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Check if an array is subset of other array

Written byPhuoc Nguyen
Created
10 May, 2020
Last updated
22 Oct, 2021
Category
Validator
Contributors
lupu60
r
JavaScript version
isSubset.js
// Check if `b` is subset of `a`
const isSubset = (a, b) => new Set(b).size === new Set(b.concat(a)).size;

// Or
const isSubset = (a, b) => b.join('|').includes(a.join('|'));
TypeScript version
isSubset.ts
const isSubset = <T,_>(a: T[], b: T[]): boolean => new Set(b).size === new Set(b.concat(a)).size;

// Or
const isSubset = <T,_>(a: T[], b: T[]): boolean => b.join('|').includes(a.join('|'));
Examples
examples.js
isSubset([1, 2], [1, 2, 3, 4]); // true
isSubset([1, 2, 5], [1, 2, 3, 4]); // false
isSubset([6], [1, 2, 3, 4]); // false
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