When the dashboard is embedded inside another web page, control can be passed back to the hosting application by creating a 'Drillout' component & setting its type to be 'Javascript Function'.
You can also configure additional Javascript functions besides the template function which already exists in the dashboard.html file. It allows for a simple message to show what was clicked (similar to a grid drilldown but easier and quicker to interact with in some cases).
To configure a Javascript drillout
1 Create a component drillout using the drillout icon:
2 Select the Javascript function radio button and type in the default 'DashboardMethod' function: 
3 Next, add an attribute column from the dataset. 
4 You can select Test to ensure the Function works as expected.
The XML in the above screenshot is passed into the javascript method. The elements are:
- ColumnName: This is the name of the column in the dataset 'calling' the drillout
- DataType: The type of the dataset column
- ColumnID: The dashboards internal ID for the column that was clicked
- ComponentID: The dashboards internal ID of the component that was clicked. This can be used if you have multiple components in a dashboard that are JavaScript drillouts
- Values: This can either be a single value or a list of multiple values (comma separated) that were clicked to cause the drillout to be called.