Javascript LaTeX to HTML interpreter?

Javascript LaTeX to HTML interpreter?

Is there a possibility to 'render' latex code with your browser?
I have some *.tex files which I would like to render a HTML version of
(with HTML-navigation, hyperlinks, etc). However - running some tex2html
converter everytime is quite annoying, especially since I use a lot of
special packages that are not supported by most converters I tried so far,
so I would need to post-process the files everytime I change something in
my source document, which happens very often.
What I would really like to have is a javascript library that parses a TeX
file and renders an HTML webpage from it using DOM. It doesn't need to be
complete in the sense that all CTAN packages are supported, but it should
be extendable in the sense that I can plug in my own javascript code to
render some self-defined environments and commands.
So what I'm looking for is a javascript to HTML interpreter. Is there such
a thing, or would I need to write something up myself?
PS: I know about MathJax, which does an excellent job at rendering math,
but I would like to render whole documents, including preamble and custom
command definitions.