diff --git a/javascript/621-Task-Scheduler.js b/javascript/621-Task-Scheduler.js
new file mode 100644
index 000000000..4e3ca1043
--- /dev/null
+++ b/javascript/621-Task-Scheduler.js
@@ -0,0 +1,31 @@
+/**
+ * @param {character[]} tasks
+ * @param {number} n
+ * @return {number}
+ */
+var leastInterval = function(tasks, n) {
+  
+    const charMap = new Map();
+    let maxCharCount = 0;
+    let maxChar = tasks[0];
+    
+    for (let char of tasks) {
+        charMap.set(char, (charMap.get(char) || 0) + 1);
+        if (charMap.get(char) > maxCharCount) {
+            maxCharCount = charMap.get(char);
+            maxChar = char;
+        }
+    }
+    
+    let idleCount = (maxCharCount - 1) * n;
+    
+    charMap.forEach((count, char) => {
+        // 'return' inside forEach() serve as 'continue'
+        if (char === maxChar) return;
+        if (count === maxCharCount) idleCount -= (count - 1);
+        else idleCount -= count;
+    });
+    
+    if (idleCount <= 0) return tasks.length;
+    return tasks.length + idleCount;
+};