title: Adding element to dom doesn't work
body: <p>When I try to add elements to my dom, they're not added, but when I console.log them, I do get a value <code>&lt;th class="text-right" rowspan="1" colspan="1"&gt;&lt;/th&gt;</code></p>
  
  <pre><code>for(c=0; c&lt;2; c++) {
  
  console.log(document.getElementById('achats_table').tFoot.children[0].appendChild(document.createElement('th')));
      document.getElementById('achats_table').tFoot.children[0].appendChild(document.createElement('th'));
          }
  </code></pre>
  
  <p>Table HTML : </p>
  
  <pre><code>&lt;table&gt;
    &lt;thead&gt;
      &lt;tr&gt;
      &lt;/tr&gt;
    &lt;/thead&gt;
    &lt;tbody&gt;
    &lt;/tbody&gt;
    &lt;tfoot&gt;
      &lt;tr&gt;
      &lt;/tr&gt;
    &lt;/tfoot&gt;
  &lt;/table&gt;
  </code></pre>
  
  <p>what am I doing wrong? how can I debug this? I get no console errors.</p>