How can I check if an object exists?

**MartinSmith** · Apr 24th, 2002, 07:02 AM

I have a linked js file which I use in several pages, some of these contain a ListBox Called lstNav, Others don't. If I reference lstNav in the pages where it doesn't exist I obviously get an error.

I have tried Checking if (lstNav == null) but get a "lstNav is undefined" error,

Does anyone know a way to do this?

**punkpie_uk** · Apr 24th, 2002, 07:36 AM

Hi,

I use this to check if an object exists within in a form. It displays 'doesnt exist' but displays 'does exist' if I add <input type="text" name="object1"> to the form

Code:

<html>
<head>
<title>Untitled</title>
<script language="JavaScript" type="text/javascript">
<!--
function checkIfExists(){
  if (document.form1.object1){
     alert ('does exist');
  }else{
     alert ('doesnt exist');
  }
}
//-->
</script>

</head>
<body>
<p onclick="javascript:checkIfExists()">Test If Exists</p>
<form name="form1">

</form>
</body>
</html>

**MartinSmith** · Apr 24th, 2002, 08:30 AM

Thanks very much, you wouldn't believe how much time I wasted on that one!

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