in a local utility that bundles up other things my specific app needs, or package groups of small util libs into an app-specific uber-module.