Clicked through to https://exploringjs.com/deep-js/ch_type-coercion.html and I have to say that's already a bit questionable. The idea is there, but the writing around it is shaky (if you want to explain coercion, showing JS code without coercion without explaining that's what you're doing is not the best way to explain things to folks looking for answers).

Same for https://exploringjs.com/deep-js/ch_copying-objects-and-array..., the idea is there, but the text isn't great (is it only for objects and arrays? if I'm new to JS but someone taught me about Set and Map, can I assume those always deep copy?).

It's a great start, but it can definitely do with a few QA (rather than editorial) passes.