let toggleFullscreen = (elem) => {
    elem = elem || document.documentElement;
    if (!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 (elem.webkitRequestFullscreen) {
            elem.webkitRequestFullscreen(Element.ALLOW_KEYBOARD_INPUT);
        }
    } else {
        if (document.exitFullscreen) {
            document.exitFullscreen();
        } else if (document.msExitFullscreen) {
            document.msExitFullscreen();
        } else if (document.mozCancelFullScreen) {
            document.mozCancelFullScreen();
        } else if (document.webkitExitFullscreen) {
            document.webkitExitFullscreen();
        }
    }
};

let isInFullScreenMode = () => {
    if (document.fullscreenElement || document.webkitFullscreenElement || document.mozFullScreenElement) {
        return true;
    }
    return false;
};

let addFullscreenOnClick = (element) => {
    element.addEventListener('click', () => {
        toggleFullscreen(element);
    });
};