JS Fullscreen

<!-- TOGGLE FULLSCREEN -->
<a href="https://stackoverflow.com/questions/7179535/set-window-to-fullscreen-real-fullscreen-f11-functionality-by-javascript">Soucre</a>

<input type="button" id="fullscreen" value="Fullscreen" onclick="toggleFullScreen(document.documentElement)">

<script>
function toggleFullScreen(elem) {
    // ## The below if statement seems to work better ## if ((document.fullScreenElement && document.fullScreenElement !== null) || (document.msfullscreenElement && document.msfullscreenElement !== null) || (!document.mozFullScreen && !document.webkitIsFullScreen)) {
    if ((document.fullScreenElement !== undefined && document.fullScreenElement === null) || (document.msFullscreenElement !== undefined && document.msFullscreenElement === null) || (document.mozFullScreen !== undefined && !document.mozFullScreen) || (document.webkitIsFullScreen !== undefined && !document.webkitIsFullScreen)) {
        if (elem.requestFullScreen) {
            elem.requestFullScreen();
        } else if (elem.mozRequestFullScreen) {
            elem.mozRequestFullScreen();
        } else if (elem.webkitRequestFullScreen) {
            elem.webkitRequestFullScreen(Element.ALLOW_KEYBOARD_INPUT);
        } else if (elem.msRequestFullscreen) {
            elem.msRequestFullscreen();
        }
    } else {
        if (document.cancelFullScreen) {
            document.cancelFullScreen();
        } else if (document.mozCancelFullScreen) {
            document.mozCancelFullScreen();
        } else if (document.webkitCancelFullScreen) {
            document.webkitCancelFullScreen();
        } else if (document.msExitFullscreen) {
            document.msExitFullscreen();
        }
    }
}
</script>