find the index of item even there is duplication in Dart

I’m really confused on how I’m gonna find the index of item in array where there’s a lot of duplicated words.

List<String> _words = "the quick brown fox jumps over the lazy dog".split(" ");

now I want to get the all the index in word "the" programmatically.

I expect a result of

List indexOfWords = _words.indexOfAll("the");
print(indexOfWords);

// [0, 6]

>Solution :

You can define indexOfAll as an extension method. I would implement it like this:

extension ListExtension<T> on List<T> {
  List<int> indexOfAll(T item) => [
        for (int i = 0; i < length; i++)
          if (this[i] == item) i,
      ];
}