SQL Server SELECT to JSON function

I would like to output the results of a SELECT statement as a JSON object.

I would like this to be a Function and not a stored procedure!

For example, the below table Users

id    name        active
1     Bob Jones   1
2     John Smith  0

Would be returned like this:

[{"id":1,"name":"Bob Jones","active":1},{"id":2,"name":"John Smith","active":0}]

Thanks in advance.