index

Variables
/
index
Returns the index of the current item in the list function, starting from 0.
Accepts
List
Returns
Number
Syntax
index

In the following example, we first use current to return the values of the original list (1, 2, 3) and then add the index value (0, 1, 2) to each of those. The result is a new list of numbers: 1, 3, 5

JavaScript 
[1, 2, 3]
    .map( 
        current + index
    )