Fallback operation

The fallback operation provides a default value when something is missing, such as optional attributes or parameters.

To specify a default value, place the ?? operator between the expression you want to check and the fallback value:

user's name ?? "Anonymous"

In the above example, the expression returns either the user's name or "Anonymous" if the user's name is missing.

For a more natural language feel, you can write:

user's name or else "Anonymous"

You can also chain multiple fallback values together to return the first non-absent value:

user's name or else user's nickname or else "Anonymous"

In this case, the expression checks the user's name first, then the nickname, and finally returns the fallback if both are missing.