title: Converting all text in specific element to uppercase?
body: <p>I am trying to convert all table header text to uppercase but not successful.</p>
  
  <pre><code>&lt;table&gt;
  &lt;tr&gt;
  &lt;th&gt;product name&lt;/th&gt;
  &lt;th&gt;product id&lt;/th&gt;
  ....
  </code></pre>
  
  <p>My script is as follow:</p>
  
  <pre><code>&lt;script&gt;
  var x = document.getElementByTagName('th').innerHTML;
  document.write(x.toUpperCase());
  &lt;/script&gt;
  </code></pre>
  
  <p>Please help....I am learning JS and almost frustrated by this simple thing.</p>