Class DefaultMap<K, V, D>Category

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 full)

Constructors

constructor

Properties

[toStringTag] size [species]

Methods

[iterator] clear delete entries forEach get has keys set values

Constructors

constructor

  • new DefaultMap<K, V, D>(defaultValue, entries?): 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: null | Iterable<readonly [unknown, unknown]>

    Returns DefaultMap<K, V, D>

    Example

    const map = new DefaultMap(0);
  • new DefaultMap<K, V, D>(defaultValueFn, entries?): 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

    • defaultValueFn: ((key: K) => D)

      The function to generate default values

        • (key): D

        • Parameters

          • key: K

          Returns D

    • Optionalentries: null | Iterable<readonly [unknown, unknown]>

    Returns DefaultMap<K, V, D>

    Example

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

Properties

Readonly[toStringTag]

[toStringTag]: string

Readonlysize

size: number

Returns

the number of elements in the Map.

Static Readonly[species]

[species]: MapConstructor

Methods

[iterator]

  • [iterator](): IterableIterator<[K, V]>

  • Returns an iterable of entries in the map.

    Returns IterableIterator<[K, V]>

clear

  • clear(): void

  • Returns void

delete

  • delete(key): 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.

entries

  • entries(): IterableIterator<[K, V]>

  • Returns an iterable of key, value pairs for every entry in the map.

    Returns IterableIterator<[K, V]>

forEach

  • forEach(callbackfn, thisArg?): 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)
        • (value, key, map): void

        • Parameters

          • value: V
          • key: K
          • map: Map<K, V>

          Returns void

    • OptionalthisArg: any

    Returns void

get

  • get(key): 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');

has

  • has(key): boolean

  • Parameters

    • key: K

    Returns boolean

    boolean indicating whether an element with the specified key exists or not.

keys

  • keys(): IterableIterator<K>

  • Returns an iterable of keys in the map

    Returns IterableIterator<K>

set

  • set(key, value): 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

values

  • values(): IterableIterator<V>

  • Returns an iterable of values in the map

    Returns IterableIterator<V>

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