Collection.Indexed

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

Converts keys to Strings.

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.

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

The shortest Collection stops interleave.

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

Note: interleave cannot be used in withMutations.

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.

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

Note: splice cannot be used in withMutations.

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

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

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

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.

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

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.

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

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

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

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.

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

comparator(valueA, valueB):

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

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

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

Note: This is always an eager operation.

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.

Note: This is always an eager operation.

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

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.

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.

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

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

Seq([ 1, 2, 3 ]) .map(x => x + 1) .filter(x => x % 2 === 0) .update(sum) // 6run it

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

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

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

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

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.

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

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

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

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

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).

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.

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

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

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

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

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

Note: This is not a lazy operation.