javascript - simple linked list traversal issue

Question

I have implemented a single linked list using javascript. Please find the code below:

class Node {
  constructor(data) {
    this.data = data;
    this.nextElement = null;
  }
}

class LinkedList {
  constructor() {
    this.head = null;
  }

  isEmpty() {
    return this.head === null;
  }

  insertAtHead(data) {
    const tempNode = new Node(data);
    tempNode.nextElement = this.head;
    this.head = tempNode;
  }

  traverse() {
    let current = this.head;
    while (current.nextElement != null) {
      console.log("node data", current.data);
      current = current.nextElement;
    }
  }

  insertAtTail(data) {
    const tempNode = new Node(data);
    if (this.head === null) {
      this.head = tempNode;
      return;
    }

    let currentNode = this.head;
    while (currentNode.nextElement != null) {
      currentNode = currentNode.nextElement;
    }

    currentNode.nextElement = tempNode;
  }
}

const linkedList = new LinkedList();
linkedList.insertAtTail(12);
linkedList.insertAtTail(23);
linkedList.insertAtTail(25);

linkedList.traverse();

But the traverse method never prints the last element. What am I missing here? The insertAtTail method looks correct though. Could anyone please let me know.

thanks

Answer 1

In the traverse, you need to check all nodes not until the next one is null.

so I just removed the .nextElement from the traverse and it works fine

class Node {
  constructor(data) {
    this.data = data;
    this.nextElement = null;
  }
}

class LinkedList {
  constructor() {
    this.head = null;
  }

  isEmpty() {
    return this.head === null;
  }

  insertAtHead(data) {
    const tempNode = new Node(data);
    tempNode.nextElement = this.head;
    this.head = tempNode;
  }

  traverse() {
    let current = this.head;
    while (current) { // Here
      console.log("node data", current.data);
      current = current.nextElement;
    }
  }

  insertAtTail(data) {
    const tempNode = new Node(data);
    if (this.head === null) {
      this.head = tempNode;
      return;
    }

    let currentNode = this.head;
    while (currentNode.nextElement != null) {
      currentNode = currentNode.nextElement;
    }

    currentNode.nextElement = tempNode;
  }
}

const linkedList = new LinkedList();
linkedList.insertAtTail(12);
linkedList.insertAtTail(23);
linkedList.insertAtTail(25);


linkedList.traverse();