30-seconds-of-code/snippets/hasDuplicates.md

title, tags, expertise, firstSeen, lastUpdated

title	tags	expertise	firstSeen	lastUpdated
Check if array has duplicates	array	beginner	2020-10-22T20:23:09+03:00	2020-10-22T20:23:09+03:00

Checks if there are duplicate values in a flat array.

• Use Set to get the unique values in the array.
• Use Set.prototype.size and Array.prototype.length to check if the count of the unique values is the same as elements in the original array.

const hasDuplicates = arr => new Set(arr).size !== arr.length;

hasDuplicates([0, 1, 1, 2]); // true
hasDuplicates([0, 1, 2, 3]); // false