!document.fullscreenElement && !document.mozFullScreenElement &&
                        !document.webkitFullscreenElement && !document.msFullscreenElement) {
                    if (elem.requestFullscreen) {
                        elem.requestFullscreen();
                    } else if (elem.msRequestFullscreen) {
                        elem.msRequestFullscreen();
                    } else if (elem.mozRequestFullScreen) {
                        elem.mozRequestFullScreen();
                    } else if