Implement doubly linked list

Author: gopinav

Diff for: linked-list-double.js

@@ -0,0 +1,100 @@
+class Node {
+  constructor(value) {
+    this.value = value;
+    this.prev = null;
+    this.next = null;
+  }
+}
+
+class DoublyLinkedList {
+  constructor() {
+    this.head = null;
+    this.tail = null;
+    this.size = 0;
+  }
+
+  isEmpty() {
+    return this.size === 0;
+  }
+
+  getSize() {
+    return this.size;
+  }
+
+  prepend(value) {
+    const node = new Node(value);
+    if (this.isEmpty()) {
+      this.head = node;
+      this.tail = node;
+    } else {
+      node.next = this.head;
+      this.head.prev = node;
+      this.head = node;
+    }
+    this.size++;
+  }
+
+  append(value) {
+    const node = new Node(value);
+    if (this.isEmpty()) {
+      this.head = node;
+      this.tail = node;
+    } else {
+      this.tail.next = node;
+      node.prev = this.tail;
+      this.tail = node;
+    }
+    this.size++;
+  }
+
+  removeFromFront() {
+    if (this.isEmpty()) {
+      return null;
+    }
+    const value = this.head.value;
+    this.head = this.head.next;
+    this.size--;
+    return value;
+  }
+
+  removeFromEnd() {
+    if (this.isEmpty()) {
+      return null;
+    }
+    const value = this.tail.value;
+    if (this.size === 1) {
+      this.head = null;
+      this.tail = null;
+    } else {
+      this.tail = this.tail.prev;
+      this.tail.next = null;
+    }
+    this.size--;
+    return value;
+  }
+
+  print() {
+    if (this.isEmpty()) {
+      console.log("List is empty");
+    } else {
+      let curr = this.head;
+      let list = "";
+      while (curr) {
+        list += `${curr.value}<->`;
+        curr = curr.next;
+      }
+      console.log(list);
+    }
+  }
+}
+
+const list = new DoublyLinkedList();
+list.append(1);
+list.append(2);
+list.append(3);
+list.prepend(0);
+list.print();
+list.removeFromEnd();
+list.print();
+list.removeFromFront();
+list.print();