Delete all the even nodes of a Circular Linked List

<script>
// javascript program to delete all prime 
// node from a Circular singly linked list     // Structure for a node
class Node {
    constructor() {
        this.data = 0;
        this.next = null;
    }
}

    // Function to insert a node at the beginning
    // of a Circular linked list
    function push(head_ref , data) {
var ptr1 = new Node();
var temp = head_ref;
        ptr1.data = data;
        ptr1.next = head_ref;

        // If linked list is not null then
        // set the next of last node
        if (head_ref != null) {
            while (temp.next != head_ref)
                temp = temp.next;
            temp.next = ptr1;
            return head_ref;
        } else
            ptr1.next = ptr1; // For the first node

        head_ref = ptr1;
        return head_ref;
    }

    // Delete the node if it is even
    function deleteNode(head_ref,  del) {
var temp = head_ref;
        // If node to be deleted is head node

        if (head_ref == del)
            head_ref = del.next;

        // traverse list till not found
        // delete node
        while (temp.next != del) {
            temp = temp.next;
        }

        // copy address of node
        temp.next = del.next;

        return head_ref;
    }

    // Function to delete all even nodes
    // from the singly circular linked list
    function deleteEvenNodes(head) {
var ptr = head;

var next;

        // traverse list till the end
        // if the node is even then delete it
        do {
            // if node is even
            if (ptr.data % 2 == 0)
                deleteNode(head, ptr);

            // point to next node
            next = ptr.next;
            ptr = next;
        } while (ptr != head);
        return head;
    }

    // Function to print nodes
    function printList(head) {
var temp = head;
        if (head != null) {
            do {
                document.write( temp.data+" ");
                temp = temp.next;
            } while (temp != head);
        }
    }

    // Driver code
    
        // Initialize lists as empty
var head = null;

        // Created linked list will be 57.11.2.56.12.61
        head = push(head, 61);
        head = push(head, 12);
        head = push(head, 56);
        head = push(head, 2);
        head = push(head, 11);
        head = push(head, 57);

        document.write("\nList after deletion : ");
        head = deleteEvenNodes(head);
        printList(head);

// This code contributed by umadevi9616
</script>