title: Update A Hidden FIeld Using Prototype
body: <p>I'm trying to update the value of a hidden form field using Prototype. The form field:</p>
  
  <pre><code>&lt;input id="item_id" name="item_id" value="" type="hidden" /&gt;
  </code></pre>
  
  <p>I'm trying to update the value like so using prototype:</p>
  
  <pre><code>var additionalVal = ',2';
  var itemId = $$('name=["itemid"]');
  itemId.value = (itemId.value + ',' + additionalVal);
  </code></pre>
  
  <p>The element appears to be updated and if I query it using the web inspector, the value has been updated. However, if I look at the hidden field, it still looks like this:</p>
  
  <pre><code>&lt;input id="item_id" name="item_id" value="" type="hidden" /&gt;
  </code></pre>
  
  <p>... an empty value field. Also, submitting it like this enters a null column into the table. Without including my whole JS file (450 lines), can anyone give me a pointer to solve this?</p>
  
  <p>Thank you!</p>