ReversibleKeyMap

A Map extended call with support of two keys instead of one, the support of O(1) access to data linked to one of the two keys, with a non-relevant key order.

One ReversibleKeyMap object takes two keys in argument when setting a value. Keys are reversible: Order of the two keys is not relevant. You can also access data stored under one key (in the form of a map storing a key => value data) in a constant time.

This documentation will use TypeScript typing. Remove any type to restore "pure" JavaScript.

Getting started

// With a standard Map
const classic_map = new Map<string, string>();
classic_map.set('classic', 'map');
 
// <type_key1, type_key2, type_value>
const reversible_map = new ReversibleKeyMap<string, number, string[]>();
reversible_map.set('one', 2, ['value', 'other']);
 
// Key order is not important
reversible_map.set(3, 'four', ['my_values', 'in_this_array']);
 
reversible_map.get(3, 'four'); // => ['my_values', 'in_this_array']
reversible_map.get('four', 3); // => ['my_values', 'in_this_array']
reversible_map.get(2, 'one'); // => ['value', 'other']

Keys can be of any type (like in the Map object).

const other_map = new ReversibleKeyMap<HTMLElement, HTMLElement, Function>();
other_map.set(document.getElementById('hello'), document.getElementById('other-click'), myEventListener);

The number of keys allowed is unlimited and their order is not relevant.

To install the package, use:

$ npm install reversible-key-map

Usage

Main method are get, set, getAllFrom, has and hasCouple.

Instanciation

import ReversibleKeyMap from 'reversible-key-map';
 
const map = new ReversibleKeyMap<string, string, number>();
// You can instanciate with an entries array
const from_it = new ReversibleKeyMap([ [['Hello', 'world'], 3], [['Second', 'value'], 5] ]);

Set values

map.set("one", "two", 3);
map.set("four", "one", 5);
map.set("six", "seven", 8);
// Setters are chainable
map.set("nine", "ten", 11).set("twelve", "thirteen", 14);

Get values

map.get("two", "one"); // => 3
map.get("four", "one"); // => 5
map.get("six", "one"); // => undefined
// You can all values linked to one key
map.getAllFrom("one"); // => Map(2) {"two" => 3, "four" => 5}

Iteration

Iteration through .entries(), Symbol.iterator, .values(), .keysCouple() ensure that getting a value with those methods will not give you duplicates.

With .keys(), a call to .getAllFrom(key) within the loop will give you the same value twice.

/// Iterate through the map
const entries = Array.from(map.entries() /* map.entries() is a generator */);
// Using Symbol.iterator | .entries()
for (const [keys, value] of map) {
    // ["one", "two"], 3
    // ["one", "four"], 5
    // ["six", "seven"], 8
    // ["nine", "ten"], 11
    // ["twelve", "thirteen"], 14
}
 
// Iterate through values only
for (const value of map.values()) {
    // 3
    // 5
    // 8
    // 11
    // 14
}
 
// Iterate through keys couples only
for (const keys of map.keysCouples()) {
    // ["one", "two"]
    // ["one", "four"]
    // ["six", "seven"]
    // ["nine", "ten"]
    // ["twelve", "thirteen"]
    const value = map.get(...keys);
    // use value or keys...
}
 
// Iterate through keys
for (const key of map.keys()) {
    // one
    // two
    // four
    // six
    // seven
    // nine
    // ten
    // twelve
    // thirteen
    const linked_maps = map.getAllFrom(key);
}

Appartenance

map.hasCouple("one", "two"); // => true
map.hasCouple("six", "one"); // => false
// Test if one key exists
map.has("one"); // => true
map.has("hello"); // => false

Delete values

/// Delete values
map.delete("one", "two"); // Deletions are also chainable.
// Delete all values linked to one key
map.deleteAllFrom("one");
 
console.log(...map); // [["six", "seven"], 8]  [["nine", "ten"], 11]  [["twelve", "thirteen"], 14]

Full reference: ReversibleKeyMap

Map using a couple of keys to reference a value. You can get a map of values using ONE key, and a value using TWO keys.

Key order is not important.

Index

Constructors

• constructor

Properties

• map

Accessors

• __@toStringTag
• count
• size

Methods

• __@iterator
• clear
• delete
• deleteAllFrom
• entries
• forEach
• get
• getAllFrom
• has
• hasCouple
• keys
• keysCouples
• set
• values

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Constructors

constructor

⊕ new ReversibleKeyMap(it?: Iterable<[[K1, K2], T]>): ReversibleKeyMap

⊕ new ReversibleKeyMap(it?: Iterable<[[K2, K1], T]>): ReversibleKeyMap

Creates an instance of ReversibleKeyMap. You can give an iterable providing a tuple containaing a tuple of two keys and one value to initialize the instance.

Parameters:

Name	Type
Optional it	Iterable<[[K1, K2], T]>

Returns: ReversibleKeyMap

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Properties

<Protected> map

● map: Map<K1 | K2, Map<K1 | K2, T>> = new Map

---

Accessors

__@toStringTag

get __@toStringTag(): string

Returns: string

---

count

get count(): number

Get map size using the VALUES. Warning, it have O(n) complexity.

readonly:

Returns: number

---

size

get size(): number

Get map size using the KEYS. Warning, it count EVERY key. It means that one set("a", "b", val) will produce a result of 2. 0(1) complexity.

readonly:

Returns: number

---

Methods

__@iterator

▸ __@iterator(): IterableIterator<[[K1 | K2, K1 | K2], T]>

Returns: IterableIterator<[[K1 | K2, K1 | K2], T]>

---

clear

▸ clear(): void

Delete all existing values in current instance.

Returns: void

---

delete

▸ delete(k1: K1, k2: K2): this

▸ delete(k1: K2, k2: K1): this

Delete a double key pair.

Parameters:

Name	Type	Description
k1	K1	-
k2	K2	-

Returns: this

---

deleteAllFrom

▸ deleteAllFrom(k1: K1 | K2): this

Delete everythinh linked to key k1.

Parameters:

Name	Type	Description
k1	K1 | K2	-

Returns: this

---

entries

▸ entries(): IterableIterator<[[K1 | K2, K1 | K2], T]>

Returns: IterableIterator<[[K1 | K2, K1 | K2], T]>

---

forEach

▸ forEach<This>(callback: function, thisArg?: This): void

Apply function callback for each [key1, key2] => value pair in ReversibleKeyMap object. Insertion order / key order is not guaranteed. If thisArg is provided, it will be used as this value for each callback call.

template: This

Type parameters:

This

Parameters:

Name	Type	Description
callback	function	-
Optional thisArg	This

Returns: void

---

get

▸ get(k1: K1, k2: K2): T

▸ get(k1: K2, k2: K1): T

Get one value according to a couple of keys. Order of keys does NOT have any influence.

Parameters:

Name	Type	Description
k1	K1	-
k2	K2

Returns: T

---

getAllFrom

▸ getAllFrom(k1: K1): Map<K2, T>

▸ getAllFrom(k1: K2): Map<K1, T>

Give all keys and values mapped to k1. Results are returned wrapped into a Map object.

Parameters:

Name	Type	Description
k1	K1	-

Returns: Map<K2, T>

---

has

▸ has(k1: K1 | K2): boolean

Return true if key k1 is present.

Parameters:

Name	Type	Description
k1	K1 | K2	-

Returns: boolean

---

hasCouple

▸ hasCouple(k1: K1, k2: K2): boolean

▸ hasCouple(k1: K2, k2: K1): boolean

Return true if couple [k1, k2] is present.

Parameters:

Name	Type	Description
k1	K1	-
k2	K2	-

Returns: boolean

---

keys

▸ keys(): IterableIterator<K1 | K2>

Get all keys existing in double key map. Do NOT return key couples, see keysCouples method.

Returns: IterableIterator<K1 | K2>

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keysCouples

▸ keysCouples(): IterableIterator<[K1 | K2, K1 | K2]>

Get existing key couples in double key maps.

Returns: IterableIterator<[K1 | K2, K1 | K2]>

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set

▸ set(k1: K1, k2: K2, value: T): this

▸ set(k1: K2, k2: K1, value: T): this

Set one value according to two keys.

Parameters:

Name	Type	Description
k1	K1	-
k2	K2	-
value	T	-

Returns: this Current instance.

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values

▸ values(): IterableIterator<T>

Get each value inside map.

Returns: IterableIterator<T>

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