document.getElementById("fullscreenButton").onclick = function() {
var iframe = document.querySelector("iframe");
if (iframe.requestFullscreen) {
iframe.requestFullscreen();
} else if (iframe.mozRequestFullScreen) { /* Firefox */
iframe.mozRequestFullScreen();
} else if (iframe.webkitRequestFullscreen) { /* Chrome, Safari & Opera */
iframe.webkitRequestFullscreen();
} else if (iframe.msRequestFullscreen) { /* IE/Edge */
iframe.msRequestFullscreen();
} else {
// Fallback: make the entire document go full screen
document.documentElement.requestFullscreen();
}
};