The yin to asMutable's yang. Because it applies to mutable collections,
this operation is mutable and may return itself (though may not
return itself, i.e. if the result is an empty collection). Once
performed, the original mutable copy must no longer be mutated since it
may be the immutable result.
If possible, use withMutations to work with temporary mutable copies as
it provides an easier to use API and considers many common optimizations.
Another way to avoid creation of intermediate Immutable maps is to create
a mutable copy of this collection. Mutable copies always return this,
and thus shouldn't be used for equality. Your function should never return
a mutable copy of a collection, only use it internally to create a new
collection.
If possible, use withMutations to work with temporary mutable copies as
it provides an easier to use API and considers many common optimizations.
Note: if the collection is already mutable, asMutable returns itself.
Note: Not all methods can be used on a mutable collection or within
withMutations! Read the documentation for each method to see if it
is safe to use in withMutations.
Returns a new Collection of the same type containing all entries except the last.
Returns a new Map containing no keys or values.
const { Map } = require('immutable')
Map({ key: 'value' }).clear()
// Map {}
Note: clear can be used in withMutations.
Returns the size of this Collection.
Regardless of if this Collection can describe its size lazily (some Seqs
cannot), this method will always return the correct size. E.g. it
evaluates a lazy Seq if necessary.
If predicate is provided, then this returns the count of entries in the
Collection for which the predicate returns true.
Returns a new Map which excludes this key.
Note: delete cannot be safely used in IE8, but is provided to mirror
the ES6 collection API.
const { Map } = require('immutable')
const originalMap = Map({
key: 'value',
otherKey: 'other value'
})
// Map { "key": "value", "otherKey": "other value" }
originalMap.delete('otherKey')
// Map { "key": "value" }
Note: delete can be used in withMutations.
Returns a new Map having removed the value at this keyPath. If any keys
in keyPath do not exist, no change will occur.
Note: deleteIn can be used in withMutations.
True if this and the other Collection have value equality, as defined
by Immutable.is().
Note: This is equivalent to Immutable.is(this, other), but provided to
allow for chained expressions.
Returns a new Map with only the entries for which the predicate
function returns true.
Note: filter() always returns a new instance, even if it results in
not filtering out any values.
Returns a new Collection of the same type with only the entries for which
the predicate function returns false.
const { Map } = require('immutable')
Map({ a: 1, b: 2, c: 3, d: 4}).filterNot(x => x % 2 === 0)
// Map { "a": 1, "c": 3 }
Note: filterNot() always returns a new instance, even if it results in
not filtering out any values.
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.
Note: flatten(true) operates on Collection<any, Collection<K, V>> and
returns Collection<K, V>
Optionaldepth: numberOptionalshallow: booleanThe sideEffect is executed for every entry in the Collection.
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 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.
Returns the value found by following a path of keys or indices through nested Collections.
const { Map, List } = require('immutable')
const deepData = Map({ x: List([ Map({ y: 123 }) ]) });
deepData.getIn(['x', 0, 'y']) // 123
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']) // 123
OptionalnotSetValue: anyReturns a Collection.Keyed of Collection.Keyeds, grouped by the return
value of the grouper function.
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 } ],
// }
True if a key exists within this Collection, using Immutable.is
to determine equality
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.
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);
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.
True if the result of following a path of keys or indices through nested Collections results in a set value.
True if a value exists within this Collection, using Immutable.is
to determine equality
Returns true if this Collection includes no values.
For some lazy Seq, isEmpty might need to iterate to determine
emptiness. At most one iteration will occur.
Joins values together as a string, inserting a separator between each.
The default separator is ",".
Optionalseparator: stringAn iterator of this Collection's 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.
Returns a new Seq.Indexed of the keys of this Collection, discarding values.
Returns the maximum value in this collection. If any values are comparatively equivalent, the first one found will be returned.
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:
hitters.maxBy(hitter => hitter.avgHits);
Returns a new Map resulting from merging the provided Collections (or JS objects) into this Map. In other words, this takes each entry of each collection and sets it on this Map.
Note: Values provided to merge are shallowly converted before being
merged. No nested values are altered.
const { Map } = require('immutable')
const one = Map({ a: 10, b: 20, c: 30 })
const two = Map({ b: 40, a: 50, d: 60 })
one.merge(two) // Map { "a": 50, "b": 40, "c": 30, "d": 60 }
two.merge(one) // Map { "b": 20, "a": 10, "d": 60, "c": 30 }
Note: merge can be used in withMutations.
Like merge(), but when two Collections conflict, it merges them as well,
recursing deeply through the nested data.
Note: Values provided to merge are shallowly converted before being
merged. No nested values are altered unless they will also be merged at
a deeper level.
const { Map } = require('immutable')
const one = Map({ a: Map({ x: 10, y: 10 }), b: Map({ x: 20, y: 50 }) })
const two = Map({ a: Map({ x: 2 }), b: Map({ y: 5 }), c: Map({ z: 3 }) })
one.mergeDeep(two)
// Map {
// "a": Map { "x": 2, "y": 10 },
// "b": Map { "x": 20, "y": 5 },
// "c": Map { "z": 3 }
// }
Note: mergeDeep can be used in withMutations.
A combination of updateIn and mergeDeep, returning a new Map, but
performing the deep merge at a point arrived at by following the keyPath.
In other words, these two lines are equivalent:
map.updateIn(['a', 'b', 'c'], abc => abc.mergeDeep(y))
map.mergeDeepIn(['a', 'b', 'c'], y)
Note: mergeDeepIn can be used in withMutations.
Like mergeDeep(), but when two non-Collections conflict, it uses the
merger function to determine the resulting value.
const { Map } = require('immutable')
const one = Map({ a: Map({ x: 10, y: 10 }), b: Map({ x: 20, y: 50 }) })
const two = Map({ a: Map({ x: 2 }), b: Map({ y: 5 }), c: Map({ z: 3 }) })
one.mergeDeepWith((oldVal, newVal) => oldVal / newVal, two)
// Map {
// "a": Map { "x": 5, "y": 10 },
// "b": Map { "x": 20, "y": 10 },
// "c": Map { "z": 3 }
// }
Note: mergeDeepWith can be used in withMutations.
A combination of updateIn and merge, returning a new Map, but
performing the merge at a point arrived at by following the keyPath.
In other words, these two lines are equivalent:
map.updateIn(['a', 'b', 'c'], abc => abc.merge(y))
map.mergeIn(['a', 'b', 'c'], y)
Note: mergeIn can be used in withMutations.
Like merge(), mergeWith() returns a new Map resulting from merging
the provided Collections (or JS objects) into this Map, but uses the
merger function for dealing with conflicts.
const { Map } = require('immutable')
const one = Map({ a: 10, b: 20, c: 30 })
const two = Map({ b: 40, a: 50, d: 60 })
one.mergeWith((oldVal, newVal) => oldVal / newVal, two)
// { "a": 0.2, "b": 0.5, "c": 30, "d": 60 }
two.mergeWith((oldVal, newVal) => oldVal / newVal, one)
// { "b": 2, "a": 5, "d": 60, "c": 30 }
Note: mergeWith can be used in withMutations.
Returns the minimum value in this collection. If any values are comparatively equivalent, the first one found will be returned.
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:
hitters.minBy(hitter => hitter.avgHits);
Reduces the Collection to a value by calling the reducer for every entry
in the Collection and passing along the reduced value.
If initialReduction is not provided, the first item in the
Collection will be used.
Returns a new Collection of the same type containing all entries except the first.
Returns a new Collection of the same type in reverse order.
Returns a new Map also containing the new key, value pair. If an equivalent key already exists in this Map, it will be replaced.
const { Map } = require('immutable')
const originalMap = Map()
const newerMap = originalMap.set('key', 'value')
const newestMap = newerMap.set('key', 'newer value')
originalMap
// Map {}
newerMap
// Map { "key": "value" }
newestMap
// Map { "key": "newer value" }
Note: set can be used in withMutations.
Returns a new Map having set value at this keyPath. If any keys in
keyPath do not exist, a new immutable Map will be created at that key.
const { Map } = require('immutable')
const originalMap = Map({
subObject: Map({
subKey: 'subvalue',
subSubObject: Map({
subSubKey: 'subSubValue'
})
})
})
const newMap = originalMap.setIn(['subObject', 'subKey'], 'ha ha!')
// Map {
// "subObject": Map {
// "subKey": "ha ha!",
// "subSubObject": Map { "subSubKey": "subSubValue" }
// }
// }
const newerMap = originalMap.setIn(
['subObject', 'subSubObject', 'subSubKey'],
'ha ha ha!'
)
// Map {
// "subObject": Map {
// "subKey": "subvalue",
// "subSubObject": Map { "subSubKey": "ha ha ha!" }
// }
// }
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 { Map } = require('immutable')
const originalMap = Map({
subObject: {
subKey: 'subvalue',
subSubObject: {
subSubKey: 'subSubValue'
}
}
})
originalMap.setIn(['subObject', 'subKey'], 'ha ha!')
// Map {
// "subObject": {
// subKey: "ha ha!",
// subSubObject: { subSubKey: "subSubValue" }
// }
// }
If any key in the path exists but cannot be updated (such as a primitive like number or a custom Object like Date), an error will be thrown.
Note: setIn can be used in withMutations.
Returns a new Collection of the same type which excludes the first amount
entries from this Collection.
Returns a new Collection of the same type which excludes the last amount
entries from this Collection.
Returns a new Collection of the same type which includes entries starting
from when predicate first returns true.
const { List } = require('immutable')
List([ 'dog', 'frog', 'cat', 'hat', 'god' ])
.skipUntil(x => x.match(/hat/))
// List [ "hat", "god"" ]
Returns a new Collection of the same type which includes entries starting
from when predicate first returns false.
const { List } = require('immutable')
List([ 'dog', 'frog', 'cat', 'hat', 'god' ])
.skipWhile(x => x.match(/g/))
// List [ "cat", "hat", "god"" ]
Returns a new Collection of the same type representing a portion of this Collection from start up to but not including end.
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.
Optionalbegin: numberOptionalend: numberReturns a new Collection of the same type which includes the same entries,
stably sorted by using a comparator.
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 valueB1 (or any positive number) if valueA comes after valueBWhen 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 }
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:
hitters.sortBy(hitter => hitter.avgHits)
Note: sortBy() Always returns a new instance, even if the original was
already sorted.
Note: This is always an eager operation.
Returns a new Collection of the same type which includes the first amount
entries from this Collection.
Returns a new Collection of the same type which includes the last amount
entries from this Collection.
Returns a new Collection of the same type which includes entries from this
Collection as long as the predicate returns false.
const { List } = require('immutable')
List([ 'dog', 'frog', 'cat', 'hat', 'god' ])
.takeUntil(x => x.match(/at/))
// List [ "dog", "frog" ]
Returns a new Collection of the same type which includes entries from this
Collection as long as the predicate returns true.
const { List } = require('immutable')
List([ 'dog', 'frog', 'cat', 'hat', 'god' ])
.takeWhile(x => x.match(/o/))
// List [ "dog", "frog" ]
Returns an Seq.Indexed of the values of this Collection, discarding keys.
Deeply converts this Keyed collection to equivalent native JavaScript Object.
Converts keys to Strings.
Shallowly converts this Keyed collection to equivalent native JavaScript Object.
Converts keys to Strings.
Returns a Seq.Keyed from this Collection where indices are treated as keys.
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" }
Converts this Collection to a List, discarding keys.
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" ]
Converts this Collection to a Map, Throws if keys are not hashable.
Note: This is equivalent to Map(this.toKeyedSeq()), but provided
for convenience and to allow for chained expressions.
Shallowly converts this Collection to an Object.
Converts keys to Strings.
Converts this Collection to a Map, maintaining the order of iteration.
Note: This is equivalent to OrderedMap(this.toKeyedSeq()), but
provided for convenience and to allow for chained expressions.
Converts this Collection to a Set, maintaining the order of iteration and discarding keys.
Note: This is equivalent to OrderedSet(this.valueSeq()), but provided
for convenience and to allow for chained expressions.
Converts this Collection to a Set, discarding keys. Throws if values are not hashable.
Note: This is equivalent to Set(this), but provided to allow for
chained expressions.
Returns a new Map having updated the value at this key with the return
value of calling updater with the existing value.
Similar to: map.set(key, updater(map.get(key))).
const { Map } = require('immutable')
const aMap = Map({ key: 'value' })
const newMap = aMap.update('key', value => value + value)
// Map { "key": "valuevalue" }
This is most commonly used to call methods on collections within a
structure of data. For example, in order to .push() onto a nested List,
update and push can be used together:
const aMap = Map({ nestedList: List([ 1, 2, 3 ]) })
const newMap = aMap.update('nestedList', list => list.push(4))
// Map { "nestedList": List [ 1, 2, 3, 4 ] }
When a notSetValue is provided, it is provided to the updater
function when the value at the key does not exist in the Map.
const aMap = Map({ key: 'value' })
const newMap = aMap.update('noKey', 'no value', value => value + value)
// Map { "key": "value", "noKey": "no valueno value" }
However, if the updater function returns the same value it was called
with, then no change will occur. This is still true if notSetValue
is provided.
const aMap = Map({ apples: 10 })
const newMap = aMap.update('oranges', 0, val => val)
// Map { "apples": 10 }
assert.strictEqual(newMap, map);
For code using ES2015 or later, using notSetValue is discourged in
favor of function parameter default values. This helps to avoid any
potential confusion with identify functions as described above.
The previous example behaves differently when written with default values:
const aMap = Map({ apples: 10 })
const newMap = aMap.update('oranges', (val = 0) => val)
// Map { "apples": 10, "oranges": 0 }
If no key is provided, then the updater function return value is
returned as well.
const aMap = Map({ key: 'value' })
const result = aMap.update(aMap => aMap.get('key'))
// "value"
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".
For example, to sum the values in a Map
function sum(collection) {
return collection.reduce((sum, x) => sum + x, 0)
}
Map({ x: 1, y: 2, z: 3 })
.map(x => x + 1)
.filter(x => x % 2 === 0)
.update(sum)
// 6
Note: update(key) can be used in withMutations.
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".
For example, to sum a Seq after mapping and filtering:
const { Seq } = require('immutable')
function sum(collection) {
return collection.reduce((sum, x) => sum + x, 0)
}
Seq([ 1, 2, 3 ])
.map(x => x + 1)
.filter(x => x % 2 === 0)
.update(sum)
// 6
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".
For example, to sum a Seq after mapping and filtering:
const { Seq } = require('immutable')
function sum(collection) {
return collection.reduce((sum, x) => sum + x, 0)
}
Seq([ 1, 2, 3 ])
.map(x => x + 1)
.filter(x => x % 2 === 0)
.update(sum)
// 6
Returns a new Map having applied the updater to the entry found at the
keyPath.
This is most commonly used to call methods on collections nested within a
structure of data. For example, in order to .push() onto a nested List,
updateIn and push can be used together:
const { Map, List } = require('immutable')
const map = Map({ inMap: Map({ inList: List([ 1, 2, 3 ]) }) })
const newMap = map.updateIn(['inMap', 'inList'], list => list.push(4))
// Map { "inMap": Map { "inList": List [ 1, 2, 3, 4 ] } }
If any keys in keyPath do not exist, new Immutable Maps will
be created at those keys. If the keyPath does not already contain a
value, the updater function will be called with notSetValue, if
provided, otherwise undefined.
const map = Map({ a: Map({ b: Map({ c: 10 }) }) })
const newMap = map.updateIn(['a', 'b', 'c'], val => val * 2)
// Map { "a": Map { "b": Map { "c": 20 } } }
If the updater function returns the same value it was called with, then
no change will occur. This is still true if notSetValue is provided.
const map = Map({ a: Map({ b: Map({ c: 10 }) }) })
const newMap = map.updateIn(['a', 'b', 'x'], 100, val => val)
// Map { "a": Map { "b": Map { "c": 10 } } }
assert.strictEqual(newMap, aMap)
For code using ES2015 or later, using notSetValue is discourged in
favor of function parameter default values. This helps to avoid any
potential confusion with identify functions as described above.
The previous example behaves differently when written with default values:
const map = Map({ a: Map({ b: Map({ c: 10 }) }) })
const newMap = map.updateIn(['a', 'b', 'x'], (val = 100) => val)
// Map { "a": Map { "b": Map { "c": 10, "x": 100 } } }
Plain JavaScript Object or Arrays may be nested within an Immutable.js Collection, and updateIn() can update those values as well, treating them immutably by creating new copies of those values with the changes applied.
const map = Map({ a: { b: { c: 10 } } })
const newMap = map.updateIn(['a', 'b', 'c'], val => val * 2)
// Map { "a": { b: { c: 20 } } }
If any key in the path exists but cannot be updated (such as a primitive like number or a custom Object like Date), an error will be thrown.
Note: updateIn can be used in withMutations.
An iterator of this Collection's 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.
Returns an Seq.Indexed of the values of this Collection, discarding keys.
Every time you call one of the above functions, a new immutable Map is created. If a pure function calls a number of these to produce a final return value, then a penalty on performance and memory has been paid by creating all of the intermediate immutable Maps.
If you need to apply a series of mutations to produce a new immutable
Map, withMutations() creates a temporary mutable copy of the Map which
can apply mutations in a highly performant manner. In fact, this is
exactly how complex mutations like merge are done.
As an example, this results in the creation of 2, not 4, new Maps:
const { Map } = require('immutable')
const map1 = Map()
const map2 = map1.withMutations(map => {
map.set('a', 1).set('b', 2).set('c', 3)
})
assert.equal(map1.size, 0)
assert.equal(map2.size, 3)
Note: Not all methods can be used on a mutable collection or within
withMutations! Read the documentation for each method to see if it
is safe to use in withMutations.
The number of entries in this Map.