Like most CLI programs, Ctags can have its behaviour changed by passing it options like -R, to make it work recursively, or -f badaboom, to make it generate a file called badaboom.
Teaching Ctags about a new language or extending the rules of a supported language is also done with options like --langmap or --regex-<lang>. For example, we could call Ctags with these options:
$ ctags -R --regex-javascript=<regex> --regex-javascript=<regex> [...] --regex-javascript=<regex> .