I agree with your general sentiment, but Array.isArray() has been standard since about 2010. It’s even in IE9. Anyone using an npm package for this feature deserves the beating.

IMO the problem with npm is that it makes no distinction between snippets, libraries, frameworks and scripted command line tools. An npm package can be any of these. I feel there perhaps should be separate namespaces and package managers for all four — e.g. an inlining minimal “node snippet manager”, a standardized framework installer for things like create-react-app, and so on.