filterNonUnique javascript Code Snippet in 2025
arraybeginner
Last Updated: 20 October 2025
Creates an array with the non-unique values filtered out.
- Use
new Set()and the spread operator (...) to create an array of the unique values inarr. - 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]
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