The fact that they're built into the language is in fact significant. Yes, you obviously could implement J's set of primitives in nearly any language and then use those. In practice though, you won't, and if you did then many of the people reading the code wouldn't understand it very well.
Imagine if lodash was built into JS, and optimized by the implementations to the point where it was faster than not using it. Idiomatic JS would look very different even though it hasn't made anything possible that wasn't previously possible.
Imagine if lodash was built into JS, and optimized by the implementations to the point where it was faster than not using it. Idiomatic JS would look very different even though it hasn't made anything possible that wasn't previously possible.