I installed emacs prelude in cygwin via the simple curl installation. I open a test.js file and try typing "document." to see autocomplete but nothing pops up. Admittedly I'm totally an emacs/prelude newbie, is there something else I should be doing to get it to autocomplete?
Does your Prelude installation include library Autocomplete? And is that what you mean by "autocomplete"?
Give a recipe showing what keys you hit and what you expected to happen vs what actually happened.
Consult the Prelude manual.
Ask the preluddites themselves (sorry; couldn't resist): emacs-prelude@googlegroups.com.
I see only a few Google hits in English for all three keywords: "emacs prelude autocomplete", and none of them mention using Prelude and Autocomplete together.