Is it possible to have same script for Android and iOS apps?

If your flow is same for both iOS and Android then the best option would be like below,

function test()
{
testiOSLogin(Aliases.iOS.txtUserName,Aliases.iOS.txtPWD,Aliases.iOS.btnLogin,v_username,v_password);
testAndriodLogin(Aliases.Andriod.txtUserName,Aliases.Andriod.txtPWD,Aliases.Andriod.btnLogin,v_username,v_password);
}

//common function for login
function loginApp(obj_usrName,obj_passWord,objLoginButton,txt_userName,txt_Password)
{
           enterFiled(obj_usrName,txt_userName);      
           enterFiled(obj_passWord,txt_Password);
           
           if(objLoginButton.Exists)
           {
                  objLoginButton.Click();
           }
           
           //do the necessary check to know the login succesful and return true
           return true;
}

//common function for entering
function enterFiled(objecttoEnter,value)
{
      if(objecttoEnter.Exists)
     {
             objecttoEnter.Keys(value);
     }
}