javascript: check if file input is undefined

[sde]

I need to check if a file input box is undefined, but I can not get this to work.

If I alert(document.lform.logoimage.value); , it pops up: "undefined"

So I have tried to evaluate that field to "undefined" and "", and neither work.

so how can I check if a file is not there? i only want this confirmation box to pop up if the user has chosen a file to upload. ( there are other text elements on the form )

<Script language="JavaScript">
<!--
function verifyLogo(){
  
  if( document.lform.logoimage.value !=  "" ){
    var c = confirm("Are you sure you want to replace the logo image?\nThe current image will be deleted.");
    if( c ){
      return true ;
    }else{
      return false ;
    }
  }
  return true ;
}
-->
</script>

[idx]

I'll have to check, but you might be out of luck. The file upload boxes are pretty limited JS-wise due to obvious security issues, but it seems like you could at least check the value on the client-side..

-r

[idx]

hrm.. works for me. eg:

<script>
<!--
  function check_form(form) {

     if (form.foo.value == "") {
        alert("foo is required!");
        form.foo.focus();
        return false;
     }

     return true;
  }

//-->
</script>

<form name="me" action="<?=$_SERVER['PHP_SELF']?>" method="POST" onsubmit="return check_form(this);">

<input type="file" name="foo">
<input type="submit">
</form>

[sde]

cool thanks! .. i wasn't sending it the form as the argument.