Exit confirmation message

Question

I am working with creating documents, where the user enters with the information so that the document can be generated. I would like if the user had already written something in any of the fields and clicked to exit the page, an output confirmation message would appear on the screen. I read about other topics here and found out onbeforeunload of Javascript, however, I found nothing talking about how to make the message appear only if there is something in the fields. My code is like this:

<script language="JavaScript">
    window.onbeforeunload = confirmExit;
    function confirmExit(){
        if((document.getElementsByName("interessado").value != "")||
           (document.getElementsByName("assunto").value != "")||
           (document.getElementsByName("assinatura").value != "")){
                return "Deseja realmente sair?";
        }
    }

How can I create an output confirmation message only if there is some information in the text fields?

Answer 1

getElementsByName returns an array, so you need to check the index:

function confirmExit(){
    if( ( !document.getElementsByName("interessado")[0].value )||
        ( !document.getElementsByName("assunto")[0].value )||
        ( !document.getElementsByName("assinatura")[0].value )){
            return "Deseja realmente sair?";
    }      
}