30-seconds-of-code/js/s/filter-non-unique.md

title, type, language, tags, cover, dateModified

title	type	language	tags	cover	dateModified
Filter non-unique array values	snippet	javascript	array	digital-nomad-10	2020-11-02T19:40:45+02:00

Creates an array with the non-unique values filtered out.

• Use the Set constructor and the spread operator (...) to create an array of the unique values in arr.
• Use Array.prototype.filter() to create an array containing only the unique values.

const filterNonUnique = arr =>
  [...new Set(arr)].filter(i => arr.indexOf(i) === arr.lastIndexOf(i));

filterNonUnique([1, 2, 2, 3, 4, 4, 5]); // [1, 3, 5]