indexOf
Returns the index of the first equal element, or -1 when no element matches.
Indexes follow iteration order and start at zero. Equality uses element == value. Stops at the first match. Exceptions from iteration propagate to the caller.
Receiver
elements to visit in their iteration order.
Return
the matching index, or -1 when empty or unmatched.
Parameters
element
value to search for, including null for nullable element types.
Throws
if a visited element index would exceed Int.MAX_VALUE.