Collection.Set

Set Collections only represent values. They have no associated keys or indices. Duplicate values are possible in the lazy Seq.Sets, however the concrete Set Collection does not allow duplicate values.

type Collection.Set<T> extends Collection<T, T>

Collection methods on Collection.Set such as map and forEach will provide the value as both the first and second arguments to the provided function.

const seq = Collection.Set(['A', 'B', 'C']);
// Seq { "A", "B", "C" }
seq.forEach((v, k) => {
  assert.equal(v, k);
});

Construction

Similar to Collection(), but always returns a Collection.Set.

Collection.Set<T>(collection?: Iterable<T> | ArrayLike<T>): Collection.Set<T>

Note: Collection.Set is a factory function and not a class, and does not use the new keyword during construction.

Sequence algorithms

Returns a new Collection.Set with values passed through a mapper function.

map<M>(mapper: (value: T, key: T, iter: this) => M, context?: unknown): Collection.Set<M>

Note: map() always returns a new instance, even if it produced the same value at every step.

Flat-maps the Collection, returning a Collection of the same type.

Similar to collection.map(...).flatten(true).

flatMap<M>(mapper: (value: T, key: T, iter: this) => Iterable<M>, context?: unknown): Collection.Set<M>

Returns a new Collection with only the values for which the predicate function returns true.

Note: filter() always returns a new instance, even if it results in not filtering out any values.

filter(predicate: (value: T, key: T, iter: this) => boolean, context?: unknown): Collection.Set<T>

Returns a new Collection with only the values for which the predicate function returns false.

filterNot(predicate: (value: T, key: T, iter: this) => boolean, context?: unknown): Collection.Set<T>

Note: filterNot() always returns a new instance, even if it results in not filtering out any values.

Returns a new Collection with the values for which the predicate function returns false and another for which is returns true.

partition(predicate: (this: C, value: T, key: T, iter: this) => boolean, context?: C): [Collection.Set<T>, Collection.Set<T>]

Returns a Collection of the same type which includes the same entries, stably sorted by using a comparator.

sort(comparator?: Comparator<T>): this

If a comparator is not provided, a default comparator uses < and >.

comparator(valueA, valueB):

• Returns 0 if the elements should not be swapped.
• Returns -1 (or any negative number) if valueA comes before valueB
• Returns 1 (or any positive number) if valueA comes after valueB
• Alternatively, can return a value of the PairSorting enum type
• Is pure, i.e. it must always return the same value for the same pair of values.

When sorting collections which have no defined order, their ordered equivalents will be returned. e.g. map.sort() returns OrderedMap.

Note: sort() Always returns a new instance, even if the original was already sorted.

Note: This is always an eager operation.

Like sort, but also accepts a comparatorValueMapper which allows for sorting by more sophisticated means:

sortBy<C>(comparatorValueMapper: (value: T, key: T, iter: this) => C, comparator?: Comparator<C>): this

Note: sortBy() Always returns a new instance, even if the original was already sorted.

Note: This is always an eager operation.

Returns a new Set with the order of the values reversed.

reverse(): Set<T>

Returns a Map of Set, grouped by the return value of the grouper function.

groupBy<G>(grouper: (value: T, key: T, iter: this) => G, context?: unknown): Map<G, Set<T>>

Note: This is not a lazy operation.

Conversion to JavaScript types

Deeply converts this Set to equivalent native JavaScript Array.

toJS(): Array<DeepCopy<T>>

Shallowly converts this Set to equivalent native JavaScript Array.

toJSON(): Array<T>

Shallowly converts this collection to an Array.

toArray(): Array<T>

Shallowly converts this Collection to an Object.

toObject(): { [key: string]: T }

Converts keys to Strings.

Conversion to Seq

Returns itself.

toSeq(): Seq.Set<T>

Returns a Seq.Keyed from this Collection where indices are treated as keys.

This is useful if you want to operate on a Collection and preserve the [value, value] pairs.

toKeyedSeq(): Seq.Keyed<T, T>

Returns an Seq.Indexed of the values of this Collection, discarding keys.

toIndexedSeq(): Seq.Indexed<T>

Returns a Seq.Set of the values of this Collection, discarding keys.

toSetSeq(): Seq.Set<T>

Value equality

True if this and the other Collection have value equality, as defined by Immutable.is().

equals(other): boolean

Note: This is equivalent to Immutable.is(this, other), but provided to allow for chained expressions.

Computes and returns the hashed identity for this Collection.

The hashCode of a Collection is used to determine potential equality, and is used when adding this to a Set or as a key in a Map, enabling lookup via a different instance.

hashCode(): number

If two values have the same hashCode, they are not guaranteed to be equal. If two values have different hashCodes, they must not be equal.

Reading values

Returns the value associated with the provided key, or notSetValue if the Collection does not contain this key.

Note: it is possible a key may be associated with an undefined value, so if notSetValue is not provided and this method returns undefined, that does not guarantee the key was not found.

get<NSV>(key: T, notSetValue: NSV): T | NSV
get(key: T): T | undefined

True if a key exists within this Collection, using Immutable.is to determine equality.

has(key: T): boolean

True if a value exists within this Collection, using Immutable.is to determine equality.

includes(value: T): boolean

Returns the first value in this Collection.

first<NSV>(notSetValue: NSV): T | NSV
first(): T | undefined

Returns the last value in this Collection.

last<NSV>(notSetValue: NSV): T | NSV
last(): T | undefined

Reading deep values

Returns the value found by following a path of keys or indices through nested Collections.

getIn(searchKeyPath: Iterable<unknown>, notSetValue?: unknown): unknown

Plain JavaScript Object or Arrays may be nested within an Immutable.js Collection, and getIn() can access those values as well:

True if the result of following a path of keys or indices through nested Collections results in a set value.

hasIn(searchKeyPath: Iterable<unknown>): boolean

Persistent changes

This can be very useful as a way to "chain" a normal function into a sequence of methods. RxJS calls this "let" and lodash calls it "thru".

update<R>(updater: (value: this) => R): R

For example, to sum a Seq after mapping and filtering:

Conversion to Collections

Converts this Collection to a Map, Throws if keys are not hashable.

toMap(): Map<T, T>

Note: This is equivalent to Map(this.toKeyedSeq()), but provided for convenience and to allow for chained expressions.

Converts this Collection to a Map, maintaining the order of iteration.

toOrderedMap(): OrderedMap<T, T>

Note: This is equivalent to OrderedMap(this.toKeyedSeq()), but provided for convenience and to allow for chained expressions.

Returns itself.

toSet(): Set<T>

Converts this Collection to a Set, maintaining the order of iteration.

toOrderedSet(): OrderedSet<T>

Note: This is equivalent to OrderedSet(this), but provided for convenience and to allow for chained expressions.

Converts this Collection to a List.

toList(): List<T>

Converts this Collection to a Stack, discarding keys. Throws if values are not hashable.

toStack(): Stack<T>

Note: This is equivalent to Stack(this), but provided to allow for chained expressions.

Iterators

An iterator of this Set's keys.

keys(): IterableIterator<T>

Note: this will return an ES6 iterator which does not support Immutable.js sequence algorithms. Use keySeq instead, if this is what you want.

An iterator of this Set's values.

values(): IterableIterator<T>

Note: this will return an ES6 iterator which does not support Immutable.js sequence algorithms. Use valueSeq instead, if this is what you want.

An iterator of this Set's entries as [value, value] tuples.

entries(): IterableIterator<[T, T]>

Note: this will return an ES6 iterator which does not support Immutable.js sequence algorithms. Use entrySeq instead, if this is what you want.

Collections (Seq)

Returns a new Seq.Indexed of the keys of this Collection, discarding values.

keySeq(): Seq.Indexed<T>

Returns an Seq.Indexed of the values of this Collection, discarding keys.

valueSeq(): Seq.Indexed<T>

Returns a new Seq.Indexed of [value, value] tuples.

entrySeq(): Seq.Indexed<[T, T]>

Side effects

The sideEffect is executed for every entry in the Collection.

forEach(sideEffect: (value: T, key: T, iter: this) => unknown, context?: unknown): number

Unlike Array#forEach, if any call of sideEffect returns false, the iteration will stop. Returns the number of entries iterated (including the last iteration which returned false).

Creating subsets

Returns a new Set of the same type representing a portion of this Set from start up to but not including end.

slice(begin?: number, end?: number): Set<T>

If begin is negative, it is offset from the end of the Collection. e.g. slice(-2) returns a Collection of the last two entries. If it is not provided the new Collection will begin at the beginning of this Collection.

If end is negative, it is offset from the end of the Collection. e.g. slice(0, -1) returns a Collection of everything but the last entry. If it is not provided, the new Collection will continue through the end of this Collection.

If the requested slice is equivalent to the current Collection, then it will return itself.

Returns a new Collection of the same type containing all entries except the first.

rest(): Set<T>

Returns a new Collection of the same type containing all entries except the last.

butLast(): Set<T>

Returns a new Collection of the same type which excludes the first amount entries from this Collection.

skip(amount: number): Set<T>

Returns a new Collection of the same type which excludes the last amount entries from this Collection.

skipLast(amount: number): Set<T>

Returns a new Collection of the same type which includes entries starting from when predicate first returns false.

skipWhile(predicate: (value: T, key: T, iter: this) => boolean, context?: unknown): Set<T>

Returns a new Collection of the same type which includes entries starting from when predicate first returns true.

skipUntil(predicate: (value: T, key: T, iter: this) => boolean, context?: unknown): Set<T>

Returns a new Collection of the same type which includes the first amount entries from this Collection.

take(amount: number): Set<T>

Returns a new Collection of the same type which includes the last amount entries from this Collection.

takeLast(amount: number): Set<T>

Returns a new Collection of the same type which includes entries from this Collection as long as the predicate returns true.

takeWhile(predicate: (value: T, key: T, iter: this) => boolean, context?: unknown): Set<T>

Returns a new Collection of the same type which includes entries from this Collection as long as the predicate returns false.

takeUntil(predicate: (value: T, key: T, iter: this) => boolean, context?: unknown): Set<T>

Combination

Returns a new Set with other collections concatenated to this one.

concat<C>(...valuesOrCollections: Array<Iterable<C> | C>): Set<T | C>

Flattens nested Collections.

Will deeply flatten the Collection by default, returning a Collection of the same type, but a depth can be provided in the form of a number or boolean (where true means to shallowly flatten one level). A depth of 0 (or shallow: false) will deeply flatten.

Flattens only others Collection, not Arrays or Objects.

flatten(depth?: number): this
flatten(shallow?: boolean): this

Flat-maps the Set, returning a new Set.

Similar to set.map(...).flatten(true).

flatMap<M>(mapper: (value: T, key: T, iter: this) => Iterable<M>, context?: unknown): Set<M>

Reducing a value

Reduces the Iterable to a value by calling the reducer for every entry in the Iterable and passing along the reduced value.

reduce<R>(reducer: (reduced: R, value: T, key: T, iter: this) => R, initialValue: R): R

If initialValue is not provided, the first entry in the Iterable will be used as the initial value.

Reduces the Iterable to a value by calling the reducer for every entry in the Iterable and passing along the reduced value.

reduceRight<R>(reducer: (reduced: R, value: T, key: T, iter: this) => R, initialValue: R): R

Note: Similar to this.reverse().reduce(), and provided for parity with Array#reduceRight.

Returns true if the predicate returns true for every entry in the Iterable.

every(predicate: (value: T, key: T, iter: this) => boolean, context?: unknown): boolean

Returns true if the predicate returns true for any entry in the Iterable.

some(predicate: (value: T, key: T, iter: this) => boolean, context?: unknown): boolean

Returns a string of all the entries in the Iterable, separated by separator.

join(separator?: string): string

Returns true if the Iterable is empty.

isEmpty(): boolean

Returns the number of entries in the Iterable.

count(): number

Returns a Map of the number of occurrences of each value in the Iterable.

countBy<G>(grouper: (value: T, key: T, iter: this) => G, context?: unknown): Map<G, number>

Search for value

Returns the first value for which the predicate returns true.

find(predicate: (value: T, key: T, iter: this) => boolean, context?: unknown, notSetValue?: T): T | undefined

Returns the last value for which the predicate returns true.

findLast(predicate: (value: T, key: T, iter: this) => boolean, context?: unknown, notSetValue?: T): T | undefined

Note: predicate will be called for each entry in reverse.

Returns the first [value, value] entry for which the predicate returns true.

findEntry(predicate: (value: T, key: T, iter: this) => boolean, context?: unknown, notSetValue?: T): [T, T] | undefined

Returns the last [value, value] entry for which the predicate returns true.

findLastEntry(predicate: (value: T, key: T, iter: this) => boolean, context?: unknown, notSetValue?: T): [T, T] | undefined

Note: predicate will be called for each entry in reverse.

Returns the first key for which the predicate returns true.

findKey(predicate: (value: T, key: T, iter: this) => boolean, context?: unknown): T | undefined

Returns the last key for which the predicate returns true.

findLastKey(predicate: (value: T, key: T, iter: this) => boolean, context?: unknown): T | undefined

Note: predicate will be called for each entry in reverse.

Returns the key associated with the search value, or undefined.

keyOf(searchValue: T): T | undefined

Returns the last key associated with the search value, or undefined.

lastKeyOf(searchValue: T): T | undefined

Returns the maximum value in this collection. If any values are comparatively equivalent, the first one found will be returned.

max(comparator?: Comparator<T>): T | undefined

The comparator is used in the same way as Collection#sort. If it is not provided, the default comparator is >.

When two values are considered equivalent, the first encountered will be returned. Otherwise, max will operate independent of the order of input as long as the comparator is commutative. The default comparator > is commutative only when types do not differ.

If comparator returns 0 and either value is NaN, undefined, or null, that value will be returned.

Like max, but also accepts a comparatorValueMapper which allows for comparing by more sophisticated means:

maxBy<C>(comparatorValueMapper: (value: T, key: T, iter: this) => C, comparator?: Comparator<C>): T | undefined

Returns the minimum value in this collection. If any values are comparatively equivalent, the first one found will be returned.

min(comparator?: Comparator<T>): T | undefined

The comparator is used in the same way as Collection#sort. If it is not provided, the default comparator is <.

When two values are considered equivalent, the first encountered will be returned. Otherwise, min will operate independent of the order of input as long as the comparator is commutative. The default comparator < is commutative only when types do not differ.

If comparator returns 0 and either value is NaN, undefined, or null, that value will be returned.

Like min, but also accepts a comparatorValueMapper which allows for comparing by more sophisticated means:

minBy<C>(comparatorValueMapper: (value: T, key: T, iter: this) => C, comparator?: Comparator<C>): T | undefined

Comparison

True if iter includes every value in this Collection.

isSubset(iter: Iterable<T>): boolean

True if this Collection includes every value in iter.

isSuperset(iter: Iterable<T>): boolean