Get the non-unique items in an array.
npm install array-non-uniq
const arrayNonUniq = require("array-non-uniq");
arrayNonUniq([1, 1, 2, 3, 3]);
//=> [1, 3]
arrayNonUniq(["foo", "foo", "bar", "foo"]);
//=> ['foo']
Type: array
The array to process.