if (!localStorage.badValue) {
  localStorage.badValue = Math.random();
}
var payload = localStorage.badValue;

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

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

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