Move first element to end of a given Linked List

<script>

// JavaScript program to move first element
// to end in a given linked list 

/* A linked list node */
class Node 
{
    constructor()
    {
        this.data = 0;
        this.next = null;
    }
}

/* We are using a double pointer head_ref
here because we change head of the linked
list inside this function.*/
function moveToEnd(head_ref)
{
    
    /* If linked list is empty, or it contains
    only one node, then nothing needs to be
    done, simply return */
    if (head_ref == null || head_ref.next == null)
        return null;
    
    /* Initialize first and last pointers */
    var first = head_ref;
    var last = head_ref;
    
    /*After this loop last contains address
    of last node in Linked List */
    while (last.next != null) 
    {
        last = last.next;
    }
    
    /* Change the head pointer to point
    to second node now */
    head_ref = first.next;
    
    /* Set the next of first as null */
    first.next = null;
    
    /* Set the next of last as first */
    last.next = first;
    return head_ref;
}

/* UTILITY FUNCTIONS */
/* Function to add a node at the beginning
of Linked List */
function push(head_ref, new_data) 
{
    var new_node = new Node();
    new_node.data = new_data;
    new_node.next = head_ref;
    head_ref = new_node;
    return head_ref;
}

// Function to print nodes in 
// a given linked list 
function printList(node) 
{
    while (node != null) 
    {
        document.write(node.data + " ");
        node = node.next;
    }
}

// Driver code 
var start = null;

// The constructed linked list is:
// 1.2.3.4.5 
start = push(start, 5);
start = push(start, 4);
start = push(start, 3);
start = push(start, 2);
start = push(start, 1);

document.write("Linked list before " + 
               "moving first to end<br>");
printList(start);
start = moveToEnd(start);

document.write("<br> Linked list after moving " + 
               "first to end<br>");
printList(start);

// This code is contributed by rdtank

</script>

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

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

  insert(data) {
    let new_node = new Node(data);
    if (this.head == null) {
      this.head = new_node;
    } else {
      let current_node = this.head;
      while (current_node.next != null) {
        current_node = current_node.next;
      }
      current_node.next = new_node;
    }
  }

  display() {
    let current_node = this.head;
    while (current_node != null) {
      console.log(current_node.data + " ");
      current_node = current_node.next;
    }
    console.log();
  }

  move_first_to_end() {
    if (this.head == null || this.head.next == null) {
      return this.head;
    }

    let old_head = this.head;
    this.head = this.head.next;

    let current_node = this.head;
    while (current_node.next != null) {
      current_node = current_node.next;
    }

    current_node.next = old_head;
    old_head.next = null;

    return this.head;
  }
}

let linked_list = new LinkedList();
linked_list.insert(1);
linked_list.insert(2);
linked_list.insert(3);
linked_list.insert(4);
linked_list.insert(5);
console.log("Original Linked List: ");
linked_list.display();

linked_list.move_first_to_end();
console.log("Modified Linked List: ");
linked_list.display();

//This code is contributed by Akash Jha