Extensions allow Fauxton views to be have extra functionality.

A module registers an extension by

FauxtonAPI.registerExtension('extensionName', myObjectToRegister);

Any other module wanting to use that extension can then get all objects registered for an extension by:

var extensions = FauxtonAPI.getExtensions('extensionName');
// extensions will always be an array

The module can then use those extensions to extend its functionality. An example of extensions in the compaction module (app/addons/compaction/base.js) and in documents module (app/modules/documents/views line 1003)