The following snippet demonstrates how to access the iteration index when using List.map. It is a common need in Flutter when looping over or mapping a list of values to widgets. Problem Unlike JavaScript, one cannot simply access the index of a list during a List.map operation in Dart. file_type_dartlang main.dart List myList = ['a', 'b', 'c']; myList.map( (val, index) { // This does not work! // Which index am I on? }) Solutions There are several ways to access the index when looping over a List. Use Map Entries Convert the List to a Map, then map the entries containing the key/value pairs. Each key in the map is the index of the original list. file_type_dartlang main.dart myList.asMap().entries.map((entry) { int idx = entry.key; String val = entry.value; return something; } Generate a Fixed Range List If you are looping over many lists that have a fixed length, it may be more efficient to generate a single list once. For example, the we create a ranged list that is the same length as the original, i.e. [0, 1, 2, ..., n] final List fixedList = Iterable<int>.generate(myList.length).toList(); fixedList.map((idx) { String val = myList[idx]; return something; } Grab the Index of Unique Values You can access the index of a specific value by searching for it with List.indexOf, which returns the index of the first match. This approach is most predictable when all values are unique. A Set can ensure uniqueness throughout the list. final List uniqueList = Set.from(myList).toList(); uniqueList.map((val) { String idx = uniqueList.indexOf(val); return something; } Q&A Chat