Basic JavaScript Objects

/*var person = {
    firstname : "Thet",
    lastname : "Naing"
};

function tnwFun(){
    document.getElementById("demo").innerHTML = person.lastname;
}*/

var person = {
    firstname : "Thet",
    lastname : "Naing",
    fullname : function(){
        return person.firstname+ " " +person.lastname;
    }
}

function tnwFun(){
    document.getElementById("demo").innerHTML = person.fullname();
}