进入全屏

function full(ele) {
      if (ele.requestFullscreen) {
          ele.requestFullscreen();
      } else if (ele.mozRequestFullScreen) {
          ele.mozRequestFullScreen();
      } else if (ele.webkitRequestFullscreen) {
          ele.webkitRequestFullscreen();
      } else if (ele.msRequestFullscreen) {
          ele.msRequestFullscreen();
      }
}

退出全屏

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

获取当前全屏的节点

function getFullscreenElement() {
    return (        
        document.fullscreenElement ||
        document.mozFullScreenElement ||
        document.msFullScreenElement ||
        document.webkitFullscreenElement||null
    );
}

判断当前是否全屏

function isFullScreen() {
  return  !! (
      document.fullscreen || 
      document.mozFullScreen ||                         
      document.webkitIsFullScreen ||       
      document.webkitFullScreen || 
      document.msFullScreen 
   );
}

判断当前文档是否能切换到全屏

function isFullscreenEnabled() {
    return  (
        document.fullscreenEnabled ||
        document.mozFullScreenEnabled ||
        document.webkitFullscreenEnabled ||
        document.msFullscreenEnabled
    );
}

全屏事件

document.addEventListener('fullscreenchange', evt => {
    if (document.fullscreenElement) {
        console.log('进入全屏')
    } else {
        console.log('退出全屏')
    }
})

注:
1.document下没有requestFullscreen
2.requestFullscreen方法只能由用户触发，比如：在onload事件中不能触发
3.页面跳转需先退出全屏
4.进入全屏的元素，将脱离其父元素，所以可能导致之前某些css的失效
解决方案：使用 :full-screen伪类 为元素添加全屏时的样式（使用时为了兼容注意添加-webkit、-moz或-ms前缀）
5.一个元素A全屏后，其子元素要再全屏，需先让元素A退出全屏