Javascript linkedlist test

linkedlist.js

var LinkedList = function() {
    
    this.head = null;
    this.tail = null;
    
    var Node = function(data) {   
        this.data = data;
        this.next = null;      
    };
    
    this.push = function(data) {
        var tmpnode = new Node(data);
        if(this.head == null){
            // we have no head this must be first entry, make head
            this.head = tmpnode; 
        } else if(this.tail == null) {
            // we have no tail so lets make this node it
            this.tail = tmpnode;
            this.head.next = this.tail;
        } else {
            // we are adding to end 
            this.tail.next = tmpnode;
            this.tail = tmpnode;
        }
    };
    
    this.pop = function() {
        var currentnode = this.head;
        while(currentnode != null) {
            if(currentnode.next == this.tail) {
                this.tail = currentnode;
                currentnode.next = null;
            }
            currentnode = currentnode.next;
        }
    };
    
    this.debug = function() {
        var currentnode = this.head;
        while(currentnode != null) {
            console.log(currentnode.data);
            currentnode = currentnode.next;
        }
    };
    
};


var ll = new LinkedList();
ll.push("A");
ll.push("B");
ll.push("C");
ll.debug();
ll.pop();
ll.debug();