For AI agents: the complete documentation index is available at /llms.txt, the full documentation bundle is available at /llms-full.txt, and this page is available as Markdown at /reference/array/union.md.
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    union es-toolkit

    Creates a new array containing all unique elements from two arrays.

    const unified = union(arr1, arr2);

    Usage

    union(arr1, arr2)

    Use union when you want to combine all elements from multiple arrays without duplicates. It merges two arrays and returns a new array with duplicate values removed.

    import { union } from 'es-toolkit/array';

// Get the union of number arrays.
const array1 = [1, 2, 3];
const array2 = [3, 4, 5];
union(array1, array2);
// Returns: [1, 2, 3, 4, 5]

// Get the union of string arrays.
const fruits1 = ['apple', 'banana'];
const fruits2 = ['banana', 'orange'];
union(fruits1, fruits2);
// Returns: ['apple', 'banana', 'orange']

    Elements from the first array come first, followed by unique elements from the second array.

    import { union } from 'es-toolkit/array';

const arr1 = [1, 2, 3];
const arr2 = [2, 3, 4, 5];
union(arr1, arr2);
// Returns: [1, 2, 3, 4, 5]
// 1, 2, 3 are from arr1, 4, 5 are from arr2.

    Parameters

    arr1T[]required

    The first array to merge.

    arr2T[]required

    The second array to merge.

    Returns

    Returns a new array containing all unique elements from both arrays.

    T[]
    Source: es-toolkit

    Re-exported verbatim from es-toolkit. Implementation, edge cases, and performance behavior are owned upstream. This page mirrors the documentation at the pinned version; the linked source is authoritative.