Try it
function showFirstName(){
	var str = JSONfn.stringify(jsonfnObj);
	var objfn = JSONfn.parse(str);
	alert(objfn.firstName);
}
function showFullName(){
	var str = JSONfn.stringify(jsonfnObj);
	var objfn = JSONfn.parse(str);
	alert(objfn.getFullName());
}
function showLambdaGreeting(){
	var str = JSONfn.stringify(jsonfnObj);
	var objfn = JSONfn.parse(str);
	alert(objfn.greetLambda('Hello '));
}