title: Check if group of Radio-Buttons has at least one selected
body: <p>I got a problem with my Feedback Form. I'd like to validate with either JQuery or Javascript, that every group of radio-buttons has always one button selected before you the user can submit the form.</p>
  <p>Here's my code from my form.html.</p>
  <pre><code>&lt;form id='form' method='POST' action='validate.php'&gt;
      &lt;table&gt;
          &lt;!-- Table header --&gt;
          &lt;tr&gt;
              &lt;th&gt;&amp;nbsp;&lt;/th&gt;
              &lt;th&gt;Always&lt;/th&gt;
              &lt;th&gt;Often&lt;/th&gt;
              &lt;th&gt;Rarely&lt;/th&gt;
              &lt;th&gt;Never&lt;/th&gt;
          &lt;/tr&gt;
          &lt;!-- Group One --&gt;
          &lt;tr&gt;
              &lt;th&gt;Dummy Text 1&lt;/th&gt;
              &lt;th&gt;&lt;input class='radio' type='radio' name='item[0]' value='always'&gt;&lt;/th&gt;
              &lt;th&gt;&lt;input class='radio' type='radio' name='item[0]' value='often'&gt;&lt;/th&gt;
              &lt;th&gt;&lt;input class='radio' type='radio' name='item[0]' value='rarely'&gt;&lt;/th&gt;
              &lt;th&gt;&lt;input class='radio' type='radio' name='item[0]' value='never'&gt;&lt;/th&gt;
          &lt;/tr&gt;
          &lt;!-- Group two --&gt;
          &lt;tr&gt;
              &lt;th&gt;Dummy Text 2&lt;/th&gt;
              &lt;th&gt;&lt;input class='radio' type='radio' name='item[1]' value='always'&gt;&lt;/th&gt;
              &lt;th&gt;&lt;input class='radio' type='radio' name='item[1]' value='often'&gt;&lt;/th&gt;
              &lt;th&gt;&lt;input class='radio' type='radio' name='item[1]' value='rarely'&gt;&lt;/th&gt;
              &lt;th&gt;&lt;input class='radio' type='radio' name='item[1]' value='never'&gt;&lt;/th&gt;
          &lt;/tr&gt;
          &lt;!-- End of table --&gt;
      &lt;/table&gt;
  &lt;/form&gt;
  &lt;button class='buttons' onclick='subForm()' name='submit'&gt;Send Feedback&lt;/button&gt;
  &lt;script&gt;
      function subForm() {
          //Code
      }
  &lt;/script&gt;
  </code></pre>
  <p>But I dont know what I should use for checking if the radio-buttons are checked.</p>
  <p>I tried to use <code>document.getElementsByName</code> but this gave me back <code>undefined</code> values</p>