--全屏

MDN语法：var Promise = Element.requestFullscreen(options);

兼容写法：

function toFullVideo(){

  if(videoDom.requestFullscreen){

    return videoDom.requestFullscreen();

  }else if(videoDom.webkitRequestFullScreen){

    return videoDom.webkitRequestFullScreen();

  }else if(videoDom.mozRequestFullScreen){

    return videoDom.mozRequestFullScreen();

  }else{

    return videoDom.msRequestFullscreen();

  }

}

--退出全屏

MDN语法：var Promise = Element.exitFullscreen(options);

兼容写法

exitFullscreen() {

    if (document.exitFullscreen) {

      document.exitFullscreen();

    } else if (document.mozCancelFullScreen) {

      document.mozCancelFullScreen();

    } else if (document.webkitExitFullscreen) {

      document.webkitExitFullscreen();

    }

  }