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/isSubset.md.
Install massaman

    isSubset es-toolkit

    Checks if one array is a subset of another array.

    const result = isSubset(superset, subset);

    Usage

    isSubset(superset, subset)

    Use isSubset when you want to check if all elements of one array are contained in another array. This is useful for verifying subset relationships or checking if permissions, features, tags, etc., are within the allowed range.

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

// Check subset in number arrays
const numbers = [1, 2, 3, 4, 5];
const subset = [2, 3, 4];
isSubset(numbers, subset);
// Returns: true

// Check subset in string arrays
const permissions = ['read', 'write', 'delete', 'admin'];
const userPermissions = ['read', 'write'];
isSubset(permissions, userPermissions);
// Returns: true

// When it's not a subset
const colors = ['red', 'blue', 'green'];
const invalidColors = ['red', 'yellow'];
isSubset(colors, invalidColors);
// Returns: false

    Special cases are also handled correctly.

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

// An empty array is always a subset
const anyArray = [1, 2, 3];
const emptyArray: number[] = [];
isSubset(anyArray, emptyArray);
// Returns: true

// The same array is a subset of itself
const same = ['a', 'b', 'c'];
isSubset(same, same);
// Returns: true

// Works correctly even with duplicate elements
const withDuplicates = [1, 2, 2, 3];
const duplicateSubset = [2, 2];
isSubset(withDuplicates, duplicateSubset);
// Returns: true

    Parameters

    supersetreadonly T[]required

    The superset array that may contain all elements of the subset.

    subsetreadonly T[]required

    The subset array to check if it's contained in the superset.

    Returns

    Returns true if all elements of the subset are contained in the superset, otherwise returns false.

    boolean
    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.