JavaScript Exercises: Insert a new node at the end of a Doubly Linked List
JavaScript Data Structures: Exercise-7 with Solution
Write a JavaScript program to insert a new node at the end of a Doubly Linked List.
Sample Solution:
JavaScript Code:
// Define a class for creating nodes of a doubly linked list
class Node {
constructor(value) {
this.value = value; // Store the value of the node
this.next = null; // Pointer to the next node in the list, initially set to null
this.previous = null; // Pointer to the previous node in the list, initially set to null
}
}
// Define a class for creating a doubly linked list
class DoublyLinkedList {
constructor(value) {
// Initialize the head node with the given value and no next or previous node
this.head = {
value: value, // Store the value of the head node
next: null, // Pointer to the next node in the list, initially set to null
previous: null // Pointer to the previous node in the list, initially set to null
};
this.length = 0; // Initialize the length of the list to 0
this.tail = this.head; // Set the tail node to the head node initially
}
// Method to add a new node at the end of the list
add(newNode) {
// Check if the head is null, indicating an empty list
if (this.head === null) {
this.head = newNode; // Set the head to the new node
this.tail = newNode; // Set the tail to the new node
} else {
newNode.previous = this.tail; // Set the previous pointer of the new node to the current tail
this.tail.next = newNode; // Set the next pointer of the current tail to the new node
this.tail = newNode; // Update the tail to the new node
}
this.length++; // Increment the length of the list
}
// Method to insert a new node at a specified position in the list
insertAt(position, data) {
if (position < 0 || position > this.length) {
return false; // Return false if the position is invalid
}
var newNode = { // Create a new node with the given data
value: data,
next: null,
previous: null
};
if (this.length === 0) { // If the list is empty, set the head and tail to the new node
this.head = newNode;
this.tail = newNode;
} else if (position === 0) { // If inserting at the beginning, update the head
newNode.next = this.head;
this.head.previous = newNode;
this.head = newNode;
} else if (position === this.length) { // If inserting at the end, update the tail
this.tail.next = newNode;
newNode.previous = this.tail;
this.tail = newNode;
} else { // Otherwise, find the position and insert the new node
var current = this.head;
var index = 0;
while (index < position) {
current = current.next;
index++;
}
newNode.next = current;
newNode.previous = current.previous;
current.previous.next = newNode;
current.previous = newNode;
}
this.length++; // Increment the length of the list
return true; // Return true to indicate successful insertion
}
// Method to insert a new node at the last position in the list
insertLast(value) {
this.insertAt(this.length, value); // Call the insertAt method with the last position
}
// Method to print the values of the nodes in the list
printList() {
let current = this.head; // Start from the head of the list
let result = []; // Array to store the values of the nodes
while (current !== null) { // Iterate through the list until reaching the end
result.push(current.value); // Push the value of the current node to the array
current = current.next; // Move to the next node
}
console.log(result.join(' ')); // Log the values of the nodes separated by space
return this; // Return the DoublyLinkedList object for chaining
}
}
// Create a new instance of the DoublyLinkedList class
let numList = new DoublyLinkedList();
// Add nodes to the list
numList.add(new Node(2));
numList.add(new Node(3));
numList.add(new Node(4));
numList.add(new Node(5));
numList.add(new Node(6));
numList.add(new Node(7));
// Display the original doubly linked list
console.log("Original Doubly Linked List:");
numList.printList();
// Insert a new node at the last position with value 12
console.log("Insert at last position and value = 12");
numList.insertLast(12);
numList.printList();
// Insert another new node at the last position with value 14
console.log("Again insert at last position and value = 14");
numList.insertLast(14);
numList.printList();
Output:
"Original Doubly Linked Lists:" " 2 3 4 5 6 7" "Insert at last position and value = 12" " 2 3 4 5 6 7 12" "Again insert at last position and value = 14" " 2 3 4 5 6 7 12 14"
Flowchart:
![Flowchart: JavaScript Exercises: Insert a new node at the end of a Doubly Linked List.](https://www.w3resource.com/w3r_images/javascript-doubly-linked-list-exercise-flowchart-7.png)
Live Demo:
See the Pen javascript-doubly-linked-list-exercise-7 by w3resource (@w3resource) on CodePen.
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Linked List Previous:Insert a new node at the beginning of a Doubly Linked List.
Linked List Next: Get the value of a node at a given position in a Doubly Linked List.
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