Create Count Duplicate Elements.md

Author: cheatsheet1999

JS-Algo/Count Duplicate Elements.md

@@ -0,0 +1,23 @@
+<img width="520" alt="Screen Shot 2022-03-08 at 18 45 31" src="https://user-images.githubusercontent.com/37787994/157356147-149dbcaf-5084-4f59-83aa-9d9c9124f7e0.png">
+<img width="520" alt="Screen Shot 2022-03-08 at 18 45 42" src="https://user-images.githubusercontent.com/37787994/157356150-682279a5-5e8b-4474-a57a-48c6c28db7e0.png">
+
+```js
+function countDuplicate(numbers) {
+    // Write your code here
+    let counts = {};
+    let counter = 0;
+    numbers.forEach(function(x) {
+        counts[x] = (counts[x] || 0) + 1;
+    });
+    
+    for(let key in counts) {
+        if(counts[key] !== 1) {
+            counter++;
+        }
+    }
+    
+    return counter;
+    
+}
+
+```