Find out whether a node exists 2

kaeserea · Dec 27, 2004

Hello!

I usually get the values of form elements with the method getElementById("myId"). I have now a case where the form element maybe there or not. Thus I first need to find that out as to not receive an error like "element is null or not an object".

Does anybody know if there's a function like exists() isNode() or something like that?

Best regards
Eva

Shukusei · Dec 27, 2004

Couldn't you check the value of the node by putting it into a variable, and then testing whether it's null or not?

kaht · Dec 27, 2004

Hi kaeserea, using a try/catch clause will accomplish what you're looking to do. What I would suggest is saving the values from the form elements into variables, and if the form elements don't exist set the values to null instead. Try out this sample I typed up to help give you an idea of how to incorporate it into your application:

Code:

<html>
<head>
<script language=javascript>

function displayValue(str) {
   try {
      obj = document.getElementById(str);
   }
   catch(e) {
      obj = null;
   }
   if (obj == null) {
      alert("textbox does not exist");
   }
   else {
      alert("textbox value is:\n\n" + obj.value);
   }
}

</script>
</head>
<body>
<form name=blahForm>
<input type=text id=text1>Textbox1<br>
<input type=button value='display textbox1 value' onclick='displayValue("text1")'><br><br>
No textbox2 exists!!<br>
<input type=button value='display textbox2 value' onclick='displayValue("text2")'><br><br>
</form>
</body>
</html>

-kaht

adam0101 · Dec 27, 2004

getElementById should return null if it can't find the element. You should be able to do this:

Code:

obj = document.getElementById(str);
if(obj){
  alert('Object exists!');
}

Adam
"Computers make it easier to do a lot of things, but most of the things they make it easier to do don't need to be done." Andy Rooney.

kaeserea · Dec 27, 2004

Hello!

Thanx for all of your help. That's great to get three good answers. They work well.

Best wishes !
Eva

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Find out whether a node exists 2

kaeserea

Programmer

Shukusei

Programmer

kaht

Programmer

adam0101

Programmer

kaeserea

Programmer

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