gecko-dev/dom/promise/tests/file_promise_and_timeout_ordering.js

var log = [];
var resolvedPromise = Promise.resolve(null);
function schedulePromiseTask(f) {
  resolvedPromise.then(f);
}

setTimeout(function() {
  log.push("t1start");
  schedulePromiseTask(function() {
    log.push("promise");
  });
  log.push("t1end");
}, 10);

setTimeout(function() {
  log.push("t2");
  postMessage(log.join(", "));
}, 10);