> (And frankly, I just had to look up what !! does, despite years of writing JS code.)
It's literally just 2 NOT operators chained together. I won't fault you for never having seen it, but it is curious considering how common it is.
In any case. Looking that up just made you a more knowledgeable JavaScript developer, while looking up some random lodash function won't buy you much at all.
I'm not sure why you'd think learning a little about widely-used JS libraries wouldn't make you "a more knowledgeable JavaScript developer".
Honestly? It probably does. Much less so than learning the actual language built-ins first, but it does. I'm just biased because I consider them more of a pain than anything because of my personal experience with them.
Memorizing multiplication up to 100 will also make you faster at calculating stuff in your head, but I couldn't ever be bothered to do that either.
Sure it does. You've just already read the documentation for filter.
(And frankly, I just had to look up what !! does, despite years of writing JS code.)