The Action Context uses a mechanism called addons to provide functionality that lives both on the server and client. Each addon provides additional functions through a namespacing object, which is appended to the ActionContext object that is available in every controller function. See the ActionContext Class for the addon classes.
Addons allow you to do the following:
Using the ActionContext object ac, you would call a {method} from an {addon} with the following syntax:
ac.{addon}.{method}
For example, to get all of the query string parameters, you would use the Params addon with the url method as seen here:
ac.params.url()
The following code examples use the addons in parentheses:
Because customized addons are not part of the standard API, but an extension of the API, the instructions for creating addons can be found in Creating New Addons.