Dart Beginner Lesson 32 of 107 5 min read

Dart List Methods: Complete Guide with Easy Examples

All the Dart list methods you need, with runnable examples: add, insert, remove, contains, indexOf, where, map, reduce, fold, sort, sublist, toSet and more.

On this page

The Lists lesson introduced the List type. This page collects the list methods you will reach for every day, grouped by what you want to do, each with a short program and its output. Press Run on any example, change the numbers, and run it again.

Quick reference table

Method	What it does	Changes the list?
`add(x)` / `addAll(xs)`	Add to the end	Yes
`insert(i, x)` / `insertAll(i, xs)`	Add at a position	Yes
`remove(x)` / `removeAt(i)` / `removeLast()`	Remove one item	Yes
`removeWhere(test)` / `retainWhere(test)`	Remove by condition	Yes
`clear()`	Remove everything	Yes
`sort()` / `shuffle()`	Reorder	Yes
`contains(x)` / `indexOf(x)`	Find an item	No
`firstWhere(test)` / `indexWhere(test)`	Find by condition	No
`any(test)` / `every(test)`	Check a condition	No
`where(test)`	Keep matching items	No (new iterable)
`map(f)`	Transform each item	No (new iterable)
`reduce(f)` / `fold(start, f)`	Combine into one value	No
`sublist(a, b)` / `take(n)` / `skip(n)`	Get part of the list	No
`join(sep)`	Make one string	No
`toSet()`	Remove duplicates	No

Methods such as where, map, take and skip return a lazy Iterable. Add .toList() when you need a real list back. The Iterable lesson explains why.

Creating lists

void main() {
  var empty = <String>[];
  var zeros = List.filled(3, 0);
  var squares = List.generate(5, (i) => i * i);
  var a = [1, 2];
  var b = [3, 4];
  var both = [...a, ...b];

  print(empty);
  print(zeros);
  print(squares);
  print(both);
}

[]
[0, 0, 0]
[0, 1, 4, 9, 16]
[1, 2, 3, 4]

Adding items

void main() {
  var nums = [1, 2, 3];

  nums.add(4);
  nums.addAll([5, 6]);
  nums.insert(0, 0);
  nums.insertAll(2, [10, 20]);

  print(nums);
  print(nums.length);
}

[0, 1, 10, 20, 2, 3, 4, 5, 6]
9

Removing items

void main() {
  var n = [5, 10, 15, 20, 25, 30];

  print(n.remove(10));     // true: it was found
  print(n.removeAt(0));    // returns the removed item
  print(n.removeLast());
  n.removeWhere((x) => x > 20);
  print(n);

  var m = [1, 2, 3, 4, 5, 6];
  m.retainWhere((x) => x.isEven);  // keep only even numbers
  print(m);

  m.clear();
  print(m.isEmpty);
}

true
5
30
[15, 20]
[2, 4, 6]
true

Finding items

void main() {
  var langs = ['Dart', 'Kotlin', 'Swift', 'Dart'];

  print(langs.contains('Swift'));
  print(langs.indexOf('Dart'));
  print(langs.lastIndexOf('Dart'));
  print(langs.indexWhere((l) => l.startsWith('S')));
  print(langs.firstWhere((l) => l.length > 4));
  print(langs.firstWhere((l) => l == 'Go', orElse: () => 'none'));
  print(langs.any((l) => l == 'Java'));
  print(langs.every((l) => l.isNotEmpty));
}

true
0
3
2
Kotlin
none
false
true

Without orElse, firstWhere throws a StateError when nothing matches.

Transforming: where, map, reduce and fold

void main() {
  var prices = [120, 45, 300, 80];

  print(prices.map((p) => p * 2).toList());
  print(prices.where((p) => p > 100).toList());
  print(prices.reduce((a, b) => a + b));
  print(prices.fold(0, (sum, p) => sum + p));
  print(prices.map((p) => '\$$p').join(', '));
}

[240, 90, 600, 160]
[120, 300]
545
545
$120, $45, $300, $80

reduce fails on an empty list; fold does not, because you give it a starting value. There is a full lesson on where, map, reduce and fold.

Sorting and reversing

void main() {
  var scores = [42, 7, 19, 3];

  scores.sort();
  print(scores);

  scores.sort((a, b) => b.compareTo(a)); // biggest first
  print(scores);

  print(scores.reversed.toList());

  var words = ['banana', 'fig', 'apple'];
  words.sort((a, b) => a.length.compareTo(b.length)); // shortest first
  print(words);
}

[3, 7, 19, 42]
[42, 19, 7, 3]
[3, 7, 19, 42]
[fig, apple, banana]

shuffle() puts the items in a random order, which is useful for quiz and card games.

Getting part of a list

void main() {
  var l = [1, 2, 3, 4, 5, 6];

  print(l.sublist(2));
  print(l.sublist(1, 4));
  print(l.take(3).toList());
  print(l.skip(4).toList());
  print(l.takeWhile((x) => x < 4).toList());
  print(l.getRange(1, 3).toList());
  print(l.first);
  print(l.last);
}

[3, 4, 5, 6]
[2, 3, 4]
[1, 2, 3]
[5, 6]
[1, 2, 3]
[2, 3]
1
6

Useful extras

void main() {
  var withDuplicates = [3, 1, 3, 2, 1];
  print(withDuplicates.toSet().toList()); // keeps first appearance order

  var f = List.filled(5, 0);
  f.fillRange(1, 3, 9);
  print(f);

  print(['a', 'b'].asMap());

  for (final (i, v) in ['red', 'green'].indexed) {
    print('$i: $v');
  }
}

[3, 1, 2]
[0, 9, 9, 0, 0]
{0: a, 1: b}
0: red
1: green

indexed gives you each position and value together. It uses a record pattern, a Dart 3 feature.

A small real example: student marks

void main() {
  var marks = [72, 45, 91, 38, 84];

  var passed = marks.where((m) => m >= 40).toList();
  var total = marks.fold(0, (sum, m) => sum + m);
  var average = total / marks.length;
  var highest = marks.reduce((a, b) => a > b ? a : b);

  var sorted = [...marks]..sort();

  print('Passed: $passed');
  print('Average: ${average.toStringAsFixed(1)}');
  print('Highest: $highest');
  print('Sorted: $sorted');
  print('Original is unchanged: $marks');
}

Passed: [72, 45, 91, 84]
Average: 66.0
Highest: 91
Sorted: [38, 45, 72, 84, 91]
Original is unchanged: [72, 45, 91, 38, 84]

[...marks]..sort() copies the list first, so sorting does not change the original. The .. is the cascade operator.

Common mistakes

Forgetting .toList(). print(l.take(2)) prints (1, 2) with round brackets because it is an Iterable, not a List.
Changing a list while looping over it. Removing items inside for (var x in list) throws an error. Use removeWhere instead.
Calling reduce on an empty list. It throws. Use fold with a start value.
Adding to a fixed-length list. List.filled(3, 0).add(1) throws. Pass growable: true if you need to grow it.

Try it yourself

Start with var cities = ['Pokhara', 'Toronto', 'Sydney', 'Delhi', 'Lisbon']; and:

Sort the cities alphabetically.
Print only the cities with more than five letters.
Print the cities in capitals joined with , .
Check whether any city starts with L.