Check if a flat array has duplicate values
Written byPhuoc Nguyen
Created
25 Feb, 2021
Last updated
26 Jan, 2022
Category
Validator
JavaScript version
hasDuplicateValues.js
const hasDuplicateValues = (arr) => new Set(arr).size !== arr.length;
// Or
const hasDuplicateValues = (arr) => arr.some((item, index, arr) => arr.indexOf(item) !== index);TypeScript version
hasDuplicateValues.ts
const hasDuplicateValues = <T,_>(arr: T[]): boolean => new Set(arr).size !== arr.length;
// Or
const hasDuplicateValues = <T,_>(arr: T[]): boolean => arr.some((item, index, arr) => arr.indexOf(item) !== index);Examples
examples.js
hasDuplicateValues(['h', 'e', 'l', 'l', 'o']); // true
hasDuplicateValues(['w', 'o', 'r', 'd']); // false
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Phước Nguyễn