To get HTML5 elements to enter full screen mode, you need to call the requestFullscreen() method and handle browser compatibility. 1. After obtaining the DOM element, call the prefixed requestFullscreen method to achieve full screen; 2. The full screen request must be triggered by user gestures, such as click events; 3. The full screen status can be judged through document.fullscreenElement and listened to full screenchange events; 4. To exit full screen, you can use document.exitFullscreen or the corresponding browser prefix method.

It is actually not complicated to let HTML5 elements enter full screen mode, but there are several key points that need to be paid attention to. Modern browsers support JavaScript's Fullscreen API, through this interface, you can control an element in the page to enter the full screen display state.

Common ways to request full screen

The core of implementing full-screen function is to call requestFullscreen() method. This method belongs to the Element interface, so you must first get a DOM element and then call it.

 const element = document.getElementById('myElement');
element.requestFullscreen();

Different browsers may require prefixed versions, such as webkitRequestFullscreen (Safari) or mozRequestFullScreen (Firefox), so it is recommended to make a compatibility package in actual use:

 function enterFullscreen(element) {
  if (element.requestFullscreen) {
    element.requestFullscreen();
  } else if (element.webkitRequestFullscreen) {
    element.webkitRequestFullscreen();
  } else if (element.mozRequestFullScreen) {
    element.mozRequestFullScreen();
  } else if (element.msRequestFullscreen) {
    element.msRequestFullscreen();
  }
}

The best time to trigger full-screen operation

For security and user experience considerations, browsers usually require full-screen requests to be triggered by user gestures, such as clicks, touches and other events. That is to say, requestFullscreen() cannot be automatically called after the page loads, otherwise an error will be thrown or blocked by the browser.

The correct way is to bind a button click event to trigger:

 <button onclick="enterFullscreen(document.getElementById(&#39;myElement&#39;))">Enter full screen</button>

If you try to execute a full screen request under asynchronous callbacks or non-user behavior, you may encounter a prompt like "fullscreen not allowed".

Determine whether it is currently in full screen

You can use document.fullscreenElement to determine whether there are currently elements in full screen. If null is returned, it means that no element is in full screen; if there is a value, it means that the element currently in full screen.

 if (document.fullscreenElement) {
  console.log('There is currently an element in full screen');
} else {
  console.log('Not currently full screen');
}

In addition, you can also listen for full-screen changes:

 document.addEventListener('fullscreenchange', function () {
  if (document.fullscreenElement) {
    console.log('Enter full screen');
  } else {
    console.log('Exit full screen');
  }
});

Don't forget to add browser prefixes such as webkitfullscreenchange or mozfullscreenchange .

Exit full screen way

In addition to pressing the ESC key to exit, you can also actively exit through the code:

 document.exitFullscreen();

Similarly, browser compatibility needs to be considered:

 if (document.exitFullscreen) {
  document.exitFullscreen();
} else if (document.webkitExitFullscreen) {
  document.webkitExitFullscreen();
} else if (document.mozCancelFullScreen) {
  document.mozCancelFullScreen();
} else if (document.msExitFullscreen) {
  document.msExitFullscreen();
}

Basically that's it. After mastering these key points, you can flexibly control the full-screen behavior of HTML5 elements in the web page.

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