Added CircularDoublyLinkedList.js alongwith it's test code

Data-Structures/Linked-List/CircularDoublyLinkedList.js

@@ -0,0 +1,138 @@
+// Explanation:- https://www.javatpoint.com/circular-doubly-linked-list
+
+class Node {
+  constructor (element) {
+    this.element = element
+    this.next = null
+    this.prev = null
+  }
+}
+
+class CircularDoublyLinkedList {
+  constructor () {
+    this.length = 0
+    this.head = null
+    this.tail = null
+  }
+
+  // Add new element
+  append (element) {
+    const node = new Node(element)
+
+    if (!this.head) {
+      this.head = node
+      this.tail = node
+      node.next = node // Circular reference
+      node.prev = node // Circular reference
+    } else {
+      node.prev = this.tail
+      node.next = this.head
+      this.tail.next = node
+      this.head.prev = node
+      this.tail = node
+    }
+
+    this.length++
+  }
+
+  // Insert element at a specific position
+  insert (position, element) {
+    if (position >= 0 && position <= this.length) {
+      const node = new Node(element)
+      let current = this.head
+      let previous = null
+      let index = 0
+
+      if (position === 0) {
+        node.next = current
+        node.prev = this.tail
+        this.head = node
+        current.prev = node
+        this.tail.next = node
+      } else {
+        while (index++ < position) {
+          previous = current
+          current = current.next
+        }
+        node.next = current
+        node.prev = previous
+        previous.next = node
+        current.prev = node
+
+        if (position === this.length) {
+          this.tail = node
+        }
+      }
+
+      this.length++
+      return true
+    } else {
+      return false
+    }
+  }
+
+  // Remove element at a specific position
+  removeAt (position) {
+    if (position >= 0 && position < this.length) {
+      let current = this.head
+      let previous = null
+      let index = 0
+
+      if (position === 0) {
+        this.head = current.next
+        this.head.prev = this.tail
+        this.tail.next = this.head
+        if (this.length === 1) {
+          this.tail = null
+        }
+      } else {
+        while (index++ < position) {
+          previous = current
+          current = current.next
+        }
+        previous.next = current.next
+        current.next.prev = previous
+
+        if (position === this.length - 1) {
+          this.tail = previous
+        }
+      }
+
+      this.length--
+      return current.element
+    } else {
+      return null
+    }
+  }
+
+  // Print the list
+  print () {
+    const elements = []
+    let currentNode = this.head
+    if (!currentNode) return
+    do {
+      elements.push(currentNode.element)
+      currentNode = currentNode.next
+    } while (currentNode !== this.head)
+    console.log(elements.join(' <-> '))
+  }
+
+  // Convert the list to a string
+  toString () {
+    const elements = []
+    let currentNode = this.head
+    if (!currentNode) return ''
+    do {
+      elements.push(currentNode.element)
+      currentNode = currentNode.next
+    } while (currentNode !== this.head)
+    return elements.join(' <-> ')
+  }
+
+  // Check if the list is empty
+  isEmpty () {
+    return this.length === 0
+  }
+}
+
+export { CircularDoublyLinkedList }

Data-Structures/Linked-List/test/CircularDoublyLinkedList.test.js

@@ -0,0 +1,55 @@
+import { CircularDoublyLinkedList } from '../CircularDoublyLinkedList' // Adjust the import path as needed
+
+describe('CircularDoublyLinkedList', () => {
+  it('Check append', () => {
+    const list = new CircularDoublyLinkedList()
+
+    list.append(1)
+    expect(list.toString()).toEqual('1')
+
+    list.append(2)
+    expect(list.toString()).toEqual('1 <-> 2')
+  })
+
+  it('Check insert', () => {
+    const list = new CircularDoublyLinkedList()
+
+    list.insert(0, 1)
+    expect(list.toString()).toEqual('1')
+
+    list.insert(1, 20)
+    expect(list.toString()).toEqual('1 <-> 20')
+  })
+
+  it('Check removeAt', () => {
+    const list = new CircularDoublyLinkedList()
+
+    list.append(10)
+    list.append(40)
+    list.append(30)
+
+    list.removeAt(0)
+    expect(list.toString()).toEqual('40 <-> 30')
+
+    list.removeAt(1)
+    expect(list.toString()).toEqual('40')
+  })
+
+  it('Check print', () => {
+    const list = new CircularDoublyLinkedList()
+
+    list.append(20)
+    expect(() => {
+      list.print()
+    }).not.toThrow()
+  })
+
+  it('Check isEmpty', () => {
+    const list = new CircularDoublyLinkedList()
+
+    expect(list.isEmpty()).toEqual(true)
+
+    list.append('Hello')
+    expect(list.isEmpty()).toEqual(false)
+  })
+})