Reverse alternate K nodes in a Singly Linked List - Iterative Solution

<script>
// javascript implementation of the approach    // Link list node
class Node {
    constructor(val) {
        this.data = val;
        this.next = null;
    }
}

    var head;

    /*
     * Function to reverse alternate k nodes and return the pointer to the new head
     * node
     */
    function kAltReverse(head , k) {
var prev = null;
var curr = head;
var temp = null;
var tail = null;
var newHead = null;
var join = null;
        var t = 0;

        // Traverse till the end of the linked list
        while (curr != null) {
            t = k;
            join = curr;
            prev = null;

            /*
             * Reverse alternative group of k nodes // of the given linked list
             */
            while (curr != null && t-- > 0) {
                temp = curr.next;
                curr.next = prev;
                prev = curr;
                curr = temp;
            }

            // Sets the new head of the input list
            if (newHead == null)
                newHead = prev;

            /*
             * Tail pointer keeps track of the last node of the k-reversed linked list. The
             * tail pointer is then joined with the first node of the next k-nodes of the
             * linked list
             */
            if (tail != null)
                tail.next = prev;

            tail = join;
            tail.next = curr;

            t = k;

            /*
             * Traverse through the next k nodes which will not be reversed
             */
            while (curr != null && t-- > 0) {
                prev = curr;
                curr = curr.next;
            }

            /*
             * Tail pointer keeps track of the last node of the k nodes traversed above
             */
            tail = prev;
        }

        // newHead is new head of the modified list
        return newHead;
    }

    // Function to insert a node at
    // the head of the linked list
    function push(head_ref , new_data) {
        /* allocate node */
var new_node = new Node();

        /* put in the data */
        new_node.data = new_data;

        /* link the old list of the new node */
        new_node.next = head_ref;

        /* move the head to point to the new node */
        head_ref = new_node;
        head = head_ref;
    }

    // Function to print the linked list
    function printList(node) {
        var count = 0;
        while (node != null) {
            document.write(node.data + " ");
            node = node.next;
            count++;
        }
    }

    // Driver code
    
        // Start with the empty list
        head = null;
        var i;

        // Create a list 1->2->3->4->...->10
        for (i = 10; i > 0; i--)
            push(head, i);

        var k = 3;

        document.write("Given linked list <br/>");
        printList(head);
        head = kAltReverse(head, k);

        document.write("<br/>Modified Linked list <br/>");
        printList(head);

// This code contributed by gauravrajput1 
</script>