offline-plugin/lib/misc/async-waituntil.js

"use strict";

(function () {
  var waitUntil = ExtendableEvent.prototype.waitUntil;
  var respondWith = FetchEvent.prototype.respondWith;
  var promisesMap = new WeakMap();

  ExtendableEvent.prototype.waitUntil = function (promise) {
    var extendableEvent = this;
    var promises = promisesMap.get(extendableEvent);

    if (promises) {
      promises.push(Promise.resolve(promise));
      return;
    }

    promises = [Promise.resolve(promise)];
    promisesMap.set(extendableEvent, promises);

    // call original method
    return waitUntil.call(extendableEvent, Promise.resolve().then(function processPromises() {
      var len = promises.length;

      // wait for all to settle
      return Promise.all(promises.map(function (p) {
        return p["catch"](function () {});
      })).then(function () {
        // have new items been added? If so, wait again
        if (promises.length != len) return processPromises();
        // we're done!
        promisesMap["delete"](extendableEvent);
        // reject if one of the promises rejected
        return Promise.all(promises);
      });
    }));
  };

  FetchEvent.prototype.respondWith = function (promise) {
    this.waitUntil(promise);
    return respondWith.call(this, promise);
  };
})();