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snippets/js/s/all-unique.md

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+---
+title: Check if all array elements are unique
+type: snippet
+language: javascript
+tags: [array]
+cover: jars-on-shelf
+dateModified: 2021-01-08T00:23:44+02:00
+---
+
+Checks if all elements in an array are unique.
+
+- Create a new `Set` from the mapped values to keep only unique occurrences.
+- Use `Array.prototype.length` and `Set.prototype.size` to compare the length of the unique values to the original array.
+
+```js
+const allUnique = arr => arr.length === new Set(arr).size;
+```
+
+```js
+allUnique([1, 2, 3, 4]); // true
+allUnique([1, 1, 2, 3]); // false
+```