If Unknown checks whether a value is unknown. If so, the result is a second value. If the value is not unkown, that value is returned.
Syntax
Value1 ? Value2
Returns
Returns Value2 if Value1 is unknown. Otherwise Value1 is returned.
Examples
text ? "Please enter a value"
/* If `text` is unknown then the result is "please enter a value". If `text` is not unknown then `text`' is the result. */
