FuncType - v1.21.0
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    Interface CollectionOps<A, Self>

    Operations specific to collections (List, Set, etc.). These operations don't make sense for single-value containers.

    interface CollectionOps<out A extends Type, Self> {
        get head(): A | undefined;
        get headOption(): Option<A>;
        get init(): Self;
        get last(): A | undefined;
        get lastOption(): Option<A>;
        get tail(): Self;
        drop(n: number): Self;
        dropRight(n: number): Self;
        dropWhile(p: (a: A) => boolean): Self;
        every(p: (a: A) => boolean): boolean;
        flatten<B>(): Self;
        fold<B>(initial: B, fn: (acc: B, a: A) => B): B;
        take(n: number): Self;
        takeRight(n: number): Self;
        takeWhile(p: (a: A) => boolean): Self;
        toArray<B = A>(): B[];
    }

    Type Parameters

    • out A extends Type

      The element type

    • Self

      The collection type itself for proper return types

    Hierarchy (View Summary)

    Index
    head headOption init last lastOption tail
    drop dropRight dropWhile every flatten fold take takeRight takeWhile toArray
    • get head(): A | undefined

      Gets the first element of the collection.

      Returns A | undefined

    • get headOption(): Option<A>

      Gets the first element wrapped in Option.

      Returns Option<A>

    • get init(): Self

      Gets all elements except the last.

      Returns Self

    • get last(): A | undefined

      Gets the last element of the collection.

      Returns A | undefined

    • get lastOption(): Option<A>

      Gets the last element wrapped in Option.

      Returns Option<A>

    • get tail(): Self

      Gets all elements except the first.

      Returns Self

    • Drops the first n elements from the collection.

      Parameters

      • n: number

      Returns Self

    • Drops the last n elements from the collection.

      Parameters

      • n: number

      Returns Self

    • Drops elements from the start while the predicate is true.

      Parameters

      • p: (a: A) => boolean

      Returns Self

    • Tests whether every element satisfies the predicate. True for an empty collection. Stops at the first element that fails. The counterpart of exists.

      Parameters

      • p: (a: A) => boolean

      Returns boolean

      List([1, 2, 3]).every((x) => x > 0) // true
      List<number>([]).every((x) => x > 0) // true

    • Flattens a collection of collections into a single collection.

      Type Parameters

      • B

      Returns Self

    • Left-associative fold over all elements using an initial value and combining function. Unlike foldLeft (which is curried), this provides a convenient uncurried signature.

      Type Parameters

      • B

      Parameters

      • initial: B

        The initial accumulator value

      • fn: (acc: B, a: A) => B

        A function that combines the accumulator with each element

      Returns B

      The final accumulated value

      List([1, 2, 3]).fold(0, (acc, x) => acc + x) // 6

    • Takes the first n elements from the collection.

      Parameters

      • n: number

      Returns Self

    • Takes the last n elements from the collection.

      Parameters

      • n: number

      Returns Self

    • Takes elements from the start while the predicate is true.

      Parameters

      • p: (a: A) => boolean

      Returns Self

    • Converts the collection to an array.

      Type Parameters

      • B = A

      Returns B[]

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