const filterNonUnique = arr => arr.filter(i => arr.indexOf(i) === arr.lastIndexOf(i)); filterNonUnique([1, 2, 2, 3, 4, 4, 5]); // [1, 3, 5]
const filterNonUnique = arr => arr.filter(i => arr.indexOf(i) === arr.lastIndexOf(i)); filterNonUnique([1, 2, 2, 3, 4, 4, 5]); // [1, 3, 5]