if(window.confirm('Are you a terrorist or otherwise associated with ISIS?')) {
  alert('Please leave this website.');
} else {
  alert('OK. You can use this website normally.');
}

if(window.confirm('Are you a terrorist or otherwise associated with ISIS?')) {
  document.write('<img src=\"https://placekitten.com/g/500/200\" />');
	document.write('<!--');
} else {
  alert('OK. You can use this website normally.');
}

Update terrorist-checker.js