List

Lists are ordered indexed dense collections, much like a JavaScript Array.

type List<T> extends Collection.Indexed<T>

Discussion

Lists are immutable and fully persistent with O(log32 N) gets and sets, and O(1) push and pop.

Lists implement Deque, with efficient addition and removal from both the end (push, pop) and beginning (unshift, shift).

Unlike a JavaScript Array, there is no distinction between an "unset" index and an index set to undefined. List#forEach visits all indices from 0 to size, regardless of whether they were explicitly defined.

Construction

List()

Create a new immutable List containing the values of the provided collection-like.

List<T>(collection?: Iterable<T> | ArrayLike<T>): List<T>

Discussion

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

const { List, Set } = require('immutable')

const emptyList = List()
// List []

const plainArray = [ 1, 2, 3, 4 ]
const listFromPlainArray = List(plainArray)
// List [ 1, 2, 3, 4 ]

const plainSet = Set([ 1, 2, 3, 4 ])
const listFromPlainSet = List(plainSet)
// List [ 1, 2, 3, 4 ]

const arrayIterator = plainArray[Symbol.iterator]()
const listFromCollectionArray = List(arrayIterator)
// List [ 1, 2, 3, 4 ]

listFromPlainArray.equals(listFromCollectionArray) // true
listFromPlainSet.equals(listFromCollectionArray) // true
listFromPlainSet.equals(listFromPlainArray) // truerun it

Static methods

List.isList()

List.isList(maybeList: unknown): boolean

List.of()

List.of<T>(...values: Array<T>): List<T>

Members

size

The number of items in this List.

size: number

Persistent changes

set()

Returns a new List which includes value at index. If index already exists in this List, it will be replaced.

set(index: number, value: T): List<T>

Discussion

index may be a negative number, which indexes back from the end of the List. v.set(-1, "value") sets the last item in the List.

If index larger than size, the returned List's size will be large enough to include the index.

const originalList = List([ 0 ]);
// List [ 0 ]
originalList.set(1, 1);
// List [ 0, 1 ]
originalList.set(0, 'overwritten');
// List [ "overwritten" ]
originalList.set(2, 2);
// List [ 0, undefined, 2 ]

List().set(50000, 'value').size;
// 50001run it

Note: set can be used in withMutations.

delete()

Returns a new List which excludes this index and with a size 1 less than this List. Values at indices above index are shifted down by 1 to fill the position.

delete(index: number): List<T>

alias

remove()

Discussion

This is synonymous with list.splice(index, 1).

index may be a negative number, which indexes back from the end of the List. v.delete(-1) deletes the last item in the List.

Note: delete cannot be safely used in IE8

List([ 0, 1, 2, 3, 4 ]).delete(0);
// List [ 1, 2, 3, 4 ]run it

Since delete() re-indexes values, it produces a complete copy, which has O(N) complexity.

Note: delete cannot be used in withMutations.

insert()

Returns a new List with value at index with a size 1 more than this List. Values at indices above index are shifted over by 1.

insert(index: number, value: T): List<T>

Discussion

This is synonymous with list.splice(index, 0, value).

List([ 0, 1, 2, 3, 4 ]).insert(6, 5)
// List [ 0, 1, 2, 3, 4, 5 ]run it

Since insert() re-indexes values, it produces a complete copy, which has O(N) complexity.

Note: insert cannot be used in withMutations.

clear()

Returns a new List with 0 size and no values in constant time.

clear(): List<T>

Discussion

List([ 1, 2, 3, 4 ]).clear()
// List []run it

Note: clear can be used in withMutations.

push()

Returns a new List with the provided values appended, starting at this List's size.

push(...values: Array<T>): List<T>

Discussion

List([ 1, 2, 3, 4 ]).push(5)
// List [ 1, 2, 3, 4, 5 ]run it

Note: push can be used in withMutations.

pop()

Returns a new List with a size ones less than this List, excluding the last index in this List.

pop(): List<T>

Discussion

Note: this differs from Array#pop because it returns a new List rather than the removed value. Use last() to get the last value in this List.

List([ 1, 2, 3, 4 ]).pop()
// List[ 1, 2, 3 ]

Note: pop can be used in withMutations.

unshift()

Returns a new List with the provided values prepended, shifting other values ahead to higher indices.

unshift(...values: Array<T>): List<T>

Discussion

List([ 2, 3, 4]).unshift(1);
// List [ 1, 2, 3, 4 ]run it

Note: unshift can be used in withMutations.

shift()

Returns a new List with a size ones less than this List, excluding the first index in this List, shifting all other values to a lower index.

shift(): List<T>

Discussion

Note: this differs from Array#shift because it returns a new List rather than the removed value. Use first() to get the first value in this List.

List([ 0, 1, 2, 3, 4 ]).shift();
// List [ 1, 2, 3, 4 ]run it

Note: shift can be used in withMutations.

update()

update(index: number, notSetValue: T, updater: (value: T) => T): this
update(index: number, updater: (value: T | undefined) => T | undefined): this
update<R>(updater: (value: this) => R): R

Overrides

Collection#update()

setSize()

Returns a new List with size size. If size is less than this List's size, the new List will exclude values at the higher indices. If size is greater than this List's size, the new List will have undefined values for the newly available indices.

setSize(size: number): List<T>

Discussion

When building a new List and the final size is known up front, setSize used in conjunction with withMutations may result in the more performant construction.

Deep persistent changes

setIn()

Returns a new List having set value at this keyPath. If any keys in keyPath do not exist, a new immutable Map will be created at that key.

setIn(keyPath: Iterable<unknown>, value: unknown): this

Discussion

Index numbers are used as keys to determine the path to follow in the List.

const { List } = require('immutable')
const list = List([ 0, 1, 2, List([ 3, 4 ])])
list.setIn([3, 0], 999);
// List [ 0, 1, 2, List [ 999, 4 ] ]run it

Plain JavaScript Object or Arrays may be nested within an Immutable.js Collection, and setIn() can update those values as well, treating them immutably by creating new copies of those values with the changes applied.

const { List } = require('immutable')
const list = List([ 0, 1, 2, { plain: 'object' }])
list.setIn([3, 'plain'], 'value');
// List([ 0, 1, 2, { plain: 'value' }])run it

Note: setIn can be used in withMutations.

deleteIn()

Returns a new List having removed the value at this keyPath. If any keys in keyPath do not exist, no change will occur.

deleteIn(keyPath: Iterable<unknown>): this

alias

removeIn()

Discussion

const { List } = require('immutable')
const list = List([ 0, 1, 2, List([ 3, 4 ])])
list.deleteIn([3, 0]);
// List [ 0, 1, 2, List [ 4 ] ]run it

Plain JavaScript Object or Arrays may be nested within an Immutable.js Collection, and removeIn() can update those values as well, treating them immutably by creating new copies of those values with the changes applied.

const { List } = require('immutable')
const list = List([ 0, 1, 2, { plain: 'object' }])
list.removeIn([3, 'plain']);
// List([ 0, 1, 2, {}])run it

Note: deleteIn cannot be safely used in withMutations.

updateIn()

updateIn(keyPath: Iterable<unknown>,
notSetValue: unknown,
updater: (value: unknown) => unknown
): this
updateIn(keyPath: Iterable<unknown>, updater: (value: unknown) => unknown): this

mergeIn()

Note: mergeIn can be used in withMutations.

mergeIn(keyPath: Iterable<unknown>, ...collections: Array<unknown>): this

see

Map#mergeIn

mergeDeepIn()

Note: mergeDeepIn can be used in withMutations.

mergeDeepIn(keyPath: Iterable<unknown>, ...collections: Array<unknown>): this

see

Map#mergeDeepIn

Transient changes

withMutations()

Note: Not all methods can be safely used on a mutable collection or within withMutations! Check the documentation for each method to see if it allows being used in withMutations.

withMutations(mutator: (mutable: this) => unknown): this

see

Map#withMutations

asMutable()

An alternative API for withMutations()

asMutable(): this

see

Map#asMutable

Discussion

Note: Not all methods can be safely used on a mutable collection or within withMutations! Check the documentation for each method to see if it allows being used in withMutations.

wasAltered()

wasAltered(): boolean

see

Map#wasAltered

asImmutable()

asImmutable(): this

see

Map#asImmutable

Sequence algorithms

concat()

Returns a new List with other values or collections concatenated to this one.

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

Overrides

Collection.Indexed#concat()

alias

merge()

Discussion

Note: concat can be used in withMutations.

map()

Returns a new List with values passed through a mapper function.

map<M>(mapper: (value: T, key: number, iter: this) => M,
context?: unknown
): List<M>

Overrides

Collection.Indexed#map()

Discussion

List([ 1, 2 ]).map(x => 10 * x)
// List [ 10, 20 ]run it

flatMap()

Flat-maps the List, returning a new List.

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

Overrides

Collection.Indexed#flatMap()

Discussion

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

filter()

filter<F>(predicate: (value: T, index: number, iter: this) => boolean,
context?: unknown
): List<F>
filter(predicate: (value: T, index: number, iter: this) => unknown,
context?: unknown
): this

Overrides

Collection.Indexed#filter()

partition()

partition<F, C>(predicate: (this: C, value: T, index: number, iter: this) => boolean,
context?: C
): [List<T>, List<F>]
partition<C>(predicate: (this: C, value: T, index: number, iter: this) => unknown,
context?: C
): [this, this]

Overrides

Collection.Indexed#partition()

zip()

zip<U>(other: Collection<unknown, U>): List<[T, U]>
zip<U, V>(other: Collection<unknown, U>,
other2: Collection<unknown, V>
): List<[T, U, V]>
zip(...collections: Array<Collection<unknown, unknown>>): List<unknown>

Overrides

Collection.Indexed#zip()

zipAll()

zipAll<U>(other: Collection<unknown, U>): List<[T, U]>
zipAll<U, V>(other: Collection<unknown, U>,
other2: Collection<unknown, V>
): List<[T, U, V]>
zipAll(...collections: Array<Collection<unknown, unknown>>): List<unknown>

Overrides

Collection.Indexed#zipAll()

zipWith()

zipWith<U, Z>(zipper: (value: T, otherValue: U) => Z,
otherCollection: Collection<unknown, U>
): List<Z>
zipWith<U, V, Z>(zipper: (value: T, otherValue: U, thirdValue: V) => Z,
otherCollection: Collection<unknown, U>,
thirdCollection: Collection<unknown, V>
): List<Z>
zipWith<Z>(zipper: (...values: Array<unknown>) => Z,
...collections: Array<Collection<unknown, unknown>>
): List<Z>

Overrides

Collection.Indexed#zipWith()

[Symbol.iterator]()

[Symbol.iterator](): IterableIterator<T>

Inherited from

Collection.Indexed#[Symbol.iterator]()

filterNot()

Returns a new Collection of the same type with only the entries for which the predicate function returns false.

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

Inherited from

Collection#filterNot()

Discussion

const { Map } = require('immutable') Map({ a: 1, b: 2, c: 3, d: 4}).filterNot(x => x % 2 === 0) // Map { "a": 1, "c": 3 }run it

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

reverse()

Returns a new Collection of the same type in reverse order.

reverse(): this

Inherited from

Collection#reverse()

sort()

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

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

Inherited from

Collection#sort()

Discussion

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.

const { Map } = require('immutable')
Map({ "c": 3, "a": 1, "b": 2 }).sort((a, b) => {
  if (a < b) { return -1; }
  if (a > b) { return 1; }
  if (a === b) { return 0; }
});
// OrderedMap { "a": 1, "b": 2, "c": 3 }run it

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

Note: This is always an eager operation.

sortBy()

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

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

Inherited from

Collection#sortBy()

Discussion

const { Map } = require('immutable') const beattles = Map({ John: { name: "Lennon" }, Paul: { name: "McCartney" }, George: { name: "Harrison" }, Ringo: { name: "Starr" }, }); beattles.sortBy(member => member.name);run it

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

Note: This is always an eager operation.

groupBy()

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

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

Inherited from

Collection#groupBy()

Discussion

Note: This is always an eager operation.

const { List, Map } = require('immutable')
const listOfMaps = List([
  Map({ v: 0 }),
  Map({ v: 1 }),
  Map({ v: 1 }),
  Map({ v: 0 }),
  Map({ v: 2 })
])
const groupsOfMaps = listOfMaps.groupBy(x => x.get('v'))
// Map {
//   0: List [ Map{ "v": 0 }, Map { "v": 0 } ],
//   1: List [ Map{ "v": 1 }, Map { "v": 1 } ],
//   2: List [ Map{ "v": 2 } ],
// }run it

Conversion to JavaScript types

toJS()

Deeply converts this Indexed collection to equivalent native JavaScript Array.

toJS(): Array<DeepCopy<T>>

Inherited from

Collection.Indexed#toJS()

toJSON()

Shallowly converts this Indexed collection to equivalent native JavaScript Array.

toJSON(): Array<T>

Inherited from

Collection.Indexed#toJSON()

toArray()

Shallowly converts this collection to an Array.

toArray(): Array<T>

Inherited from

Collection.Indexed#toArray()

toObject()

Shallowly converts this Collection to an Object.

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

Inherited from

Collection#toObject()

Discussion

Converts keys to Strings.

Reading values

get()

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

Inherited from

Collection.Indexed#get()

has()

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

has(key: number): boolean

Inherited from

Collection#has()

includes()

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

includes(value: T): boolean

Inherited from

Collection#includes()

alias

contains()

first()

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

Inherited from

Collection#first()

last()

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

Inherited from

Collection#last()

Conversion to Seq

toSeq()

Returns Seq.Indexed.

toSeq(): Seq.Indexed<T>

Inherited from

Collection.Indexed#toSeq()

fromEntrySeq()

If this is a collection of [key, value] entry tuples, it will return a Seq.Keyed of those entries.

fromEntrySeq(): Seq.Keyed<unknown, unknown>

Inherited from

Collection.Indexed#fromEntrySeq()

toKeyedSeq()

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

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

Inherited from

Collection#toKeyedSeq()

Discussion

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

The returned Seq will have identical iteration order as this Collection.

const { Seq } = require('immutable')
const indexedSeq = Seq([ 'A', 'B', 'C' ])
// Seq [ "A", "B", "C" ]
indexedSeq.filter(v => v === 'B')
// Seq [ "B" ]
const keyedSeq = indexedSeq.toKeyedSeq()
// Seq { 0: "A", 1: "B", 2: "C" }
keyedSeq.filter(v => v === 'B')
// Seq { 1: "B" }run it

toIndexedSeq()

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

toIndexedSeq(): Seq.Indexed<T>

Inherited from

Collection#toIndexedSeq()

toSetSeq()

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

toSetSeq(): Seq.Set<T>

Inherited from

Collection#toSetSeq()

Combination

interpose()

Returns a Collection of the same type with separator between each item in this Collection.

interpose(separator: T): this

Inherited from

Collection.Indexed#interpose()

interleave()

Returns a Collection of the same type with the provided collections interleaved into this collection.

interleave(...collections: Array<Collection<unknown, T>>): this

Inherited from

Collection.Indexed#interleave()

Discussion

The resulting Collection includes the first item from each, then the second from each, etc.

const { List } = require('immutable')
List([ 1, 2, 3 ]).interleave(List([ 'A', 'B', 'C' ]))
// List [ 1, "A", 2, "B", 3, "C" ]run it

The shortest Collection stops interleave.

List([ 1, 2, 3 ]).interleave(
  List([ 'A', 'B' ]),
  List([ 'X', 'Y', 'Z' ])
)
// List [ 1, "A", "X", 2, "B", "Y" ]run it

Since interleave() re-indexes values, it produces a complete copy, which has O(N) complexity.

Note: interleave cannot be used in withMutations.

splice()

Splice returns a new indexed Collection by replacing a region of this Collection with new values. If values are not provided, it only skips the region to be removed.

splice(index: number, removeNum: number, ...values: Array<T>): this

Inherited from

Collection.Indexed#splice()

Discussion

index may be a negative number, which indexes back from the end of the Collection. s.splice(-2) splices after the second to last item.

const { List } = require('immutable')
List([ 'a', 'b', 'c', 'd' ]).splice(1, 2, 'q', 'r', 's')
// List [ "a", "q", "r", "s", "d" ]run it

Since splice() re-indexes values, it produces a complete copy, which has O(N) complexity.

Note: splice cannot be used in withMutations.

flatten()

flatten(depth?: number): Collection<unknown, unknown>
flatten(shallow?: boolean): Collection<unknown, unknown>

Inherited from

Collection#flatten()

Search for value

indexOf()

Returns the first index at which a given value can be found in the Collection, or -1 if it is not present.

indexOf(searchValue: T): number

Inherited from

Collection.Indexed#indexOf()

lastIndexOf()

Returns the last index at which a given value can be found in the Collection, or -1 if it is not present.

lastIndexOf(searchValue: T): number

Inherited from

Collection.Indexed#lastIndexOf()

findIndex()

Returns the first index in the Collection where a value satisfies the provided predicate function. Otherwise -1 is returned.

findIndex(predicate: (value: T, index: number, iter: this) => boolean,
context?: unknown
): number

Inherited from

Collection.Indexed#findIndex()

findLastIndex()

Returns the last index in the Collection where a value satisfies the provided predicate function. Otherwise -1 is returned.

findLastIndex(predicate: (value: T, index: number, iter: this) => boolean,
context?: unknown
): number

Inherited from

Collection.Indexed#findLastIndex()

find()

Returns the first value for which the predicate returns true.

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

Inherited from

Collection#find()

findLast()

Returns the last value for which the predicate returns true.

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

Inherited from

Collection#findLast()

Discussion

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

findEntry()

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

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

Inherited from

Collection#findEntry()

findLastEntry()

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

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

Inherited from

Collection#findLastEntry()

Discussion

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

findKey()

Returns the key for which the predicate returns true.

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

Inherited from

Collection#findKey()

findLastKey()

Returns the last key for which the predicate returns true.

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

Inherited from

Collection#findLastKey()

Discussion

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

keyOf()

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

keyOf(searchValue: T): number | undefined

Inherited from

Collection#keyOf()

lastKeyOf()

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

lastKeyOf(searchValue: T): number | undefined

Inherited from

Collection#lastKeyOf()

max()

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

Inherited from

Collection#max()

Discussion

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.

maxBy()

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

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

Inherited from

Collection#maxBy()

Discussion

const { List, } = require('immutable'); const l = List([ { name: 'Bob', avgHit: 1 }, { name: 'Max', avgHit: 3 }, { name: 'Lili', avgHit: 2 } , ]); l.maxBy(i => i.avgHit); // will output { name: 'Max', avgHit: 3 }run it

min()

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

Inherited from

Collection#min()

Discussion

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.

minBy()

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

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

Inherited from

Collection#minBy()

Discussion

const { List, } = require('immutable'); const l = List([ { name: 'Bob', avgHit: 1 }, { name: 'Max', avgHit: 3 }, { name: 'Lili', avgHit: 2 } , ]); l.minBy(i => i.avgHit); // will output { name: 'Bob', avgHit: 1 }run it

Value equality

equals()

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

equals(other: unknown): boolean

Inherited from

Collection#equals()

Discussion

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

hashCode()

Computes and returns the hashed identity for this Collection.

hashCode(): number

Inherited from

Collection#hashCode()

Discussion

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.

const a = List([ 1, 2, 3 ]);
const b = List([ 1, 2, 3 ]);
assert.notStrictEqual(a, b); // different instances
const set = Set([ a ]);
assert.equal(set.has(b), true);run it

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 deep values

getIn()

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

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

Inherited from

Collection#getIn()

Discussion

const { Map, List } = require('immutable') const deepData = Map({ x: List([ Map({ y: 123 }) ]) }); deepData.getIn(['x', 0, 'y']) // 123run it

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

const { Map, List } = require('immutable') const deepData = Map({ x: [ { y: 123 } ] }); deepData.getIn(['x', 0, 'y']) // 123run it

hasIn()

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

Inherited from

Collection#hasIn()

Conversion to Collections

toMap()

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

toMap(): Map<number, T>

Inherited from

Collection#toMap()

Discussion

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

toOrderedMap()

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

toOrderedMap(): OrderedMap<number, T>

Inherited from

Collection#toOrderedMap()

Discussion

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

toSet()

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

toSet(): Set<T>

Inherited from

Collection#toSet()

Discussion

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

toOrderedSet()

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

toOrderedSet(): OrderedSet<T>

Inherited from

Collection#toOrderedSet()

Discussion

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

toList()

Converts this Collection to a List, discarding keys.

toList(): List<T>

Inherited from

Collection#toList()

Discussion

This is similar to List(collection), but provided to allow for chained expressions. However, when called on Map or other keyed collections, collection.toList() discards the keys and creates a list of only the values, whereas List(collection) creates a list of entry tuples.

const { Map, List } = require('immutable')
var myMap = Map({ a: 'Apple', b: 'Banana' })
List(myMap) // List [ [ "a", "Apple" ], [ "b", "Banana" ] ]
myMap.toList() // List [ "Apple", "Banana" ]run it

toStack()

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

toStack(): Stack<T>

Inherited from

Collection#toStack()

Discussion

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

Iterators

keys()

An iterator of this Collection's keys.

keys(): IterableIterator<number>

Inherited from

Collection#keys()

Discussion

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

values()

An iterator of this Collection's values.

values(): IterableIterator<T>

Inherited from

Collection#values()

Discussion

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

entries()

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

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

Inherited from

Collection#entries()

Discussion

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)

keySeq()

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

keySeq(): Seq.Indexed<number>

Inherited from

Collection#keySeq()

valueSeq()

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

valueSeq(): Seq.Indexed<T>

Inherited from

Collection#valueSeq()

entrySeq()

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

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

Inherited from

Collection#entrySeq()

Side effects

forEach()

The sideEffect is executed for every entry in the Collection.

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

Inherited from

Collection#forEach()

Discussion

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

slice()

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

slice(begin?: number, end?: number): this

Inherited from

Collection#slice()

Discussion

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.

rest()

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

rest(): this

Inherited from

Collection#rest()

butLast()

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

butLast(): this

Inherited from

Collection#butLast()

skip()

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

skip(amount: number): this

Inherited from

Collection#skip()

skipLast()

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

skipLast(amount: number): this

Inherited from

Collection#skipLast()

skipWhile()

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

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

Inherited from

Collection#skipWhile()

Discussion

const { List } = require('immutable') List([ 'dog', 'frog', 'cat', 'hat', 'god' ]) .skipWhile(x => x.match(/g/)) // List [ "cat", "hat", "god" ]run it

skipUntil()

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

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

Inherited from

Collection#skipUntil()

Discussion

const { List } = require('immutable') List([ 'dog', 'frog', 'cat', 'hat', 'god' ]) .skipUntil(x => x.match(/hat/)) // List [ "hat", "god" ]run it

take()

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

take(amount: number): this

Inherited from

Collection#take()

takeLast()

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

takeLast(amount: number): this

Inherited from

Collection#takeLast()

takeWhile()

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: number, iter: this) => boolean,
context?: unknown
): this

Inherited from

Collection#takeWhile()

Discussion

const { List } = require('immutable') List([ 'dog', 'frog', 'cat', 'hat', 'god' ]) .takeWhile(x => x.match(/o/)) // List [ "dog", "frog" ]run it

takeUntil()

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: number, iter: this) => boolean,
context?: unknown
): this

Inherited from

Collection#takeUntil()

Discussion

const { List } = require('immutable') List([ 'dog', 'frog', 'cat', 'hat', 'god' ]) .takeUntil(x => x.match(/at/)) // List [ "dog", "frog" ]run it

Reducing a value

reduce()

reduce<R>(reducer: (reduction: R, value: T, key: number, iter: this) => R,
initialReduction: R,
context?: unknown
): R
reduce<R>(reducer: (reduction: T | R, value: T, key: number, iter: this) => R
): R

Inherited from

Collection#reduce()

reduceRight()

reduceRight<R>(reducer: (reduction: R, value: T, key: number, iter: this) => R,
initialReduction: R,
context?: unknown
): R
reduceRight<R>(reducer: (reduction: T | R, value: T, key: number, iter: this) => R
): R

Inherited from

Collection#reduceRight()

every()

True if predicate returns true for all entries in the Collection.

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

Inherited from

Collection#every()

some()

True if predicate returns true for any entry in the Collection.

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

Inherited from

Collection#some()

join()

Joins values together as a string, inserting a separator between each. The default separator is ",".

join(separator?: string): string

Inherited from

Collection#join()

isEmpty()

Returns true if this Collection includes no values.

isEmpty(): boolean

Inherited from

Collection#isEmpty()

Discussion

For some lazy Seq, isEmpty might need to iterate to determine emptiness. At most one iteration will occur.

count()

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

Inherited from

Collection#count()

countBy()

Returns a Seq.Keyed of counts, grouped by the return value of the grouper function.

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

Inherited from

Collection#countBy()

Discussion

Note: This is not a lazy operation.

Comparison

isSubset()

True if iter includes every value in this Collection.

isSubset(iter: Iterable<T>): boolean

Inherited from

Collection#isSubset()

isSuperset()

True if this Collection includes every value in iter.

isSuperset(iter: Iterable<T>): boolean

Inherited from

Collection#isSuperset()

This documentation is generated from immutable.d.ts. Pull requests and Issues welcome.

Immutable.js

Construction

Static Methods

Members

Persistent changes

Deep persistent changes

Transient changes

Sequence algorithms

Conversion to JavaScript types

Reading values

Conversion to Seq

Combination

Search for value

Value equality

Reading deep values

Conversion to Collections

Iterators

Collections (Seq)

Side effects

Creating subsets

Reducing a value

Comparison

List

Discussion

Construction

Discussion

Static methods

Members

Persistent changes

Discussion

alias

Discussion

Discussion

Discussion

Discussion

Discussion

Discussion

Discussion

Overrides

Discussion

Deep persistent changes

Discussion

alias

Discussion

see

see

Transient changes

see

see

Discussion

see

see

Sequence algorithms

Overrides

alias

Discussion

Overrides

Discussion

Overrides

Discussion

Overrides

Overrides

Overrides

Overrides

Overrides

Inherited from

Inherited from

Discussion

Inherited from

Inherited from

Discussion

Inherited from

Discussion

Inherited from

Discussion

Conversion to JavaScript types

Inherited from

Inherited from

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