If you come from Javascript, like me, you were probably expecting that when mapping over an array you had access to the index of the item, like so:

myArray.map((item, index) => {
     // whatever
}

Well, the index in Dart is not available. So you will first have to convert the array to a map, with key-value pairs, like so:

myArray.asMap().entries.map((entry) {
    int idx = entry.key; // this is the index
    String val = entry.value;

    return whatever;
}

Don't forget to call asMap, like so: asMap(), and chain entries. If you need the outcome to be a Flutter List, you need to add the toList() at the end.

Kudos to these folks for teaching me this. Dart docs here.