There is a new JS Lang target for ANTLR4 that was posted to GitHub almost 3 months ago:
It's not integrated into an official release yet, but you can probably just throw it into the latest ANTLR4 codebase and recompile ANTLR yourself.
I have been trying to get this working, and have only just managed to generate .js files succesfully after reading this:
From the post:
From then on you can use ANTLRWorks 1.2.2 to generate the lexer and parser code by selecting "Generate Code" from the "Generate" menu. ANTLRWorks will place the generated files into an
outputdirectory in the folder in which the grammar file resides.
Note that if an error occurs in the generation process, then for some reason the "Generate Code" action no longer works. Simply close the grammar and re-open it from the "Open Recent" menu.