FBJS

FBJS is Facebook JavaScript Languages. FBJS is Facebook's solution for developers who want to use Javascript in their Facebook applications. We built FBJS to empower developers with all the functionality they need, and to protect our users' privacy at the same time. Most providers who allow developers to embed Javascript within their domain force developers to use iframes to sandbox their code. Facebook has taken a different approach to this problem. Javascript that you give us will be parsed, and any identifiers (function and variable names) will be prepended with your application id.
FBJS enables you to build deeply integrated Facebook Platform applications in new and interesting ways. FBJS supplies a very powerful AJAX object for developers. Facebook will proxy all AJAX requests and optionally run useful post-processing on the data returned, such as JSON, or FBML parsing. There are also rumors of new functionality to come, such as a data storage API.