Most of the extensions into Selenium API are done via extending JavaScript from the core of Selenium.

The process of extending is done by loading of ordered set of scripts and injecting into DOM of Test Runner window.

Besides loading the script, SeleniumExtensions are also able to refresh (reload) the script with new definition, which is a great feature in development process.

Only step needed to load or reload script is specifying that the given script resource is required, using SeleniumExtensions#requireScript(String resourceName).