class Collection

extends

Map<Key, Value>
export declare class Collection<Key, Value> extends Map<Key, Value>

A Map with additional utility methods. This is used throughout discord.js rather than Arrays for anything that has an ID, for significantly improved performance and ease-of-use.

Type Parameters

Key

The key type this collection holds

Value

The value type this collection holds

at(
index: number
) : Value | undefined

Identical to Array.at(). Returns the item at a given index, allowing for positive and negative integers. Negative integers count back from the last item in the collection.

clone() : Collection<Key, Value>

Creates an identical shallow copy of this collection.

Examples:
const newColl = someColl.clone();

static
combineEntries<

Key

Value

>(
entries: Iterable<[Key, Value]>
combine: (firstValue: Value, secondValue: Value, key: Key) => Value
) : Collection<Key, Value>

Creates a Collection from a list of entries.

Examples:
Collection.combineEntries([["a", 1], ["b", 2], ["a", 2]], (x, y) => x + y);
// returns Collection { "a" => 3, "b" => 2 }

concat(
...collections: ReadonlyCollection<Key, Value>[]
) : Collection<Key, Value>

Combines this collection with others into a new collection. None of the source collections are modified.

Examples:
const newColl = someColl.concat(someOtherColl, anotherColl, ohBoyAColl);

difference(
other: ReadonlyCollection<Key, any>
) : Collection<Key, Value>

Returns a new collection containing the items where the key is present in this collection but not the other.

Examples:
const col1 = new Collection([['a', 1], ['b', 2]]);
const col2 = new Collection([['a', 1], ['c', 3]]);
console.log(col1.difference(col2));
// => Collection { 'b' => 2 }
console.log(col2.difference(col1));
// => Collection { 'c' => 3 }

each(
fn: (value: Value, key: Key, collection: this) => void
) : this

Identical to Map.forEach(), but returns the collection instead of undefined.

Examples:
collection
 .each(user => console.log(user.username))
 .filter(user => user.bot)
 .each(user => console.log(user.username));

ensure(
key: Key
defaultValueGenerator: (key: Key, collection: this) => Value
) : Value

Obtains the value of the given key if it exists, otherwise sets and returns the value provided by the default value generator.

Examples:
collection.ensure(guildId, () => defaultGuildConfig);

equals(
collection: ReadonlyCollection<Key, Value>
) : boolean

Checks if this collection shares identical items with another. This is different to checking for equality using equal-signs, because the collections may be different objects, but contain the same data.

Returns: Whether the collections have identical contents

every<

NewKey extends Key

>(
fn: (value: Value, key: Key, collection: this) => key is NewKey
) : this is Collection<NewKey, Value>

Checks if all items passes a test. Identical in behavior to Array.every().

Examples:
collection.every(user => !user.bot);

filter<

NewKey extends Key

>(
fn: (value: Value, key: Key, collection: this) => key is NewKey
) : Collection<NewKey, Value>

Identical to Array.filter(), but returns a Collection instead of an Array.

Examples:
collection.filter(user => user.username === 'Bob');

find<

NewValue extends Value

>(
fn: (value: Value, key: Key, collection: this) => value is NewValue
) : NewValue | undefined

Searches for a single item where the given function returns a truthy value. This behaves like Array.find(). All collections used in Discord.js are mapped using their id property, and if you want to find by id you should use the get method. See MDN for details.

Examples:
collection.find(user => user.username === 'Bob');

findKey<

NewKey extends Key

>(
fn: (value: Value, key: Key, collection: this) => key is NewKey
) : NewKey | undefined

Searches for the key of a single item where the given function returns a truthy value. This behaves like Array.findIndex(), but returns the key rather than the positional index.

Examples:
collection.findKey(user => user.username === 'Bob');

findLast<

NewValue extends Value

>(
fn: (value: Value, key: Key, collection: this) => value is NewValue
) : NewValue | undefined

Searches for a last item where the given function returns a truthy value. This behaves like Array.findLast().

findLastKey<

NewKey extends Key

>(
fn: (value: Value, key: Key, collection: this) => key is NewKey
) : NewKey | undefined

Searches for the key of a last item where the given function returns a truthy value. This behaves like Array.findLastIndex(), but returns the key rather than the positional index.

first() : Value | undefined

Obtains the first value(s) in this collection.

Returns: A single value if no amount is provided or an array of values, starting from the end if amount is negative

firstKey() : Key | undefined

Obtains the first key(s) in this collection.

Returns: A single key if no amount is provided or an array of keys, starting from the end if amount is negative

flatMap<

NewValue

>(
fn: (value: Value, key: Key, collection: this) => Collection<Key, NewValue>
) : Collection<Key, NewValue>

Maps each item into a Collection, then joins the results into a single Collection. Identical in behavior to Array.flatMap().

Examples:
collection.flatMap(guild => guild.members.cache);

hasAll(
...keys: Key[]
) : boolean

Checks if all of the elements exist in the collection.

Returns: true if all of the elements exist, false if at least one does not exist.

hasAny(
...keys: Key[]
) : boolean

Checks if any of the elements exist in the collection.

Returns: true if any of the elements exist, false if none exist.

intersection(
other: ReadonlyCollection<Key, any>
) : Collection<Key, Value>

The intersection method returns a new collection containing the items where the key is present in both collections.

Examples:
const col1 = new Collection([['a', 1], ['b', 2]]);
const col2 = new Collection([['a', 1], ['c', 3]]);
const intersection = col1.intersection(col2);
console.log(col1.intersection(col2));
// => Collection { 'a' => 1 }

keyAt(
index: number
) : Key | undefined

Identical to Array.at(). Returns the key at a given index, allowing for positive and negative integers. Negative integers count back from the last item in the collection.

last() : Value | undefined

Obtains the last value(s) in this collection.

Returns: A single value if no amount is provided or an array of values, starting from the start if amount is negative

lastKey() : Key | undefined

Obtains the last key(s) in this collection.

Returns: A single key if no amount is provided or an array of keys, starting from the start if amount is negative

map<

NewValue

>(
fn: (value: Value, key: Key, collection: this) => NewValue
) : NewValue[]

Maps each item to another value into an array. Identical in behavior to Array.map().

Examples:
collection.map(user => user.tag);

mapValues<

NewValue

>(
fn: (value: Value, key: Key, collection: this) => NewValue
) : Collection<Key, NewValue>

Maps each item to another value into a collection. Identical in behavior to Array.map().

Examples:
collection.mapValues(user => user.tag);

merge<

OtherValue

ResultValue

>(
other: ReadonlyCollection<Key, OtherValue>
whenInSelf: (value: Value, key: Key) => Keep<ResultValue>
whenInOther: (valueOther: OtherValue, key: Key) => Keep<ResultValue>
whenInBoth: (value: Value, valueOther: OtherValue, key: Key) => Keep<ResultValue>
) : Collection<Key, ResultValue>

Merges two Collections together into a new Collection.

Examples:
// Sums up the entries in two collections.
coll.merge(
 other,
 x => ({ keep: true, value: x }),
 y => ({ keep: true, value: y }),
 (x, y) => ({ keep: true, value: x + y }),
);
// Intersects two collections in a left-biased manner.
coll.merge(
 other,
 x => ({ keep: false }),
 y => ({ keep: false }),
 (x, _) => ({ keep: true, value: x }),
);

partition<

NewKey extends Key

>(
fn: (value: Value, key: Key, collection: this) => key is NewKey
) : [Collection<NewKey, Value>, Collection<Exclude<Key, NewKey>, Value>]

Partitions the collection into two collections where the first collection contains the items that passed and the second contains the items that failed.

Examples:
const [big, small] = collection.partition(guild => guild.memberCount > 250);

random() : Value | undefined

Obtains unique random value(s) from this collection.

Returns: A single value if no amount is provided or an array of values

randomKey() : Key | undefined

Obtains unique random key(s) from this collection.

Returns: A single key if no amount is provided or an array

reduce(
fn: (accumulator: Value, value: Value, key: Key, collection: this) => Value
initialValue?: Value
) : Value

Applies a function to produce a single value. Identical in behavior to Array.reduce().

Examples:
collection.reduce((acc, guild) => acc + guild.memberCount, 0);

reduceRight(
fn: (accumulator: Value, value: Value, key: Key, collection: this) => Value
initialValue?: Value
) : Value

Applies a function to produce a single value. Identical in behavior to Array.reduceRight().

reverse() : this

Identical to Array.reverse() but returns a Collection instead of an Array.

some(
fn: (value: Value, key: Key, collection: this) => unknown
) : boolean

Checks if there exists an item that passes a test. Identical in behavior to Array.some().

Examples:
collection.some(user => user.discriminator === '0000');

sort(
compareFunction?: Comparator<Key, Value>
) : this

The sort method sorts the items of a collection in place and returns it. The default sort order is according to string Unicode code points.

Examples:
collection.sort((userA, userB) => userA.createdTimestamp - userB.createdTimestamp);

sweep(
fn: (value: Value, key: Key, collection: this) => unknown
) : number

Removes items that satisfy the provided filter function.

Returns: The number of removed entries

symmetricDifference<

OtherValue

>(
other: ReadonlyCollection<Key, OtherValue>
) : Collection<Key, OtherValue | Value>

Returns a new collection containing only the items where the keys are present in either collection, but not both.

Examples:
const col1 = new Collection([['a', 1], ['b', 2]]);
const col2 = new Collection([['a', 1], ['c', 3]]);
const symmetricDifference = col1.symmetricDifference(col2);
console.log(col1.symmetricDifference(col2));
// => Collection { 'b' => 2, 'c' => 3 }

tap(
fn: (collection: this) => void
) : this

Runs a function on the collection and returns the collection.

Examples:
collection
 .tap(coll => console.log(coll.size))
 .filter(user => user.bot)
 .tap(coll => console.log(coll.size))

toJSON() : [Key, Value][]

toReversed() : Collection<Key, Value>

Identical to Array.toReversed() but returns a Collection instead of an Array.

toSorted(
compareFunction?: Comparator<Key, Value>
) : Collection<Key, Value>

The sorted method sorts the items of a collection and returns it. The default sort order is according to string Unicode code points.

Examples:
collection.sorted((userA, userB) => userA.createdTimestamp - userB.createdTimestamp);

union<

OtherValue

>(
other: ReadonlyCollection<Key, OtherValue>
) : Collection<Key, OtherValue | Value>

Returns a new collection containing the items where the key is present in either of the collections.

Examples:
const col1 = new Collection([['a', 1], ['b', 2]]);
const col2 = new Collection([['a', 1], ['b', 3], ['c', 3]]);
const union = col1.union(col2);
console.log(union);
// => Collection { 'a' => 1, 'b' => 2, 'c' => 3 }