if (!sessionStorage.badValue) {
  sessionStorage.badValue = Math.random();
}

var payload = sessionStorage.badValue;

setTimeout(function() {
  trigger(sessionStorage.badValue); // Using the async trigger.

  // Clean up the sessionStorage to avoid side-effects on subsequent tests.
  sessionStorage.clear();
}, 10)
// Sync trigger.
document.write(payload);

// Async trigger.
function trigger(payload) {
  document.write(payload);
}