1、全屏

//全屏
var docElm = document.documentElement;
//W3C
if (docElm.requestFullscreen) {
  docElm.requestFullscreen();
}
//FireFox
else if (docElm.mozRequestFullScreen) {
  docElm.mozRequestFullScreen();
}
//Chrome等
else if (docElm.webkitRequestFullScreen) {
  docElm.webkitRequestFullScreen();
}
//IE11
else if (elem.msRequestFullscreen) {
  elem.msRequestFullscreen();
}

2、退出全屏

//W3C
if (document.exitFullscreen) {
  document.exitFullscreen();
}
//FireFox
else if (document.mozCancelFullScreen) {
  document.mozCancelFullScreen();
}
//Chrome等
else if (document.webkitCancelFullScreen) {
  document.webkitCancelFullScreen();
}
//IE11
else if (document.msExitFullscreen) {
  document.msExitFullscreen();
}