I would say that it's not in wide, generic usage, but rather in wide, implicitly-specific usage.

That is, "generic usage" refers to things like people using "a kleenex" to refer to any facial tissue or "a xerox" to refer to any mimeograph. However, when people say "JavaScript", they always mean the exact same JavaScript: the one Oracle owns.

(It could be argued that they mean ECMAscript—but that's a bit like saying that people who say "pass me a coke" when what they have available are cans of no-name generic cola (with trade-dress explicitly reminiscent of Coca-Cola's, no less) are actually thinking they want any generic cola, rather than that they want a Coca-Cola and that the can you have to offer is merely an adequate stand-in.