To be fair, one should note that "only" the languages C, Python, Perl and Tcl [1] are officially supported by PostgreSQL. Also, there are 3rd-party bindings for other languages such as Java, PHP, R, Ruby, Scheme, sh:

http://www.postgresql.org/docs/9.2/interactive/external-pl.h...

However, the PostgreSQL documentation doesn't mention JavaScript support anywhere. Are you sure there exists mature PL/JavaScript binding for PostgreSQL? If so, their docs should be updated.

[1] There's also "pgSQL", but that's a special-purpose language you won't find outside the database world. I don't recommend learning it unless you have strange requirements that make PL/pgSQL a perfect fit. For normale usage, use PL/Python or PL/Perl. In simple cases, use SQL directly.