Class DefaultMap<K, V, D>

A Map that has a default value for missing keys.

Example

const map = new DefaultMap(0);

map.get('a'); // 0

Example

const map = new DefaultMap(key => key.toUpperCase());

map.get('a'); // 'A'

Map

Type Parameters

K
V
D extends V = V

Hierarchy (View Summary)

Map<K, V>
- DefaultMap
  - MathMap

Index

Constructors

constructor

new DefaultMap<K, V, D = V>(
defaultValue: Exclude<D, AnyFunction>,
entries?: Iterable<readonly [unknown, unknown], any, any> | null,
): DefaultMap<K, V, D>
Create a new DefaultMap with a specified default value.

Time complexity: O(n)

Space complexity: O(n)
Type Parameters
- K
- V
- D = V
Parameters
- defaultValue: Exclude<D, AnyFunction>
  The default value to use for missing keys
- Optionalentries: Iterable<readonly [unknown, unknown], any, any> | null
Returns DefaultMap<K, V, D>
Example
```
const map = new DefaultMap(0);
```
Overrides Map<K, V>.constructor
- Defined in src/map/default-map.ts:39
new DefaultMap<K, V, D = V>(
defaultValueFunction: (key: K) => D,
entries?: Iterable<readonly [unknown, unknown], any, any> | null,
): DefaultMap<K, V, D>
Create a new DefaultMap with a specified function to generate default values.

Time complexity: O(n)

Space complexity: O(n)
Type Parameters
- K
- V
- D = V
Parameters
- defaultValueFunction: (key: K) => D
- Optionalentries: Iterable<readonly [unknown, unknown], any, any> | null
Returns DefaultMap<K, V, D>
Example
```
const map = new DefaultMap(key => key.toUpperCase());
```
Overrides Map<K, V>.constructor
- Defined in src/map/default-map.ts:54

Properties

`Readonly`[toStringTag]

"[toStringTag]": string

`Readonly`size

size: number

Returns

the number of elements in the Map.

`Static` `Readonly`[species]

"[species]": MapConstructor

Methods

[iterator]

"[iterator]"(): MapIterator<[K, V]>
Returns an iterable of entries in the map.

Returns MapIterator<[K, V]>
Inherited from Map.[iterator]
- Defined in node_modules/typescript/lib/lib.es2015.iterable.d.ts:141

clear

clear(): void
Removes all elements from the Map.

Returns void
Inherited from Map.clear
- Defined in node_modules/typescript/lib/lib.es2015.collection.d.ts:21

delete

delete(key: K): boolean
Parameters
- key: K
Returns boolean
true if an element in the Map existed and has been removed, or false if the element does not exist.
Inherited from Map.delete
- Defined in node_modules/typescript/lib/lib.es2015.collection.d.ts:25

entries

entries(): MapIterator<[K, V]>
Returns an iterable of key, value pairs for every entry in the map.

Returns MapIterator<[K, V]>
Inherited from Map.entries
- Defined in node_modules/typescript/lib/lib.es2015.iterable.d.ts:146

forEach

forEach(
callbackfn: (value: V, key: K, map: Map<K, V>) => void,
thisArg?: any,
): void
Executes a provided function once per each key/value pair in the Map, in insertion order.
Parameters
- callbackfn: (value: V, key: K, map: Map<K, V>) => void
- OptionalthisArg: any
Returns void
Inherited from Map.forEach
- Defined in node_modules/typescript/lib/lib.es2015.collection.d.ts:29

get

get(key: K): V | D
Get the value for a given key, or the default value if it's missing.

Time complexity: O(1)

Space complexity: O(1)
Parameters
- key: K
  The key to get the value for
Returns V | D
The value for key, or the default value if it's missing
Example
```
map.get('a');
```
Overrides Map.get
- Defined in src/map/default-map.ts:79

getOrInsert

getOrInsert(key: K, defaultValue: V): V
Returns a specified element from the Map object. If no element is associated with the specified key, a new element with the value defaultValue will be inserted into the Map and returned.
Parameters
- key: K
- defaultValue: V
Returns V
The element associated with the specified key, which will be defaultValue if no element previously existed.
Inherited from Map.getOrInsert
- Defined in node_modules/typescript/lib/lib.esnext.collection.d.ts:25

getOrInsertComputed

getOrInsertComputed(key: K, callback: (key: K) => V): V
Returns a specified element from the Map object. If no element is associated with the specified key, the result of passing the specified key to the callback function will be inserted into the Map and returned.
Parameters
- key: K
- callback: (key: K) => V
Returns V
The element associated with the specific key, which will be the newly computed value if no element previously existed.
Inherited from Map.getOrInsertComputed
- Defined in node_modules/typescript/lib/lib.esnext.collection.d.ts:31

has

has(key: K): boolean
Parameters
- key: K
Returns boolean
boolean indicating whether an element with the specified key exists or not.
Inherited from Map.has
- Defined in node_modules/typescript/lib/lib.es2015.collection.d.ts:38

keys

keys(): MapIterator<K>
Returns an iterable of keys in the map

Returns MapIterator<K>
Inherited from Map.keys
- Defined in node_modules/typescript/lib/lib.es2015.iterable.d.ts:151

set

set(key: K, value: V): this
Adds a new element with a specified key and value to the Map. If an element with the same key already exists, the element will be updated.
Parameters
- key: K
- value: V
Returns this
Inherited from Map.set
- Defined in node_modules/typescript/lib/lib.es2015.collection.d.ts:42

values

values(): MapIterator<V>
Returns an iterable of values in the map

Returns MapIterator<V>
Inherited from Map.values
- Defined in node_modules/typescript/lib/lib.es2015.iterable.d.ts:156

`Static`groupBy

groupBy<K, T>(
items: Iterable<T>,
keySelector: (item: T, index: number) => K,
): Map<K, T[]>
Groups members of an iterable according to the return value of the passed callback.
Type Parameters
- K
- T
Parameters
- items: Iterable<T>
  An iterable.
- keySelector: (item: T, index: number) => K
  A callback which will be invoked for each item in items.
Returns Map<K, T[]>
Inherited from Map.groupBy
- Defined in node_modules/typescript/lib/lib.es2024.collection.d.ts:23

Class DefaultMap<K, V, D>

Example

Example

Type Parameters

Hierarchy (View Summary)

Index

Constructors

Properties

Methods

Constructors

constructor

Type Parameters

Parameters

Returns DefaultMap<K, V, D>

Example

Type Parameters

Parameters

Returns DefaultMap<K, V, D>

Example

Properties

Readonly[toStringTag]

Readonlysize

Returns

Static Readonly[species]

Methods

[iterator]

Returns MapIterator<[K, V]>

clear

Returns void

delete

Parameters

Returns boolean

entries

Returns MapIterator<[K, V]>

forEach

Parameters

Returns void

get

Parameters

Returns V | D

Example

getOrInsert

Parameters

Returns V

getOrInsertComputed

Parameters

Returns V

has

Parameters

Returns boolean

keys

Returns MapIterator<K>

set

Parameters

Returns this

values

Returns MapIterator<V>

StaticgroupBy

Type Parameters

Parameters

Returns Map<K, T[]>

Settings

On This Page

`Readonly`[toStringTag]

`Readonly`size

`Static` `Readonly`[species]

`Static`groupBy