Define A Constant In A Virtual Class

How is it possible to define a constant in a virtual class?

E.g. I wrote the following code

tml = {
sayHello : function()
{
alert('hello');
}}

now if I want to add a constant into tml virtual class, what I need to
do?

I tried something like

tml = {
const1 : Integer = 0,
sayHello : function()

or

tml = {
const1 : function(){return 0;},
sayHello : function()

in both case, trying to get - inside tml object - the value of
const1 ... it results in a Object value and not the Integer value I
need.