Insert a node after the n-th node from the end

<script>

// JavaScript implementation to
// insert a node after 
// the n-th node from the end 

    // structure of a node
     class Node {
            constructor() {
                this.data = 0;
                this.next = null;
            }
        }

    // function to get a new node
    function getNode(data) {
        // allocate memory for the node
var newNode = new Node();

        // put in the data
        newNode.data = data;
        newNode.next = null;
        return newNode;
    }

    // function to insert a node after the
    // nth node from the end
    function insertAfterNthNode(head , n , x) {
        // if list is empty
        if (head == null)
            return;

        // get a new node for the value 'x'
var newNode = getNode(x);
var ptr = head;
        var len = 0, i;

        // find length of the list, i.e, the
        // number of nodes in the list
        while (ptr != null) {
            len++;
            ptr = ptr.next;
        }

        // traverse up to the nth node from the end
        ptr = head;
        for (i = 1; i <= (len - n); i++)
            ptr = ptr.next;

        // insert the 'newNode' by making the
        // necessary adjustment in the links
        newNode.next = ptr.next;
        ptr.next = newNode;
    }

    // function to print the list
    function printList(head) {
        while (head != null) {
            document.write(head.data + " ");
            head = head.next;
        }
    }

    // Driver code
    
        // Creating list 1->3->4->5
var head = getNode(1);
        head.next = getNode(3);
        head.next.next = getNode(4);
        head.next.next.next = getNode(5);

        var n = 4, x = 2;

        document.write("Original Linked List: ");
        printList(head);

        insertAfterNthNode(head, n, x);
        document.write();
        document.write("<br/>Linked List After Insertion: ");
        printList(head);

// This code contributed by gauravrajput1

</script>

<script>

      // JavaScript implementation to
      // insert a node after the
      // nth node from the end
      // structure of a node
      class Node {
        constructor() {
          this.data = 0;
          this.next = null;
        }
      }

      // function to get a new node
      function getNode(data) {
        // allocate memory for the node
        var newNode = new Node();

        // put in the data
        newNode.data = data;
        newNode.next = null;
        return newNode;
      }

      // function to insert a node after
      // the nth node from the end
      function insertAfterNthNode(head, n, x) {
        // if list is empty
        if (head == null) return;

        // get a new node for the value 'x'
        var newNode = getNode(x);

        // Initializing the slow
        // and fast pointers
        var slow_ptr = head;
        var fast_ptr = head;

        // move 'fast_ptr' to point to the
        // nth node from the beginning
        for (var i = 1; i <= n - 1; i++) 
        fast_ptr = fast_ptr.next;

        // iterate until 'fast_ptr' points
        // to the last node
        while (fast_ptr.next != null) {
          // move both the pointers to the
          // respective next nodes
          slow_ptr = slow_ptr.next;
          fast_ptr = fast_ptr.next;
        }

        // insert the 'newNode' by making the
        // necessary adjustment in the links
        newNode.next = slow_ptr.next;
        slow_ptr.next = newNode;
      }

      // function to print the list
      function printList(head) {
        while (head != null) {
          document.write(head.data + " ");
          head = head.next;
        }
      }

      // Driver code
      // Creating list 1->3->4->5
      var head = getNode(1);
      head.next = getNode(3);
      head.next.next = getNode(4);
      head.next.next.next = getNode(5);

      var n = 4,
        x = 2;
      document.write("Original Linked List: ");
      printList(head);

      insertAfterNthNode(head, n, x);
      document.write("<br>");
      document.write("Linked List After Insertion:");
      printList(head);
      
</script>

    // JavaScript implementation to insert a node after the
    // nth node from the end

    // structure of a node
    class Node {
        constructor(data) {
            this.data = data;
            this.next = null;
        }
    }

    let n;

    // function to insert a node after the
    // nth node from the end
    function insertAfterNthNode(head, x) {
        // base case
        if (head == null) return;

        // recursively traverse till the last node
        insertAfterNthNode(head.next, x);

        // condition to insert the node after nth node from end
        if (--n == 0) {
            // create a node with the given value
            let temp = new Node(x);

            // update the next pointer to point to the next node in the list
            temp.next = head.next;

            // make sure head points to the newly inserted node
            head.next = temp;
        }
    }

    // function to print the list
    function printList(head) {
        let current = head;
        while (current != null) {
            console.log(current.data + " ");
            current = current.next;
        }
        console.log("<br>");
    }

    // create a linked list: 1 -> 3 -> 4 -> 5
    let head = new Node(1);
    head.next = new Node(3);
    head.next.next = new Node(4);
    head.next.next.next = new Node(5);

    n = 4;
    let x = 2;

    console.log("Original Linked List: ");
    printList(head);

    insertAfterNthNode(head, x);
    console.log("\nLinked List After Insertion: ");
    printList(head);
    
    // This code is contributed by lokeshmvs21.