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javascript/snippets/filter-non-unique.md

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+---
+title: Filter non-unique array values
+type: snippet
+tags: [array]
+cover: digital-nomad-10
+dateModified: 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.
+
+```js
+const filterNonUnique = arr =>
+  [...new Set(arr)].filter(i => arr.indexOf(i) === arr.lastIndexOf(i));
+```
+
+```js
+filterNonUnique([1, 2, 2, 3, 4, 4, 5]); // [1, 3, 5]
+```