The firstIndex(...) function has only one variation, not counting syntax variations. It finds the index value of the first element of the Array. The result's data type is the index's data type. If the Array value is null or if the Array contains no elements then the result is null.

Syntax:
firstIndex( array-value )
array-value.firstIndex()

 

Parameter	Description
array-value	The array value who's first index is being found.