javascript script to go fullscreen browser

NOTE: RequestFullScreen needs to be bind to a user action (for security reasons)
//OLDER iron/chrome : document.documentElement.webkitRequestFullScreen()
var elem = document.documentElement;
if (elem.webkitRequestFullScreen) {
  elem.webkitRequestFullScreen();
} else if (elem.mozRequestFullScreen) {
  elem.mozRequestFullScreen();
} else if (elem.requestFullScreen) {
  elem.requestFullScreen();
}

//Newer chrome : document.documentElement.requestFullscreen();

<script>
/* Get the documentElement (<html>) to display the page in fullscreen */
var elem = document.documentElement;

/* View in fullscreen */
function openFullscreen() {
  if (elem.requestFullscreen) {
    elem.requestFullscreen();
  } else if (elem.webkitRequestFullscreen) { /* Safari */
    elem.webkitRequestFullscreen();
  } else if (elem.msRequestFullscreen) { /* IE11 */
    elem.msRequestFullscreen();
  }
}

/* Close fullscreen */
function closeFullscreen() {
  if (document.exitFullscreen) {
    document.exitFullscreen();
  } else if (document.webkitExitFullscreen) { /* Safari */
    document.webkitExitFullscreen();
  } else if (document.msExitFullscreen) { /* IE11 */
    document.msExitFullscreen();
  }
}
</script>