# Top 10 List methods you should know

As part of my venture in client-side application development with [Dart, I](https://dartlang.org/) began exploring how one could go about working with Array/List types. Aside from the documentation being comprehensive, I was also able to find support on the [StackOverflow](https://stackoverflow.com/questions/tagged/dart) community and successfully achieved what was needed.

In today’s article we’ll be looking at the “batteries-included” notion of Dart, in particular, the [inbuilt utilities](https://api.dartlang.org/dev/2.0.0-dev.65.0/dart-core/List-class.html) for working with Lists. I’ve hand-picked 10 of the most common ones you show know for your next app. I’ve also [prepared](https://dartpad.dartlang.org/aec9a0ecd000063f53630799bb24b05c) the example snippets so you could play with those yourself :) So, *shall we begin?*

## **1\. forEach()**

Runs a function on each element in the list

```dart
var fruits = ['banana', 'pineapple', 'watermelon'];
fruits.forEach((fruit) => print(fruit));
// => banana pineapple watermelon
```

## **2\. map()**

Produces a new list after transforming each element in a given list

```dart
var mappedFruits = fruits.map((fruit) => 'I love $fruit').toList();
print(mappedFruits);
// => ['I love banana', 'I love pineapple', 'I love watermelon']
```

## **3\. contains()**

Checks to confirm that the given element is in the list

```dart
var numbers = [1, 3, 2, 5, 4];
print(numbers.contains(2)); // => true
```

## **4\. sort()**

Orders the elements in a list based on the provided *ordering* function

```dart
var numbers = [1, 3, 2, 5, 4];
numbers.sort((num1, num2) => num1 - num2); // => [1, 2, 3, 4, 5]
```

## **5\. reduce(), fold()**

Compresses the elements of a list to a single value, using a given function

```dart
var sum = numbers.reduce((current, next) => current + next);
print(sum); // => 15

// with fold() you provide an initial value
const initialValue = 10;
var sum2 = numbers.fold(
  initialValue,
  (current, next) => current + next,
);
print(sum2); // => 25
```

## **6\. every()**

Confirms that every element satisfies the test

```dart
List<Map<String, dynamic>> users = [
  { "name": 'John', "age": 18 },
  { "name": 'Jane', "age": 21 },
  { "name": 'Mary', "age": 23 },
];

var is18AndOver = users.every((user) => user["age"] >= 18);
print(is18AndOver); // => true

var hasNamesWithJ = users.every(
  (user) => user["name"].startsWith('J'),
);
print(hasNamesWithJ); // => false
```

## **7\. where(), firstWhere(), singleWhere()**

Returns a collection of elements that satisfy a test

```dart
// See #6 for users list
var over21s = users.where((user) => user["age"] > 21);
print(over21s.length); // => 1

var nameJ = users.firstWhere(
  (user) => user["name"].startsWith('J'),
  orElse: () => null,
);
print(nameJ); // => {name: John, age: 18}

var under18s = users.singleWhere(
  (user) => user["age"] < 18, orElse: () => null,
);
print(under18s); // => null
```

`firstWhere()` returns the first match in the list, while `singleWhere()` returns the first match provided there is **exactly one match**.

## **8\. take(), skip()**

Returns a collection while including or skipping elements

```dart
var fiboNumbers = [1, 2, 3, 5, 8, 13, 21];
print(fiboNumbers.take(3).toList()); // => [1, 2, 3]
print(fiboNumbers.skip(5).toList()); // => [13, 21]
print(fiboNumbers.take(3).skip(2).take(1).toList()); // => [3]
```

## **9\. List.from()**

Creates a new list from the given collection

```dart
var clonedFiboNumbers = List.from(fiboNumbers);
print('Cloned list: $clonedFiboNumbers');
```

## **10\. expand()**

Expands each element into zero or more elements

```dart
var pairs = [[1, 2], [3, 4]];
var flattened = pairs.expand((pair) => pair).toList();
print('Flattened result: $flattened'); // => [1, 2, 3, 4]

var input = [1, 2, 3];
var duplicated = input.expand((i) => [i, i]).toList();
print(duplicated); // => [1, 1, 2, 2, 3, 3]
```

## Conclusion

I hope this has been insightful and if this is your first exposure to Dart, read my [first steps tutorial](https://dev.to/graphicbeacon/learn-dart-before-you-flutter-2997) to grasp the basics. The example snippets for this article are available on [DartPad](https://dartpad.dartlang.org/aec9a0ecd000063f53630799bb24b05c).

**Like, share and** [**follow me**](https://twitter.com/creativ_bracket) for more content on Dart.

Thanks for reading