Readonly sizeThe 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.
Map#asMutable
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.
Map#asImmutable
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.
Optional context: unknownReturns a Seq.Keyed of counts, grouped by the return value of
the grouper function.
Note: This is not a lazy operation.
Optional context: unknownReturns 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.
remove
Returns a new Map which excludes the provided keys.
const { Map } = require('immutable')
const names = Map({ a: "Aaron", b: "Barry", c: "Connor" })
names.deleteAll([ 'a', 'c' ])
// Map { "b": "Barry" }
Note: deleteAll can be used in withMutations.
removeAll
True if predicate returns true for all entries in the Collection.
Optional context: unknownReturns 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.
Optional context: unknownOptional context: unknownReturns 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.
Optional context: unknownReturns the first value for which the predicate returns true.
Optional context: unknownOptional notSetValue: VReturns the first [key, value] entry for which the predicate returns true.
Optional context: unknownOptional notSetValue: VReturns the key for which the predicate returns true.
Optional context: unknownReturns the last value for which the predicate returns true.
Note: predicate will be called for each entry in reverse.
Optional context: unknownOptional notSetValue: VReturns the last [key, value] entry for which the predicate
returns true.
Note: predicate will be called for each entry in reverse.
Optional context: unknownOptional notSetValue: VReturns the last key for which the predicate returns true.
Note: predicate will be called for each entry in reverse.
Optional context: unknownIn 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.
Optional notSetValue: NSVFlat-maps the Map, returning a new Map.
Similar to data.map(...).flatten(true).
Optional context: unknownFlattens 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<unknown, Collection<K, V>> and
returns Collection<K, V>
Optional depth: numberOptional shallow: 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).
Optional context: unknownReturns a sequence representing a portion of this sorted map starting with a specific key up to the last entry in the sorted map. If the optional parameter backwards is set to true, the returned sequence will list the entries backwards, starting with key down to the first entry in the sorted map,
Example:
> const abc = SortedMap([["A", "a"], ["B", "b"], ["C", "c"], ["D", "d"], ["E", "e"], ["F", "f"], ["G", "g"], ["H", "h"], ["I", "i"], ["J", "j"], ["K", "k"], ["L", "l"], ["M", "m"], ["N", "n"], ["O", "o"], ["P", "p"], ["Q", "q"], ["R", "r"], ["S", "s"], ["T", "t"], ["U", "u"], ["V", "v"], ["W", "w"], ["X", "x"], ["Y", "y"], ["Z", "z"]]);
> abc.from("R");
Seq { "R": "r", "S": "s", "T": "t", "U": "u", "V": "v", "W": "w", "X": "x", "Y": "y", "Z": "z" }
> abc.from("R", true);
Seq { "R": "r", "Q": "q", "P": "p", "O": "o", "N": "n", "M": "m", "L": "l", "K": "k", "J": "j", "I": "i", "H": "h", "G": "g", "F": "f", "E": "e", "D": "d", "C": "c", "B": "b", "A": "a" }
The method from() can be efficiently combined with take() to retrieve the desired number of values or with takeWhile() to retrieve a specific range:
> abc.from("R").take(5);
Seq { "R": "r", "S": "s", "T": "t", "U": "u", "V": "v" }
> abc.from("R").takeWhile((v, k) => k < "W");
Seq { "R": "r", "S": "s", "T": "t", "U": "u", "V": "v" }
> abc.from("R", true).take(5);
Seq { "R": "r", "Q": "q", "P": "p", "O": "o", "N": "n" }
> abc.from("R", true).takeWhile((v, k) => k > "K");
Seq { "R": "r", "Q": "q", "P": "p", "O": "o", "N": "n", "M": "m", "L": "l" }
Optional backwards: booleanReturns a sequence representing a portion of this sorted map starting from numeric index position, as if the collection was an array. If the optional parameter backwards is set to true, the returned sequence will list the entries backwards.
The method is optimized to quickly find the n-th entry inside the b-tree structure by checking the computed sizes of underlying nodes. Even though the algorithm is not as fast as working with a native array, it is faster by orders of magnitude than walking through the first n elements of unindexed collection to just skip them. The access time is O(log N).
Example:
> const abc = SortedMap([["A", "a"], ["B", "b"], ["C", "c"], ["D", "d"], ["E", "e"], ["F", "f"], ["G", "g"], ["H", "h"], ["I", "i"], ["J", "j"], ["K", "k"], ["L", "l"], ["M", "m"], ["N", "n"], ["O", "o"], ["P", "p"], ["Q", "q"], ["R", "r"], ["S", "s"], ["T", "t"], ["U", "u"], ["V", "v"], ["W", "w"], ["X", "x"], ["Y", "y"], ["Z", "z"]]);
> abc.fromIndex(4).take(5);
Seq { "E": "e", "F": "f", "G": "g", "H": "h", "I": "i" }
> abc.fromIndex(4, true).take(5);
Seq { "E": "e", "D": "d", "C": "c", "B": "b", "A": "a" }
Optional backwards: booleanReturns 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
Optional notSetValue: unknownReturns a Map of Collection, 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 } ],
// }
Optional context: unknownComputes 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.
The incremental sort optimized to provide first entries of the result set faster than regular sort(). Similarly to partialSort() it is using the Floyd-Rivest select algorithm. The incremental sort doesn't cache its results as it is supposed to be used with iterators retrieving limited number of result entries.
Optional comparator: ((valueA, valueB) => number)Like incSort, but also accepts a comparatorValueMapper which allows for
sorting by more sophisticated means:
hitters.incSortBy(hitter => hitter.avgHits)
Optional comparator: ((valueA, valueB) => number)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.
Optional notSetValue: NSVReturns a new Map with values passed through a
mapper function.
Map({ a: 1, b: 2 }).map(x => 10 * x)
// Map { a: 10, b: 20 }
Optional context: unknownOptional context: unknownCollection.Keyed.mapEntries
Optional context: unknownCollection.Keyed.mapKeys
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.
Optional comparator: Comparator<V>Like max, but also accepts a comparatorValueMapper which allows for
comparing by more sophisticated means:
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 }
Optional comparator: Comparator<C>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.
Rest ...collections: Iterable<[KC, VC]>[]concat
Rest ...collections: { Like merge(), but when two compatible collections are encountered with
the same key, it merges them as well, recursing deeply through the nested
data. Two collections are considered to be compatible (and thus will be
merged together) if they both fall into one of three categories: keyed
(e.g., Maps, Records, and objects), indexed (e.g., Lists and
arrays), or set-like (e.g., Sets). If they fall into separate
categories, mergeDeep will replace the existing collection with the
collection being merged in. This behavior can be customized by using
mergeDeepWith().
Note: Indexed and set-like collections are merged using
concat()/union() and therefore do not recurse.
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.
Rest ...collections: (Iterable<[K, V]> | { 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.
Rest ...collections: unknown[]Like mergeDeep(), but when two non-collections or incompatible
collections are encountered at the same key, it uses the merger
function to determine the resulting value. Collections are considered
incompatible if they fall into separate categories between keyed,
indexed, and set-like.
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.
Rest ...collections: (Iterable<[K, V]> | { 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.
Rest ...collections: unknown[]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.
Rest ...collections: (Iterable<[K, V]> | { 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.
Optional comparator: Comparator<V>Like min, but also accepts a comparatorValueMapper which allows for
comparing by more sophisticated means:
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 }
Optional comparator: Comparator<C>Returns a new SortedMap containing the entries of the provided
collection-like. The entries will be organized in an optimized tree structure
with internal nodes and leaves defragmented as much as possible
while keeping all the consistency rules enforced.
If the collection argument is undefined then the current content
of this SortedMap will be reorganized into an optimized tree structure.
The pack procedure is actually called from the SortedMap constructor
as it is usually faster than a series of set operations. It is recommended
to explicitly call this method after a large batch of update or delete operations
to release a portion of the allocated memory and to speed up the consequent get
operations.
Optional collection: Iterable<[K, V]>Like partialSort, but also accepts a comparatorValueMapper which allows for
sorting by more sophisticated means:
hitters.partialSortBy(10, hitter => hitter.avgHits)
Optional comparator: ((valueA, valueB) => number)Returns a new Map with the values for which the predicate
function returns false and another for which is returns true.
Optional context: COptional context: CPrints out the internal Btree structure of the SortedMap.
Keeps printing the nodes recursively until maxDepth level is reached.
const { SortedMap } = require('@oraichain/immutable')
const aSortedMap = Range(0, 8).toSortedMap(undefined, {btreeOrder: 4});
sortedMap.print();
+ LEAF[0] (L0)
- ENTRY[0]: 0
- ENTRY[1]: 1
- ENTRY[0]: 2
+ LEAF[1] (L0)
- ENTRY[0]: 3
- ENTRY[1]: 4
- ENTRY[1]: 5
+ LEAF[2] (L0)
- ENTRY[0]: 6
- ENTRY[1]: 7
Optional maxDepth: numberReduces 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.
Optional context: unknownArray#reduce.
Reduces the Collection in reverse (from the right side).
Note: Similar to this.reverse().reduce(), and provided for parity
with Array#reduceRight.
Optional context: unknownReturns 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 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" ]
Optional context: unknownReturns 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" ]
Optional context: unknownReturns 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.
Optional begin: numberOptional end: numberTrue if predicate returns true for any entry in the Collection.
Optional context: unknownReturns 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 valueBPairSorting 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 }
Note: sort() Always returns a new instance, even if the original was
already sorted.
Note: This is always an eager operation.
Optional comparator: Comparator<V>Like sort, but also accepts a comparatorValueMapper which allows for
sorting by more sophisticated means:
const { Map } = require('immutable')
const beattles = Map({
John: { name: "Lennon" },
Paul: { name: "McCartney" },
George: { name: "Harrison" },
Ringo: { name: "Starr" },
});
beattles.sortBy(member => member.name);
Note: sortBy() Always returns a new instance, even if the original was
already sorted.
Note: This is always an eager operation.
Optional comparator: Comparator<C>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" ]
Optional context: unknownReturns 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" ]
Optional context: unknownReturns 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 SortedMap, with entries sorted according to comparator
If comparator is undefined then defaultComparator will be applied.
Note: This is equivalent to SortedMap(this.toKeyedSeq()), but
provided for convenience and to allow for chained expressions.
Optional comparator: ((a, b) => number)Optional options: { Converts this Collection to a SortedSet, maintaining the order of iteration and discarding keys.
Note: This is equivalent to SortedSet(this.valueSeq()), but provided
for convenience and to allow for chained expressions.
Optional comparator: ((a, b) => number)Optional options: { 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.
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.
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.
Generated using TypeDoc
The number of entries (key/value pairs) in this SortedMap.