diff --git a/javascript/3208-alternating-groups-ii.js b/javascript/3208-alternating-groups-ii.js
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+++ b/javascript/3208-alternating-groups-ii.js
@@ -0,0 +1,36 @@
+/**
+ * Sliding Window
+ * Time O(n) | Space O(n)
+ * https://leetcode.com/problems/alternating-groups-ii
+ * @param {number[]} colors
+ * @param {number} k
+ * @return {number}
+ */
+var numberOfAlternatingGroups = function(colors, k) {
+    
+    colors = [...colors, ...colors];
+    let left = 0;
+    let ptr = 0;
+    let count = 0;
+
+    while (left < colors.length/2) {
+
+        if ((ptr - left) + 1 === k) {
+            count++;
+            left++;
+            ptr++;
+
+            if (colors[ptr] === colors[ptr-1]) {
+                left = ptr;
+            }
+            continue;
+        }
+
+        ptr++
+        if (colors[ptr] === colors[ptr-1]) {
+            left = ptr;
+        } 
+    }
+
+    return count;
+};