POMjs is a random password generator in HTML and pure Javascript. It can be customized by modifying the sources. There's really nothing magic going on here, but it works and is somewhat responsive. The goal was to make something small, useful, and reasonably free from dependencies.
POMjs includes no externally loaded resources and contains no tracking code or cookie management.
POMjs is released as open source (GPLv2).
You can find the official repo on github.com/joho1968/POMjs
You can also use password.oppetmoln.se to see POMjs in action.