如何让应用程序通过按钮实现全屏显示

<button id="fullscreen-btn">全屏显示</button>

var fullscreenBtn = document.getElementById('fullscreen-btn');

// 检测浏览器是否支持全屏API
var fullscreenEnabled = document.fullscreenEnabled || document.mozFullScreenEnabled || document.webkitFullscreenEnabled;

// 全屏显示函数
function enterFullscreen() {
  var element = document.documentElement; // 获取整个页面的元素

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

// 退出全屏函数
function exitFullscreen() {
  if (document.exitFullscreen) {
    document.exitFullscreen();
  } else if (document.mozCancelFullScreen) {
    document.mozCancelFullScreen();
  } else if (document.webkitExitFullscreen) {
    document.webkitExitFullscreen();
  }
}

// 按钮点击事件处理程序
fullscreenBtn.addEventListener('click', function() {
  if (fullscreenEnabled) {
    if (document.fullscreenElement || document.mozFullScreenElement || document.webkitFullscreenElement) {
      exitFullscreen();
    } else {
      enterFullscreen();
    }
  } else {
    // 浏览器不支持全屏API，给出提示或备选方案
    alert('您的浏览器不支持全屏显示功能。');
  }
});