Create isDuplicates.md

snippets/isDuplicates.md

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+---
+title: isDuplicates
+tags: array,intermediate
+---
+
+Check if there's duplicate values in a flat array.
+
+- Convert original array into a Set.
+- The `.size()` returns the number of (unique) elements in a Set object.
+- Compare the lengths of the array and the Set.
+
+
+```js
+function isDuplicates(array) {
+  return new Set(array).size !== array.length
+}
+```
+
+```js
+isDuplicates([0,1,1,2]); // 'True'
+isDuplicates([0,1,2,3,]); // 'False'
+```