FunctionisOneOf

  • isOneOf<T, ArrayElement>(element, array): element is ArrayElement

  • Returns whether array includes element.

    Logically this is the same as array.includes(element), but is typed differently to accommondate the scenario in which array contains literal-type elements. See is-one-of for details.

    Type Parameters

    • T

      The type of element.

    • ArrayElement

    Parameters

    • element: T

      The element to be determined whether it is included in array.

    • array: readonly ArrayElement[]

      The array to be determined whether it includes element.

    Returns element is ArrayElement

    Whether whether array includes element.

    See

    is-one-of

  • isOneOf<T, SetElement>(element, set): element is SetElement

  • Returns whether set includes element.

    Logically this is the same as set.has(element), but is typed differently to accommodate the scenario in which set contains literal-type elements. See is-one-of for details.

    Type Parameters

    • T

      The type of element.

    • SetElement

    Parameters

    • element: T

      The element to be determined whether it is included in set.

    • set: Readonly<Set<SetElement>>

      The set to be determined whether it includes element.

    Returns element is SetElement

    Whether whether set includes element.

    See

    is-one-of

  • isOneOf<T, Element>(element, collection): element is Element

  • A catch-all overload of the other two overloads. Check out the other two overloads for details.

    This overload addresses the edge case in which collection may be either a Array or Set, and is expected to be used rarely.

    Type Parameters

    • T
    • Element

    Parameters

    Returns element is Element

    Example

    for (const collection of [
      ["apple", "orange"] as const,
      new Set(["green", "red"] as const),
    ]) {
      isOneOf("sky", collection);
      // collection is of type readonly ["apple", "orange"] | Set<"green" | "red">
    }

Settings

Member Visibility