Javascript has been considered for long time to be a hack language for web pages, with lack of object orientation and too lazy syntax. Recent explosion of ajax "web 2.0" rich internet application demonstrates that javascript is a mature platform, with powerfull libraries and talentuous developers.
Java development uses tools like Ant and Maven to handle project lifecycle and integrate build, documentation and reporting tools. Javascript also has various tools, but no real consensus on how to manage a javascript project. In particular, javascript development as part of a JEE web application should integrate well with exiting java tools.
The javascript maven project provides maven plugins and extensions dedicated to javascript development, either as standalone pure javascript librairies or as part of web application. Its goal is to promote best development practices with a standardized project organization, so that developers can be quickly productive on a project and take advantage of the best tools available for javascript development, documentation or quality assurance.