in JS (and years before that, PHP), one example was object-oriented programming / classes, except in both JS and PHP it was never implemented fully, with JS not even having access modifiers for a long time. JS didn't need classes and the implementation is lacking, but someone decided it should be added.
Likewise, Java had functional programming bolted on; they never extended the base List types with functional modifiers, so now you have to transform or wrap your List in a Stream to make it work with Java's attempts at functional programming. Personally, I think if you want to do FP or FP-style coding on the JVM, you should rewrite things in Scala. You can write Scala and Java side-by-side.
Same with JS, you want JS but with types? You can have Typescript. I wish they did the same with JS-with-classes, just write a new language that compiles to JS instead of bolt classes onto the JS standard.