如何在触发上传文件时保持全屏？

var element = document.documentElement;
if (element.requestFullscreen) {
  element.requestFullscreen();
} else if (element.mozRequestFullScreen) {
  element.mozRequestFullScreen();
} else if (element.webkitRequestFullscreen) {
  element.webkitRequestFullscreen();
} else if (element.msRequestFullscreen) {
  element.msRequestFullscreen();
}

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