JavaScript NaN error in Internet Explorer

Question

I have a form with radio buttons:

<ul class='likert'>
  <li>
    <input type="radio" name="q1" value=5 required>
  </li>
  <li>
    <input type="radio" name="q1" value=4>
  </li>
  <li>
    <input type="radio" name="q1" value=3 checked="checked">
  </li>
  <li>
    <input type="radio" name="q1" value=2>
  </li>
  <li>
    <input type="radio" name="q1" value=1>
  </li>
</ul>

In Firefox and Chrome,

parseInt(document.forms["question_form"]["q1"].value)

returns 3 (or whatever) but in Internet Explorer I get ‘NaN’.

Answer 1

IE returns a HTMLCollection when the names are not unique in document.forms["question_form"]["q1"].

See Remarks at IHTMLElementCollection

"If duplicate names are found, a collection of those named items is returned."

You can get the checked value for example like this:

var val = document.querySelector('.likert input:checked').value);