echo-fullscreenEnabled.html (300B)
1 <!doctype html> 2 <script> 3 window.onmessage = (e) => { 4 if (e.data === 'What is document.fullscreenEnabled?') { 5 e.source.postMessage(document.fullscreenEnabled, '*'); 6 } else { 7 e.source.postMessage('Incorrect message', '*'); 8 } 9 } 10 </script> 11 <p>This page echos document.fullscreenEnabled.</p>