Create new linked list from two given linked list with greater element at each node

<script>
// javascript program to create a new linked list 
// from two given linked list 
// of the same size with 
// the greater element among the two at each node 

    // Representation of node
class Node {
    constructor(val) {
        this.data = val;
        this.next = null;
    }
}
    // Function to insert node in a linked list
    function insert( root , item) {
        var ptr, temp;
        temp = new Node();
        temp.data = item;
        temp.next = null;

        if (root == null)
            root = temp;
        else {
            ptr = root;
            while (ptr.next != null)
                ptr = ptr.next;

            ptr.next = temp;
        }
        return root;
    }

    // Function which returns new linked list
    function newList( root1,  root2) {
        var ptr1 = root1, ptr2 = root2, ptr;
        var root = null, temp;

        while (ptr1 != null) {
            temp = new Node();
            temp.next = null;

            // Compare for greater node
            if (ptr1.data < ptr2.data)
                temp.data = ptr2.data;
            else
                temp.data = ptr1.data;

            if (root == null)
                root = temp;
            else {
                ptr = root;
                while (ptr.next != null)
                    ptr = ptr.next;

                ptr.next = temp;
            }
            ptr1 = ptr1.next;
            ptr2 = ptr2.next;
        }
        return root;
    }

    function display( root) {
        while (root != null) {
            document.write(root.data + "->");
            root = root.next;
        }
        document.write("<br/>");
    }

    // Driver code
    
         root1 = null, root2 = null, root = null;

        // First linked list
        root1 = insert(root1, 5);
        root1 = insert(root1, 2);
        root1 = insert(root1, 3);
        root1 = insert(root1, 8);

        document.write("First List: ");
        display(root1);

        // Second linked list
        root2 = insert(root2, 1);
        root2 = insert(root2, 7);
        root2 = insert(root2, 4);
        root2 = insert(root2, 5);

        document.write("Second List: ");
        display(root2);

        root = newList(root1, root2);
        document.write("New List: ");
        display(root);

// This code is contributed by gauravrajput1 
</script>