Toggle fullscreen html element

function toggleFullScreen(elem) {
  if (document.fullScreenElement || document.mozFullScreenElement || document.webkitIsFullScreen) {
    if (document.cancelFullScreen) document.cancelFullScreen();
    else if (document.mozCancelFullScreen) document.mozCancelFullScreen();
    else if (document.webkitCancelFullScreen) document.webkitCancelFullScreen();
  } else {
    if (elem.requestFullScreen) elem.requestFullScreen();
    else if (elem.mozRequestFullScreen) elem.mozRequestFullScreen();
    else if (elem.webkitRequestFullScreen) elem.webkitRequestFullScreen(Element.ALLOW_KEYBOARD_INPUT);
  }
}