kollectionjs - v2.0.0
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    kollectionjs - v2.0.0

    kollectionjs

    Lazy, chainable collection utilities for TypeScript, inspired by Kotlin's sequence API.

    Sequence<T> is a native subclass of Iterator<T>. Operations are lazy — nothing runs until a terminal call like toArray() or forEach().

    Github repo: https://github.com/geowarin/kollectionjs

    pnpm add kollectionjs

    const sequence = sequenceOf(1, 2, 3);
    let result = sequence
      .map(it => it * 2)
      .filter(it => it % 3 == 0)
      .toArray();

    expect(result).toEqual([6]);

    const result = entriesOf({ name: "yoda" })
      .mapKeys(k => k.toUpperCase())
      .mapValues(v => v.toUpperCase())
      .toObject();

    Full API documentation is available here.

    Description
    asSequence Wraps any Iterable in a Sequence
    concat Creates a Sequence that lazily concatenates all given iterables in order
    emptySequence Creates an empty Sequence
    entriesOf Creates a Sequence of [key, value] pairs from a plain object, equivalent to `asSequence(Object
    generate Creates an infinite (or finite) Sequence by repeatedly applying next to a seed value
    range Creates a Sequence of numbers from start (inclusive) to endExclusive (exclusive), advancing by step
    sequenceOf Creates a Sequence from the given arguments
    Description
    associate Returns a Map built by applying transform to each element and using the resulting [key, value] pair
    associateBy Returns a Map keyed by the result of keySelector (or a property name)
    associateWith Returns a Map where each element is the key and valueSelector provides the value
    average Returns the arithmetic mean of a numeric sequence
    chunk Splits the sequence into chunks of at most chunkSize elements
    contains Returns true if the sequence contains the given element (using ===)
    count Returns the number of elements that satisfy the predicate
    distinct Returns a sequence containing only distinct elements (first occurrence wins)
    distinctBy Returns a sequence containing only elements with distinct keys as computed by selector
    drop Returns a sequence that skips the first num elements
    dropWhile Returns a sequence that skips elements from the start while the predicate holds
    elementAt Returns the element at the given zero-based index, or undefined if the index is out of bounds
    elementAtOrElse Returns the element at the given zero-based index, or the result of defaultValue if the index is out of bounds
    every Determines whether all the members of this iterator satisfy the specified test
    filter Returns a sequence containing only the elements that satisfy the predicate
    filterKeys Returns a sequence containing only the [key, value] pairs whose key satisfies the predicate
    filterNot Returns a sequence containing only the elements that do not satisfy the predicate
    filterNotNull Returns a sequence with all null and undefined elements removed
    filterValues Returns a sequence containing only the [key, value] pairs whose value satisfies the predicate
    find Returns the first element matching the predicate, or undefined if none match
    first Returns the first element matching the predicate, or undefined if none match
    flatMap Maps each element to an iterable and flattens the results into a single sequence
    flatten Flattens a sequence of iterables into a single sequence
    fold Accumulates a value by applying operation left-to-right, starting from initial
    forEach Performs the specified action for each element in the iterator
    groupBy Groups elements into a Map by the key returned by keySelector
    indexOf Returns the zero-based index of the first occurrence of element (using ===), or -1 if it is not found
    indexOfFirst Returns the zero-based index of the first element matching the predicate, or -1 if none match
    indexOfLast Returns the zero-based index of the last element matching the predicate, or -1 if none match
    isEmpty Returns true if the sequence contains no elements
    isNotEmpty Returns true if the sequence contains at least one element
    joinToString Joins all elements into a single string
    last Returns the last element matching the predicate, or undefined if none match
    map Returns a sequence where each element is transformed by transform
    mapKeys Returns a sequence of [key, value] pairs where each key is transformed by transform
    mapNotNull Returns a sequence of transformed elements, skipping any null or undefined results
    mapValues Returns a sequence of [key, value] pairs where each value is transformed by transform
    max Returns the maximum element using the natural > ordering, or undefined if the sequence is empty
    maxBy Returns the element for which selector returns the largest value, or undefined if the sequence is empty
    maxWith Returns the maximum element according to the given compare function, or undefined if the sequence is empty
    min Returns the minimum element using the natural < ordering, or undefined if the sequence is empty
    minBy Returns the element for which selector returns the smallest value, or undefined if the sequence is empty
    minus Returns a sequence with the given element(s) excluded
    minWith Returns the minimum element according to the given compare function, or undefined if the sequence is empty
    none Returns true if no element satisfies the predicate
    onEach Performs the given action on each element and returns the same sequence unchanged
    partition Splits the sequence into two arrays: the first contains elements that satisfy the predicate, the second contains the rest
    plus Returns a sequence that contains all elements of this sequence followed by the given element or all elements of the given iterable
    reduce Calls the specified callback function for all the elements in this iterator
    reverse Returns a new sequence with elements in reverse order
    scan Returns a sequence of running accumulator values, starting with initial
    single Returns the single element matching the predicate, or undefined if there is no match or more than one match
    some Returns true if any element satisfies the predicate
    sorted Returns a new sequence with elements sorted in ascending order using natural ordering
    sortedBy Returns a new sequence sorted in ascending order by the key returned by selector
    sortedDescending Returns a new sequence with elements sorted in descending order using natural ordering
    sortedDescendingBy Returns a new sequence sorted in descending order by the key returned by selector
    sortedWith Returns a new sequence sorted using the given comparator
    sum Returns the sum of all elements in a numeric sequence
    sumBy Returns the sum of the values returned by selector for each element
    take Returns a sequence containing the first num elements
    takeWhile Returns a sequence of elements taken from the start while the predicate holds
    toArray Creates a new array from the values yielded by this iterator
    toMap Collects a sequence of [key, value] pairs into a Map
    toObject Collects a sequence of [key, value] pairs into a plain object
    toSet Collects all elements into a Set
    unzip Unzips a sequence of [A, B] pairs into a tuple of two arrays [A[], B[]]
    windowed Returns a sequence of sliding windows of the given size
    withIndex Returns a sequence of { index, value } pairs, where index is the zero-based position of each element
    zip Returns a sequence of pairs built by combining the elements of this sequence with elements from other
    zipWithNext Returns a sequence of pairs of each consecutive element with the next one
    from Creates a native iterator from an iterator or iterable object 
    pnpm build       # compile to dist/
    pnpm test        # run tests
    pnpm typecheck   # TypeScript type check
    pnpm dev         # watch mode

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