The following code sends an alert to the browser if the user hasn't filled in all the required fields. Please note that it sends multiple messages on separate lines when the user "forgets" to fill in multiple fields.

function checkForm (f) {
  var alertMessage="" ;
  var checkStatus=true ;
  for (i=0;i<registeredFields.length;i++) {
    var field=registeredFields[i] ;
    if (1 == field.required) {
      if ("singleselect" == field.type) {
        var fieldValue=f.elements[field.name].value ;
        if ("Unspecified" == fieldValue || "" == fieldValue) {
          alertMessage += field.description+" is required\n" ;
          checkStatus=false ;
        }
      } else
      if ("multiselect" == field.type) {
        var selectedIndex=f.elements[field.name].selectedIndex ;
        if (-1 == selectedIndex) {
          alertMessage += "A valid "+field.description+" is required\n" ;
          checkStatus=false ;
        }
      } else
      if ("textinput" == field.type) {
        var fieldValue=f.elements[field.name].value ;
        if (0 == fieldValue.length) {
          alertMessage += field.description+" is required\n" ;
          checkStatus=false ;
        }
      }
    }
  }
  if (false == checkStatus) {
    alert (alertMessage) ;
  }
  return checkStatus ;
}

The problem is, when we simulate forgetting multiple items in Selenium test scripts, get_alert() only reports one of the messages rather than the three we expect.