30-seconds-of-code/javascript/snippets/has-duplicates.md

title, type, tags, cover, dateModified

title	type	tags	cover	dateModified
Check if array has duplicates	snippet	array	umbrellas	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