The problem with this sort of "knowledge map" to track learning a language is that it implies learning the language APIs is the most significant part of learnin

The problem with this sort of "knowledge map" to track learning a language is that it implies learning the language APIs is the most significant part of learning the language. That's really not true though. For example, if a junior developer is working on something that manipulates strings, and they don't know how to test whether a string ends with a particular sequence of characters I don't really care that they've not encountered endsWith yet; that's a Google search away. If they don't know that strings can have different character encodings, byte lengths, locales, etc that's going to affect their entire feature. That's what a dev should learn from a JS course. A JS course should spend several hours on strings, what they do, how they work, and what the pitfalls are, and maybe 5 minutes enumerating the available String functions. Learning to be a developer is a lot more than memorising the standard library (or built-ins in JS's case.) If a course tracks progress by which APIs you've used so far I think that's a sign it might not really be teaching the right stuff.