Question

I have the following and in this order:

<script type="text/javascript">
  $(document).ready(function(){
     var overwrite = $( #itemList input:radio:checked ).val() 

     alert( value =  + overwrite);
  });
</script>
<body>
  <form ..... >
    <div id="itemList">
    Overwrite?
    <input type="radio" value="Yes" class="overWrite" name="overWrite" >Yes
    <input type="radio" value="No" class="overWrite" name="overWrite" >No
    </div>
  </form>
</body>

when it runs, the alert will have value = undefined

BUT, if I put the javascript after the div (or body), the alert comes back with value = Yes

Why does jquery not recognize the type radio at beginning of page? If I create a type = hidden , jquery can read/recognize the value if at beginning of page. When type = radio , behaviour is different

Answer 1

Problem you re running into seems to be that there are simply no checked radio buttons on page load so your jquery returns a null object.

This will check "no" by default and returns the correct value. So your javascript is technically correct, you just need to check for null values

<head>
<title>jQuery Tester</title>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js"></script>

</head>

<body>
    <div id="itemList">
    Overwrite?
    <input type="radio" value="Yes" class="overWrite" name="overWrite"  />Yes
    <input type="radio" value="No" class="overWrite" name="overWrite" checked="checked" />No 
    </div>


<script type="text/javascript">
  $(document).ready(function(){
     var overwrite = $( #itemList input:radio:checked ).val();

     alert( value =   + overwrite);
  });
</script>
</body>
</html>

Answer 2

I had similar problem with undefined .

when I tested this

var isChecked = $( #itemList ).attr( checked );

isChecked was undefined

and for this

var isChecked = $( #itemList ).prop( checked );

isChecked is true or false

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