Mine

		function my_class(arg)
		{
			this.property = arg;
			this.setPropertyValue = my_func;
		}
		
		function my_func(val)
		{
			this.property = val;
		}
		
		var my_obj = new my_class("this is my property value");
		alert(my_obj.property);
		
		my_obj.setPropertyValue("this is the new property value");
		alert(my_obj.property);