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snippets/js/s/has-duplicates.md

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+---
+title: Check if array has duplicates
+type: snippet
+language: javascript
+tags: [array]
+cover: umbrellas
+dateModified: 2020-10-22T20:23:09+03:00
+---
+
+Checks if there are duplicate values in a flat array.
+
+- Use `Set` to get the unique values in the array.
+- Use `Set.prototype.size` and `Array.prototype.length` to check if the count of the unique values is the same as elements in the original array.
+
+```js
+const hasDuplicates = arr => new Set(arr).size !== arr.length;
+```
+
+```js
+hasDuplicates([0, 1, 1, 2]); // true
+hasDuplicates([0, 1, 2, 3]); // false
+```