title: HTML textarea value is coming up as 'undefined'
body: <p>I have HTML textareas that 'sometimes' have 'undefined' in the value property - I can't work out what is causing it.</p>
  
  <p>Background: I have a PHP script that generates lots of textareas on a page - each with a unique ID using a counting system.  The textareas belong to different forms that appear on the page. It is like an email inbox with a 'quick reply' form under each email.</p>
  
  <p>Sometimes, when the forms are submitted the corresponding textarea value comes up as 'undefined' instead of the actual value the user has typed into the field.  Example code:</p>
  
  <pre><code>//Javascript
  function quickReply(id)
  {
    message = document.getElementById('textarea_' + id).value();
  
    //Send 'message' and other details to PHP for handling...
  }
  </code></pre>
  
  <p>I have also tried calling the value with the jQuery equivalent:   </p>
  
  <pre><code>$('textarea_' + id).val();
  </code></pre>
  
  <p>Most of the time everything works as expected, but sometimes the value comes up as 'undefined'. 'undefined' is then send to my PHP code in Javascript and ends up getting saved in the database as the 'reply' which is how the issue is being discovered.</p>
  
  <p>What causes a textarea to have an 'undefined' value property?  Anything I can try to resolve this?</p>