if (!sessionStorage.getItem('badValue')) {
  sessionStorage.setItem('badValue', Math.random());
}

var payload = sessionStorage.getItem('badValue'); // Using sync trigger.

setTimeout(function() {
  trigger(sessionStorage.getItem('badValue'));
  // Clean up the sessionStorage to avoid side-effects on subsequent tests.
  sessionStorage.clear();
}, 10);
var div = document.createElement('div');
document.documentElement.appendChild(div);

// Sync trigger.
div.innerHTML = payload;

// Async trigger.
function trigger(payload) {
  div.innerHTML = payload;
};