Enter
Exit
Check

This is a demo for three APIs: requestFullScreen, exitFullScreen and fullScreenEnabled.

HTML:

  <a href="javascript:document.documentElement.requestFullScreen()" style="color:red;font-size:50pt">
    Enter
  </a><br>
  <a href="javascript:document.exitFullScreen()" style="color:red;font-size:50pt">
    Exit
  </a><br>
  <a href="javascript:alert(document.fullScreenEnabled)" style="color:red;font-size:50pt">
    Check
  </a><br>