Lists are ordered indexed dense collections, much like a JavaScript Array.
type List<T> extends Collection.Indexed<T>
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.
Create a new immutable List containing the values of the provided collection-like.
List<T>(collection?: Iterable<T> | ArrayLike<T>): List<T>
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
List.isList(maybeList: unknown): boolean
The number of items in this List.
size: number
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>
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
.
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>
remove()
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
.
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>
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
.
Returns a new List with 0 size and no values in constant time.
clear(): List<T>
List([ 1, 2, 3, 4 ]).clear()
// List []run it
Note: clear
can be used in withMutations
.
Returns a new List with the provided values
appended, starting at this
List's size
.
push(...values: Array<T>): List<T>
List([ 1, 2, 3, 4 ]).push(5)
// List [ 1, 2, 3, 4, 5 ]run it
Note: push
can be used in withMutations
.
Returns a new List with a size ones less than this List, excluding the last index in this List.
pop(): List<T>
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
.
Returns a new List with the provided values
prepended, shifting other
values ahead to higher indices.
unshift(...values: Array<T>): List<T>
List([ 2, 3, 4]).unshift(1);
// List [ 1, 2, 3, 4 ]run it
Note: unshift
can be used in withMutations
.
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>
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(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
Collection#update()
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>
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.
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
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
.
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
removeIn()
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(keyPath: Iterable<unknown>,
notSetValue: unknown,
updater: (value: unknown) => unknown): this
updateIn(keyPath: Iterable<unknown>, updater: (value: unknown) => unknown): this
Note: mergeIn
can be used in withMutations
.
mergeIn(keyPath: Iterable<unknown>, ...collections: Array<unknown>): this
Note: mergeDeepIn
can be used in withMutations
.
mergeDeepIn(keyPath: Iterable<unknown>, ...collections: Array<unknown>): this
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
An alternative API for withMutations()
asMutable(): this
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(): boolean
asImmutable(): this
Returns a new List with other values or collections concatenated to this one.
concat<C>(...valuesOrCollections: Array<Iterable<C> | C>): List<T | C>
Collection.Indexed#concat()
merge()
Note: concat
can be used in withMutations
.
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>
Collection.Indexed#map()
List([ 1, 2 ]).map(x => 10 * x)
// List [ 10, 20 ]run it
Flat-maps the List, returning a new List.
flatMap<M>(mapper: (value: T, key: number, iter: this) => Iterable<M>,
context?: unknown): List<M>
Collection.Indexed#flatMap()
Similar to list.map(...).flatten(true)
.
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
Collection.Indexed#filter()
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]
Collection.Indexed#partition()
zip<U>(other: Collection<unknown, U>): List<[T, U]>
zip<U, V>(): List<[T, U, V]>
zip(...collections: Array<Collection<unknown, unknown>>): List<unknown>
Collection.Indexed#zip()
zipAll<U>(other: Collection<unknown, U>): List<[T, U]>
zipAll<U, V>(): List<[T, U, V]>
zipAll(...collections: Array<Collection<unknown, unknown>>): List<unknown>
Collection.Indexed#zipAll()
zipWith<U, Z>(): 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>
Collection.Indexed#zipWith()
[Symbol.iterator](): IterableIterator<T>
Collection.Indexed#[Symbol.iterator]()
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
Collection#filterNot()
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.
Returns a new Collection of the same type in reverse order.
reverse(): this
Collection#reverse()
Returns a new Collection of the same type which includes the same entries,
stably sorted by using a comparator
.
sort(comparator?: Comparator<T>): this
Collection#sort()
If a comparator
is not provided, a default comparator uses <
and >
.
comparator(valueA, valueB)
:
0
if the elements should not be swapped.-1
(or any negative number) if valueA
comes before valueB
1
(or any positive number) if valueA
comes after valueB
PairSorting
enum typeWhen 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.
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
Collection#sortBy()
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.
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>
Collection#groupBy()
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
Deeply converts this Indexed collection to equivalent native JavaScript Array.
toJS(): Array<DeepCopy<T>>
Collection.Indexed#toJS()
Shallowly converts this Indexed collection to equivalent native JavaScript Array.
toJSON(): Array<T>
Collection.Indexed#toJSON()
Shallowly converts this collection to an Array.
toArray(): Array<T>
Collection.Indexed#toArray()
Shallowly converts this Collection to an Object.
toObject(): {[key: string]: T}
Collection#toObject()
Converts keys to Strings.
get<NSV>(index: number, notSetValue: NSV): T | NSV
get(index: number): T | undefined
Collection.Indexed#get()
True if a key exists within this Collection
, using Immutable.is
to determine equality
has(key: number): boolean
Collection#has()
True if a value exists within this Collection
, using Immutable.is
to determine equality
includes(value: T): boolean
Collection#includes()
contains()
In case the Collection
is not empty returns the first element of the
Collection
.
In case the Collection
is empty returns the optional default
value if provided, if no default value is provided returns undefined.
first<NSV>(notSetValue?: NSV): T | NSV
Collection#first()
In case the Collection
is not empty returns the last element of the
Collection
.
In case the Collection
is empty returns the optional default
value if provided, if no default value is provided returns undefined.
last<NSV>(notSetValue?: NSV): T | NSV
Collection#last()
If this is a collection of [key, value] entry tuples, it will return a Seq.Keyed of those entries.
fromEntrySeq(): Seq.Keyed<unknown, unknown>
Collection.Indexed#fromEntrySeq()
Returns a Seq.Keyed from this Collection where indices are treated as keys.
toKeyedSeq(): Seq.Keyed<number, T>
Collection#toKeyedSeq()
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
Returns an Seq.Indexed of the values of this Collection, discarding keys.
toIndexedSeq(): Seq.Indexed<T>
Collection#toIndexedSeq()
Returns a Seq.Set of the values of this Collection, discarding keys.
toSetSeq(): Seq.Set<T>
Collection#toSetSeq()
Returns a Collection of the same type with separator
between each item
in this Collection.
interpose(separator: T): this
Collection.Indexed#interpose()
Returns a Collection of the same type with the provided collections
interleaved into this collection.
interleave(...collections: Array<Collection<unknown, T>>): this
Collection.Indexed#interleave()
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 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
Collection.Indexed#splice()
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
.
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
Collection.Indexed#indexOf()
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
Collection.Indexed#lastIndexOf()
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
Collection.Indexed#findIndex()
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
Collection.Indexed#findLastIndex()
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
Collection#find()
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
Collection#findLast()
Note: predicate
will be called for each entry in reverse.
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
Collection#findEntry()
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
Collection#findLastEntry()
Note: predicate
will be called for each entry in reverse.
Returns the key for which the predicate
returns true.
findKey(predicate: (value: T, key: number, iter: this) => boolean,
context?: unknown): number | undefined
Collection#findKey()
Returns the last key for which the predicate
returns true.
findLastKey(predicate: (value: T, key: number, iter: this) => boolean,
context?: unknown): number | undefined
Collection#findLastKey()
Note: predicate
will be called for each entry in reverse.
Returns the key associated with the search value, or undefined.
keyOf(searchValue: T): number | undefined
Collection#keyOf()
Returns the last key associated with the search value, or undefined.
lastKeyOf(searchValue: T): number | undefined
Collection#lastKeyOf()
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
Collection#max()
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: number, iter: this) => C,
comparator?: Comparator<C>): T | undefined
Collection#maxBy()
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
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
Collection#min()
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: number, iter: this) => C,
comparator?: Comparator<C>): T | undefined
Collection#minBy()
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
True if this and the other Collection have value equality, as defined
by Immutable.is()
.
equals(other: unknown): boolean
Collection#equals()
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.
hashCode(): number
Collection#hashCode()
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 hashCode
s,
they must not be equal.
Returns the value found by following a path of keys or indices through nested Collections.
getIn(searchKeyPath: Iterable<unknown>, notSetValue?: unknown): unknown
Collection#getIn()
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
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
Collection#hasIn()
Converts this Collection to a Map, Throws if keys are not hashable.
toMap(): Map<number, T>
Collection#toMap()
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<number, T>
Collection#toOrderedMap()
Note: This is equivalent to OrderedMap(this.toKeyedSeq())
, but
provided for convenience and to allow for chained expressions.
Converts this Collection to a Set, discarding keys. Throws if values are not hashable.
toSet(): Set<T>
Collection#toSet()
Note: This is equivalent to Set(this)
, but provided to allow for
chained expressions.
Converts this Collection to a Set, maintaining the order of iteration and discarding keys.
toOrderedSet(): OrderedSet<T>
Collection#toOrderedSet()
Note: This is equivalent to OrderedSet(this.valueSeq())
, but provided
for convenience and to allow for chained expressions.
Converts this Collection to a List, discarding keys.
toList(): List<T>
Collection#toList()
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
Converts this Collection to a Stack, discarding keys. Throws if values are not hashable.
toStack(): Stack<T>
Collection#toStack()
Note: This is equivalent to Stack(this)
, but provided to allow for
chained expressions.
An iterator of this Collection
's keys.
keys(): IterableIterator<number>
Collection#keys()
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 Collection
's values.
values(): IterableIterator<T>
Collection#values()
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 Collection
's entries as [ key, value ]
tuples.
entries(): IterableIterator<[number, T]>
Collection#entries()
Note: this will return an ES6 iterator which does not support
Immutable.js sequence algorithms. Use entrySeq
instead, if this is
what you want.
Returns a new Seq.Indexed of the keys of this Collection, discarding values.
keySeq(): Seq.Indexed<number>
Collection#keySeq()
Returns an Seq.Indexed of the values of this Collection, discarding keys.
valueSeq(): Seq.Indexed<T>
Collection#valueSeq()
Returns a new Seq.Indexed of [key, value] tuples.
entrySeq(): Seq.Indexed<[number, T]>
Collection#entrySeq()
The sideEffect
is executed for every entry in the Collection.
forEach(sideEffect: (value: T, key: number, iter: this) => unknown,
context?: unknown): number
Collection#forEach()
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).
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
Collection#slice()
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(): this
Collection#rest()
Returns a new Collection of the same type containing all entries except the last.
butLast(): this
Collection#butLast()
Returns a new Collection of the same type which excludes the first amount
entries from this Collection.
skip(amount: number): this
Collection#skip()
Returns a new Collection of the same type which excludes the last amount
entries from this Collection.
skipLast(amount: number): this
Collection#skipLast()
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
Collection#skipWhile()
const { List } = require('immutable')
List([ 'dog', 'frog', 'cat', 'hat', 'god' ])
.skipWhile(x => x.match(/g/))
// List [ "cat", "hat", "god" ]run it
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
Collection#skipUntil()
const { List } = require('immutable')
List([ 'dog', 'frog', 'cat', 'hat', 'god' ])
.skipUntil(x => x.match(/hat/))
// List [ "hat", "god" ]run it
Returns a new Collection of the same type which includes the first amount
entries from this Collection.
take(amount: number): this
Collection#take()
Returns a new Collection of the same type which includes the last amount
entries from this Collection.
takeLast(amount: number): this
Collection#takeLast()
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
Collection#takeWhile()
const { List } = require('immutable')
List([ 'dog', 'frog', 'cat', 'hat', 'god' ])
.takeWhile(x => x.match(/o/))
// List [ "dog", "frog" ]run it
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
Collection#takeUntil()
const { List } = require('immutable')
List([ 'dog', 'frog', 'cat', 'hat', 'god' ])
.takeUntil(x => x.match(/at/))
// List [ "dog", "frog" ]run it
flatten(depth?: number): Collection<unknown, unknown>
flatten(shallow?: boolean): Collection<unknown, unknown>
Collection#flatten()
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
Collection#reduce()
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
Collection#reduceRight()
True if predicate
returns true for all entries in the Collection.
every(predicate: (value: T, key: number, iter: this) => boolean,
context?: unknown): boolean
Collection#every()
True if predicate
returns true for any entry in the Collection.
some(predicate: (value: T, key: number, iter: this) => boolean,
context?: unknown): boolean
Collection#some()
Joins values together as a string, inserting a separator between each.
The default separator is ","
.
join(separator?: string): string
Collection#join()
Returns true if this Collection includes no values.
isEmpty(): boolean
Collection#isEmpty()
count(): number
count(predicate: (value: T, key: number, iter: this) => boolean,
context?: unknown): number
Collection#count()
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>
Collection#countBy()
Note: This is not a lazy operation.
True if iter
includes every value in this Collection.
isSubset(iter: Iterable<T>): boolean
Collection#isSubset()
True if this Collection includes every value in iter
.
isSuperset(iter: Iterable<T>): boolean
Collection#isSuperset()