JavaScript is a scripting language primarily used in website development. However, inside PDI, you use just the core language—you don't run a web browser and you don't care about HTML. There are many available JavaScript engines. PDI uses the Rhino engine from Mozilla. Rhino is an open source implementation of the core JavaScript language; it doesn't contain objects or methods related to the manipulation of web pages.
If you are interested in getting to know more about Rhino, follow this link:
https://developer.mozilla.org/en/Rhino_Overview
The core language is not too different from other languages that you might know. It has basic statements, block statements (statements enclosed by curly brackets), ...
