function LinkedList(value, next) {
    this._value = value;
    this._next = next;
}
LinkedList.prototype.value = function() {
    if (arguments.length == 1)
        this._value = arguments[0];
    else
        return this._value;
}
LinkedList.prototype.next = function() {
    if (arguments.length == 1)
        this._next = arguments[0];
    else
        return this._next;
}

// convenience function to assist the creation of linked lists.
function createLinkedListFromArray(ary) {
    var head = new LinkedList(ary[0], null);
    var prev = head;
    for (var i = 1; i < ary.length; i++) {
        var node = new LinkedList(ary[i], null);
        prev.next(node);
        prev = node;
    }
    return head;
}

var head = createLinkedListFromArray([10,20,30,40]);