This is the API documentation for the Javascript language module used by mod-lang-dynjs and mod-lang-rhino.
Vert.x is a lightweight, high performance application platform for the JVM that's designed for modern mobile, web, and enterprise applications. You're able to write applciations in several languages, including Java, Ruby, Python, Clojure, Scala, and of course Javascript.
More general information about the Vert.x project can be found on the Vert.x site, and for an overview of Javascript usage, see the Javascript API Manual.