implementation of Normal and Circular Queue in JavaScript

Author: namitmalasi

CircularQueue.js

@@ -0,0 +1,44 @@
+class CircularQueue {
+  constructor(capacity) {
+    this.items = [];
+    this.head = 0;
+    this.tail = 0;
+    this.count = 0;
+    this.capacity = capacity;
+  }
+
+  isFull() {
+    return this.capacity === this.count;
+  }
+
+  //   adding the element to the queue
+  enqueue(element) {
+    if (this.isFull()) {
+      return new Error("Queue is Full");
+    }
+    this.items[this.tail] = element;
+    this.tail = (this.tail + 1) % this.capacity;
+    this.count++;
+  }
+
+  //   removing the element from the queue
+  dequeue() {
+    if (this.count === 0) return null;
+
+    let item = this.items[this.head];
+    this.head = (this.head + 1) % this.capacity;
+
+    this.count--;
+    return item;
+  }
+}
+
+const queue = new CircularQueue(5);
+
+queue.enqueue(10);
+queue.enqueue(20);
+queue.enqueue(30);
+queue.enqueue(40);
+queue.enqueue(50);
+queue.enqueue(60);
+console.log(queue);

Queue.js

@@ -0,0 +1,39 @@
+class Queue {
+  constructor() {
+    this.items = [];
+    this.head = 0;
+    this.tail = 0;
+    this.count = 0;
+  }
+
+  //   adding the element to the queue
+  enqueue(element) {
+    this.items[this.tail] = element;
+    this.tail++;
+    this.count++;
+  }
+
+  //   removing the element from the queue
+  dequeue() {
+    if (this.count === 0) return null;
+
+    let item = this.items[this.head];
+    this.head++;
+    if (this.head === this.tail) {
+      this.head = 0;
+      this.tail = 0;
+    }
+    this.count--;
+    return item;
+  }
+}
+
+const queue = new Queue();
+
+queue.enqueue(10);
+queue.enqueue(20);
+queue.enqueue(30);
+console.log(queue.dequeue());
+
+// One main drawback in using this type of queue is the memory wastage.
+// Circular queue can overcome this disadvantage.