application.alert("msg")

I have created a button and two drop downs with values populated. all the elements are in popup screen. i have to proceed only if both the values are selected, if not selected i want a pop up with a message.

In on click event i have written a logic.

if (dropdown1.getselectedvalue() == '' )

{

application.alert("dropdown 1 has no value");

}

else if (dropdown2.getselectedvalue() == '' )

{

application.alert("dropdown 2 has no value");

}

else {

some statements;

}

when i run the report in local mode the alert message is popping up

when i run the report on BI platform the alert message is not popping up.

WHY? And how can i achieve the popup of alert message.