js全屏，模拟F11

function launchFullscreen(element) {
  if (element.requestFullscreencreen) {
    element.requestFullScreen();
  } else if (element.mozRequestFullScreen) {
    element.mozRequestFullScreen();
  } else if (element.webkitRequestFullScreen) {
    element.webkitRequestFullScreen();
  } else if (element.msRequestFullScreen) {
    element.msRequestFullScreen();
  }
}

必须有事件触发，如鼠标事件、键盘事件

$(".head").on("click", function () {
  launchFullscreen(document.documentElement);
});