Reading these things is good advice! But it's distinct from the advice given in the article, which is about reading libraries close to the heart of the language that are written in that language itself.

JS is a bit odd here, possibly for good reasons (ubiquity + dynamic nature of the lang itself might mean runtime considerations override any degree of self-hosting), but it basically means it's not possible for standard definitions of standard library. So the question becomes... what are some masterful libraries written in JS?