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2025-11-28 19:45:44 -07:00

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TypeScript

/**
* Splits an array into two groups based on a predicate function.
*
* This function takes an array and a predicate function. It returns a tuple of two arrays:
* the first array contains elements for which the predicate function returns true, and
* the second array contains elements for which the predicate function returns false.
*
* @template T - The type of elements in the array.
* @template {T} U - The type being filtered for.
* @param {T[]} arr - The array to partition.
* @param {(value: T) => value is U} isInTruthy - A type guard that determines whether an
* element should be placed in the truthy array. The function is called with each element
* of the array.
* @returns {[U[], Exclude<T, U>[]]} A tuple containing two arrays: the first array contains elements for
* which the predicate returned true, and the second array contains elements for which the
* predicate returned false.
*
* @example
* const array = [1, 2, 3, 4] as const;
* const isEven = (x: number): x is 2 | 4 => x % 2 === 0;
* const [even, odd]: [(2 | 4)[], (2 | 4)[]] = partition(array, isEven);
* // even will be [2, 4], and odd will be [1, 3]
*/
declare function partition<T, U extends T>(arr: readonly T[], isInTruthy: (value: T) => value is U): [truthy: U[], falsy: Array<Exclude<T, U>>];
/**
* Splits an array into two groups based on a predicate function.
*
* This function takes an array and a predicate function. It returns a tuple of two arrays:
* the first array contains elements for which the predicate function returns true, and
* the second array contains elements for which the predicate function returns false.
*
* @template T - The type of elements in the array.
* @param {T[]} arr - The array to partition.
* @param {(value: T) => boolean} isInTruthy - A predicate function that determines
* whether an element should be placed in the truthy array. The function is called with each
* element of the array.
* @returns {[T[], T[]]} A tuple containing two arrays: the first array contains elements for
* which the predicate returned true, and the second array contains elements for which the
* predicate returned false.
*
* @example
* const array = [1, 2, 3, 4, 5];
* const isEven = x => x % 2 === 0;
* const [even, odd] = partition(array, isEven);
* // even will be [2, 4], and odd will be [1, 3, 5]
*/
declare function partition<T>(arr: readonly T[], isInTruthy: (value: T) => boolean): [truthy: T[], falsy: T[]];
export { partition };