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Weird radio button count error

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countdrak

countdrak

Programmer
Jun 20, 2003
358
US
I have a radio button

<input type="radio" name="shipadd" value="1" id="shipadd" />

When I do this -


alert(document.thisform.shipadd.length); I get my value undefined.

But when I have 2 radio buttons with the same name I get value as 2.

Why is this happening? Shouldn't the value with one radio button be 1.

Because the value is "undefined" a simple for loop doesn't work for me.

for (counter = 0; counter < document.thisform.shipadd.length; counter++)

Any help would be great.Thanks guys.
 
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Radio buttons that do not exist in pairs (i.e. only one radio button exists with a particular name) are not treated as an array of elements - and as such do not have length properties and trying to access that property will return null. So, you will have to modify your function to detect for this. Here's an example:
Code: 
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "[URL unfurl="true"]http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">[/URL]
<html xmlns="[URL unfurl="true"]http://www.w3.org/1999/xhtml">[/URL]
<head>
<title>title test</title>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" />
<script type="text/javascript">

window.onload = function () {

   alertValues(document.forms["theForm"].elements["radio1"]);
   alertValues(document.forms["theForm"].elements["radio2"]);
 
};

function alertValues(obj) {
   if (obj.length) {
      for (var i = 0; i < obj.length; i++) {
         alert(obj[i].value);
      }
   }
   else {
      alert(obj.value);
   }
}

</script>
<style type="text/css"></style>
</head>
<body>

<form id="theForm">
   <input type="radio" name="radio1" value="radio1-1" />
   
   <input type="radio" name="radio2" value="radio2-1" />
   <input type="radio" name="radio2" value="radio2-2" />
</form>

</body>
</html>

-kaht

Lisa, if you don't like your job you don't strike. You just go in every day and do it really half-assed. That's the American way. - Homer Simpson
 
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That's because [tt]document.thisform.shipadd[/tt] refers to a collection when there is more than one radio button with the same name, but when there is only one button it refers to only that button, not a collection. Use [tt]document.getElementsByName("myRadioGroup")[/tt] to always return a collection.

Adam
 
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I added a hidden field with the same name and it seemed to work. Is that a good fix?
 
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Is that a good fix?
Click to expand...

Not really. You're adding useless markup that serves no purpose to your page when you can solve the problem with 2 or 3 lines of javascript. Did you read my post above?

-kaht

Lisa, if you don't like your job you don't strike. You just go in every day and do it really half-assed. That's the American way. - Homer Simpson
 
Upvote 0 Downvote
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