允许未定义的变量作为null传递到Firebase

Is there a way to allow variables which are undefined to pass into Firebase as null? In my application I have a lot of cases where a variable might not be defined and it prevents the entire object model from being added into firebase. So I have to detect if each potential variable is defined and then set it to 0 if it isn't. It would be a lot easier if Firebase just accepted undefined variables as 0 or null.Is there a way to allow variables which are und