es-toolkit/docs/reference/array/partition.md

partition

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.

Signature

function partition<T>(arr: T[], isInTruthy: (value: T) => boolean): [truthy: T[], falsy: T[]];

Parameters

• arr (T[]): The array to partition.
• isInTruthy ((value: T) => boolean): 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.

Examples

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]