Function isUndefined

  • isUndefined<T>(x: undefined | T): x is undefined

    Verifies that the given value is undefined. This especially helps with a .filter

    Type Parameters

    • T

    Parameters

    • x: undefined | T

    Returns x is undefined

    Example

    const values: (number | undefined)[] = [1, 2, undefined, 4];
    const undefinedValues: undefined[] = values.filter(isUndefined);
    // undefinedValues is now of type undefined[]

    See

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