title: Web browser is not able to capture Windows key + D, why?
body: <p>Web browsers fail to capture windows key shortcut. For instance, Windows key + D displays the desktop. </p>
  
  <p>However, in the browser, JS could only detect the keydown event of the Windows key, but is not able to capture the keyboard event of D or the keyup event of the windows key.</p>
  
  <p>What's the deep reason behind it? Is there any document explaining it?</p>