Config.js allows developers to configure their applications in an XML block instead of hard-coding values inside their scripts. It can also be used to store HTML templates instead of hardcoding HTML into JavaScript. The XML can be embedded inside an HTML document or in a separate XML file. The configuration block may contain strings, numbers, arrays and HTML. Furthermore, variables can be inserted into these values, allowing developers to use the XML block as a simple templating system for their applications.
http://www.useragentman.com/blog/config-js-%E2%80%93-a-javascript-cofiguration-library/