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This is very vague. Can you give some examples?
The question asking for clarification is itself vague. Examples of which part? Look at JS that's written for serious applications today, identify the stuff that you'd label as "idiomatic", and then look at code that was written 10 years ago for serious applications, and see if it matches what your conception of "idiomatic JS" is. Good references for the way JS was written for high-quality applications without the neg…
Can you recommend any sources of truth/books that can guide down the right path? Of course I'll be going through all the things you mention but I'm just curious if there's somewhere I can get the right information besides just reading through Firefox code, for example.
Thanks!!!