| <!doctype html> | |
| <script> | |
| window.onmessage = (e) => { | |
| if (e.data === 'What is document.fullscreenEnabled?') { | |
| e.source.postMessage(document.fullscreenEnabled, '*'); | |
| } else { | |
| e.source.postMessage('Incorrect message', '*'); | |
| } | |
| } | |
| </script> | |
| <p>This page echos document.fullscreenEnabled.</p> |