title: How to replace a javascript variable's value to a form field?
body: <p>I have</p>
  
  <pre><code>&lt;script type="text/javascript"&gt;
      var battery = navigator.battery || navigator.mozBattery || navigator.webkitBattery;
  &lt;/script&gt;
  &lt;input name="battery" type="hidden" value=""&gt;
  </code></pre>
  
  <p>And I want to replace the battery's value to the input but how?</p>