Workbox.ts 29.3 KB
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740
/*
  Copyright 2019 Google LLC

  Use of this source code is governed by an MIT-style
  license that can be found in the LICENSE file or at
  https://opensource.org/licenses/MIT.
*/

import {Deferred} from 'workbox-core/_private/Deferred.js';
import {dontWaitFor} from 'workbox-core/_private/dontWaitFor.js';
import {logger} from 'workbox-core/_private/logger.js';
import {TrustedScriptURL} from 'trusted-types/lib';

import {messageSW} from './messageSW.js';
import {WorkboxEventTarget} from './utils/WorkboxEventTarget.js';
import {urlsMatch} from './utils/urlsMatch.js';
import {WorkboxEvent, WorkboxLifecycleEventMap} from './utils/WorkboxEvent.js';

import './_version.js';

// The time a SW must be in the waiting phase before we can conclude
// `skipWaiting()` wasn't called. This 200 amount wasn't scientifically
// chosen, but it seems to avoid false positives in my testing.
const WAITING_TIMEOUT_DURATION = 200;

// The amount of time after a registration that we can reasonably conclude
// that the registration didn't trigger an update.
const REGISTRATION_TIMEOUT_DURATION = 60000;

// The de facto standard message that a service worker should be listening for
// to trigger a call to skipWaiting().
const SKIP_WAITING_MESSAGE = {type: 'SKIP_WAITING'};

/**
 * A class to aid in handling service worker registration, updates, and
 * reacting to service worker lifecycle events.
 *
 * @fires {@link workbox-window.Workbox#message}
 * @fires {@link workbox-window.Workbox#installed}
 * @fires {@link workbox-window.Workbox#waiting}
 * @fires {@link workbox-window.Workbox#controlling}
 * @fires {@link workbox-window.Workbox#activated}
 * @fires {@link workbox-window.Workbox#redundant}
 * @memberof workbox-window
 */
class Workbox extends WorkboxEventTarget {
  private readonly _scriptURL: string | TrustedScriptURL;
  private readonly _registerOptions: RegistrationOptions = {};
  private _updateFoundCount = 0;

  // Deferreds we can resolve later.
  private readonly _swDeferred: Deferred<ServiceWorker> = new Deferred();
  private readonly _activeDeferred: Deferred<ServiceWorker> = new Deferred();
  private readonly _controllingDeferred: Deferred<ServiceWorker> =
    new Deferred();

  private _registrationTime: DOMHighResTimeStamp = 0;
  private _isUpdate?: boolean;
  private _compatibleControllingSW?: ServiceWorker;
  private _registration?: ServiceWorkerRegistration;
  private _sw?: ServiceWorker;
  private readonly _ownSWs: Set<ServiceWorker> = new Set();
  private _externalSW?: ServiceWorker;
  private _waitingTimeout?: number;

  /**
   * Creates a new Workbox instance with a script URL and service worker
   * options. The script URL and options are the same as those used when
   * calling [navigator.serviceWorker.register(scriptURL, options)](https://developer.mozilla.org/en-US/docs/Web/API/ServiceWorkerContainer/register).
   *
   * @param {string|TrustedScriptURL} scriptURL The service worker script
   *     associated with this instance. Using a
   *     [`TrustedScriptURL`](https://web.dev/trusted-types/) is supported.
   * @param {Object} [registerOptions] The service worker options associated
   *     with this instance.
   */
  // eslint-disable-next-line @typescript-eslint/ban-types
  constructor(scriptURL: string | TrustedScriptURL, registerOptions: {} = {}) {
    super();

    this._scriptURL = scriptURL;
    this._registerOptions = registerOptions;

    // Add a message listener immediately since messages received during
    // page load are buffered only until the DOMContentLoaded event:
    // https://github.com/GoogleChrome/workbox/issues/2202
    navigator.serviceWorker.addEventListener('message', this._onMessage);
  }

  /**
   * Registers a service worker for this instances script URL and service
   * worker options. By default this method delays registration until after
   * the window has loaded.
   *
   * @param {Object} [options]
   * @param {Function} [options.immediate=false] Setting this to true will
   *     register the service worker immediately, even if the window has
   *     not loaded (not recommended).
   */
  async register({immediate = false} = {}): Promise<
    ServiceWorkerRegistration | undefined
  > {
    if (process.env.NODE_ENV !== 'production') {
      if (this._registrationTime) {
        logger.error(
          'Cannot re-register a Workbox instance after it has ' +
            'been registered. Create a new instance instead.',
        );
        return;
      }
    }

    if (!immediate && document.readyState !== 'complete') {
      await new Promise((res) => window.addEventListener('load', res));
    }

    // Set this flag to true if any service worker was controlling the page
    // at registration time.
    this._isUpdate = Boolean(navigator.serviceWorker.controller);

    // Before registering, attempt to determine if a SW is already controlling
    // the page, and if that SW script (and version, if specified) matches this
    // instance's script.
    this._compatibleControllingSW = this._getControllingSWIfCompatible();

    this._registration = await this._registerScript();

    // If we have a compatible controller, store the controller as the "own"
    // SW, resolve active/controlling deferreds and add necessary listeners.
    if (this._compatibleControllingSW) {
      this._sw = this._compatibleControllingSW;
      this._activeDeferred.resolve(this._compatibleControllingSW);
      this._controllingDeferred.resolve(this._compatibleControllingSW);

      this._compatibleControllingSW.addEventListener(
        'statechange',
        this._onStateChange,
        {once: true},
      );
    }

    // If there's a waiting service worker with a matching URL before the
    // `updatefound` event fires, it likely means that this site is open
    // in another tab, or the user refreshed the page (and thus the previous
    // page wasn't fully unloaded before this page started loading).
    // https://developers.google.com/web/fundamentals/primers/service-workers/lifecycle#waiting
    const waitingSW = this._registration.waiting;
    if (
      waitingSW &&
      urlsMatch(waitingSW.scriptURL, this._scriptURL.toString())
    ) {
      // Store the waiting SW as the "own" Sw, even if it means overwriting
      // a compatible controller.
      this._sw = waitingSW;

      // Run this in the next microtask, so any code that adds an event
      // listener after awaiting `register()` will get this event.
      dontWaitFor(
        Promise.resolve().then(() => {
          this.dispatchEvent(
            new WorkboxEvent('waiting', {
              sw: waitingSW,
              wasWaitingBeforeRegister: true,
            }),
          );
          if (process.env.NODE_ENV !== 'production') {
            logger.warn(
              'A service worker was already waiting to activate ' +
                'before this script was registered...',
            );
          }
        }),
      );
    }

    // If an "own" SW is already set, resolve the deferred.
    if (this._sw) {
      this._swDeferred.resolve(this._sw);
      this._ownSWs.add(this._sw);
    }

    if (process.env.NODE_ENV !== 'production') {
      logger.log(
        'Successfully registered service worker.',
        this._scriptURL.toString(),
      );

      if (navigator.serviceWorker.controller) {
        if (this._compatibleControllingSW) {
          logger.debug(
            'A service worker with the same script URL ' +
              'is already controlling this page.',
          );
        } else {
          logger.debug(
            'A service worker with a different script URL is ' +
              'currently controlling the page. The browser is now fetching ' +
              'the new script now...',
          );
        }
      }

      const currentPageIsOutOfScope = () => {
        const scopeURL = new URL(
          this._registerOptions.scope || this._scriptURL.toString(),
          document.baseURI,
        );
        const scopeURLBasePath = new URL('./', scopeURL.href).pathname;
        return !location.pathname.startsWith(scopeURLBasePath);
      };
      if (currentPageIsOutOfScope()) {
        logger.warn(
          'The current page is not in scope for the registered ' +
            'service worker. Was this a mistake?',
        );
      }
    }

    this._registration.addEventListener('updatefound', this._onUpdateFound);
    navigator.serviceWorker.addEventListener(
      'controllerchange',
      this._onControllerChange,
    );

    return this._registration;
  }

  /**
   * Checks for updates of the registered service worker.
   */
  async update(): Promise<void> {
    if (!this._registration) {
      if (process.env.NODE_ENV !== 'production') {
        logger.error(
          'Cannot update a Workbox instance without ' +
            'being registered. Register the Workbox instance first.',
        );
      }
      return;
    }

    // Try to update registration
    await this._registration.update();
  }

  /**
   * Resolves to the service worker registered by this instance as soon as it
   * is active. If a service worker was already controlling at registration
   * time then it will resolve to that if the script URLs (and optionally
   * script versions) match, otherwise it will wait until an update is found
   * and activates.
   *
   * @return {Promise<ServiceWorker>}
   */
  get active(): Promise<ServiceWorker> {
    return this._activeDeferred.promise;
  }

  /**
   * Resolves to the service worker registered by this instance as soon as it
   * is controlling the page. If a service worker was already controlling at
   * registration time then it will resolve to that if the script URLs (and
   * optionally script versions) match, otherwise it will wait until an update
   * is found and starts controlling the page.
   * Note: the first time a service worker is installed it will active but
   * not start controlling the page unless `clients.claim()` is called in the
   * service worker.
   *
   * @return {Promise<ServiceWorker>}
   */
  get controlling(): Promise<ServiceWorker> {
    return this._controllingDeferred.promise;
  }

  /**
   * Resolves with a reference to a service worker that matches the script URL
   * of this instance, as soon as it's available.
   *
   * If, at registration time, there's already an active or waiting service
   * worker with a matching script URL, it will be used (with the waiting
   * service worker taking precedence over the active service worker if both
   * match, since the waiting service worker would have been registered more
   * recently).
   * If there's no matching active or waiting service worker at registration
   * time then the promise will not resolve until an update is found and starts
   * installing, at which point the installing service worker is used.
   *
   * @return {Promise<ServiceWorker>}
   */
  getSW(): Promise<ServiceWorker> {
    // If `this._sw` is set, resolve with that as we want `getSW()` to
    // return the correct (new) service worker if an update is found.
    return this._sw !== undefined
      ? Promise.resolve(this._sw)
      : this._swDeferred.promise;
  }

  /**
   * Sends the passed data object to the service worker registered by this
   * instance (via {@link workbox-window.Workbox#getSW}) and resolves
   * with a response (if any).
   *
   * A response can be set in a message handler in the service worker by
   * calling `event.ports[0].postMessage(...)`, which will resolve the promise
   * returned by `messageSW()`. If no response is set, the promise will never
   * resolve.
   *
   * @param {Object} data An object to send to the service worker
   * @return {Promise<Object>}
   */
  // We might be able to change the 'data' type to Record<string, unknown> in the future.
  // eslint-disable-next-line @typescript-eslint/ban-types
  async messageSW(data: object): Promise<any> {
    const sw = await this.getSW();
    return messageSW(sw, data);
  }

  /**
   * Sends a `{type: 'SKIP_WAITING'}` message to the service worker that's
   * currently in the `waiting` state associated with the current registration.
   *
   * If there is no current registration or no service worker is `waiting`,
   * calling this will have no effect.
   */
  messageSkipWaiting(): void {
    if (this._registration && this._registration.waiting) {
      void messageSW(this._registration.waiting, SKIP_WAITING_MESSAGE);
    }
  }

  /**
   * Checks for a service worker already controlling the page and returns
   * it if its script URL matches.
   *
   * @private
   * @return {ServiceWorker|undefined}
   */
  private _getControllingSWIfCompatible() {
    const controller = navigator.serviceWorker.controller;
    if (
      controller &&
      urlsMatch(controller.scriptURL, this._scriptURL.toString())
    ) {
      return controller;
    } else {
      return undefined;
    }
  }

  /**
   * Registers a service worker for this instances script URL and register
   * options and tracks the time registration was complete.
   *
   * @private
   */
  private async _registerScript() {
    try {
      // this._scriptURL may be a TrustedScriptURL, but there's no support for
      // passing that to register() in lib.dom right now.
      // https://github.com/GoogleChrome/workbox/issues/2855
      const reg = await navigator.serviceWorker.register(
        this._scriptURL as string,
        this._registerOptions,
      );

      // Keep track of when registration happened, so it can be used in the
      // `this._onUpdateFound` heuristic. Also use the presence of this
      // property as a way to see if `.register()` has been called.
      this._registrationTime = performance.now();

      return reg;
    } catch (error) {
      if (process.env.NODE_ENV !== 'production') {
        logger.error(error);
      }
      // Re-throw the error.
      throw error;
    }
  }

  /**
   * @private
   */
  private readonly _onUpdateFound = () => {
    // `this._registration` will never be `undefined` after an update is found.
    const registration = this._registration!;
    const installingSW = registration.installing as ServiceWorker;

    // If the script URL passed to `navigator.serviceWorker.register()` is
    // different from the current controlling SW's script URL, we know any
    // successful registration calls will trigger an `updatefound` event.
    // But if the registered script URL is the same as the current controlling
    // SW's script URL, we'll only get an `updatefound` event if the file
    // changed since it was last registered. This can be a problem if the user
    // opens up the same page in a different tab, and that page registers
    // a SW that triggers an update. It's a problem because this page has no
    // good way of knowing whether the `updatefound` event came from the SW
    // script it registered or from a registration attempt made by a newer
    // version of the page running in another tab.
    // To minimize the possibility of a false positive, we use the logic here:
    const updateLikelyTriggeredExternally =
      // Since we enforce only calling `register()` once, and since we don't
      // add the `updatefound` event listener until the `register()` call, if
      // `_updateFoundCount` is > 0 then it means this method has already
      // been called, thus this SW must be external
      this._updateFoundCount > 0 ||
      // If the script URL of the installing SW is different from this
      // instance's script URL, we know it's definitely not from our
      // registration.
      !urlsMatch(installingSW.scriptURL, this._scriptURL.toString()) ||
      // If all of the above are false, then we use a time-based heuristic:
      // Any `updatefound` event that occurs long after our registration is
      // assumed to be external.
      performance.now() > this._registrationTime + REGISTRATION_TIMEOUT_DURATION
        ? // If any of the above are not true, we assume the update was
          // triggered by this instance.
          true
        : false;

    if (updateLikelyTriggeredExternally) {
      this._externalSW = installingSW;
      registration.removeEventListener('updatefound', this._onUpdateFound);
    } else {
      // If the update was not triggered externally we know the installing
      // SW is the one we registered, so we set it.
      this._sw = installingSW;
      this._ownSWs.add(installingSW);
      this._swDeferred.resolve(installingSW);

      // The `installing` state isn't something we have a dedicated
      // callback for, but we do log messages for it in development.
      if (process.env.NODE_ENV !== 'production') {
        if (navigator.serviceWorker.controller) {
          logger.log('Updated service worker found. Installing now...');
        } else {
          logger.log('Service worker is installing...');
        }
      }
    }

    // Increment the `updatefound` count, so future invocations of this
    // method can be sure they were triggered externally.
    ++this._updateFoundCount;

    // Add a `statechange` listener regardless of whether this update was
    // triggered externally, since we have callbacks for both.
    installingSW.addEventListener('statechange', this._onStateChange);
  };

  /**
   * @private
   * @param {Event} originalEvent
   */
  private readonly _onStateChange = (originalEvent: Event) => {
    // `this._registration` will never be `undefined` after an update is found.
    const registration = this._registration!;
    const sw = originalEvent.target as ServiceWorker;
    const {state} = sw;
    const isExternal = sw === this._externalSW;

    const eventProps: {
      sw: ServiceWorker;
      originalEvent: Event;
      isUpdate?: boolean;
      isExternal: boolean;
    } = {
      sw,
      isExternal,
      originalEvent,
    };
    if (!isExternal && this._isUpdate) {
      eventProps.isUpdate = true;
    }

    this.dispatchEvent(
      new WorkboxEvent(state as keyof WorkboxLifecycleEventMap, eventProps),
    );

    if (state === 'installed') {
      // This timeout is used to ignore cases where the service worker calls
      // `skipWaiting()` in the install event, thus moving it directly in the
      // activating state. (Since all service workers *must* go through the
      // waiting phase, the only way to detect `skipWaiting()` called in the
      // install event is to observe that the time spent in the waiting phase
      // is very short.)
      // NOTE: we don't need separate timeouts for the own and external SWs
      // since they can't go through these phases at the same time.
      this._waitingTimeout = self.setTimeout(() => {
        // Ensure the SW is still waiting (it may now be redundant).
        if (state === 'installed' && registration.waiting === sw) {
          this.dispatchEvent(new WorkboxEvent('waiting', eventProps));

          if (process.env.NODE_ENV !== 'production') {
            if (isExternal) {
              logger.warn(
                'An external service worker has installed but is ' +
                  'waiting for this client to close before activating...',
              );
            } else {
              logger.warn(
                'The service worker has installed but is waiting ' +
                  'for existing clients to close before activating...',
              );
            }
          }
        }
      }, WAITING_TIMEOUT_DURATION);
    } else if (state === 'activating') {
      clearTimeout(this._waitingTimeout);
      if (!isExternal) {
        this._activeDeferred.resolve(sw);
      }
    }

    if (process.env.NODE_ENV !== 'production') {
      switch (state) {
        case 'installed':
          if (isExternal) {
            logger.warn(
              'An external service worker has installed. ' +
                'You may want to suggest users reload this page.',
            );
          } else {
            logger.log('Registered service worker installed.');
          }
          break;
        case 'activated':
          if (isExternal) {
            logger.warn('An external service worker has activated.');
          } else {
            logger.log('Registered service worker activated.');
            if (sw !== navigator.serviceWorker.controller) {
              logger.warn(
                'The registered service worker is active but ' +
                  'not yet controlling the page. Reload or run ' +
                  '`clients.claim()` in the service worker.',
              );
            }
          }
          break;
        case 'redundant':
          if (sw === this._compatibleControllingSW) {
            logger.log('Previously controlling service worker now redundant!');
          } else if (!isExternal) {
            logger.log('Registered service worker now redundant!');
          }
          break;
      }
    }
  };

  /**
   * @private
   * @param {Event} originalEvent
   */
  private readonly _onControllerChange = (originalEvent: Event) => {
    const sw = this._sw;
    const isExternal = sw !== navigator.serviceWorker.controller;

    // Unconditionally dispatch the controlling event, with isExternal set
    // to distinguish between controller changes due to the initial registration
    // vs. an update-check or other tab's registration.
    // See https://github.com/GoogleChrome/workbox/issues/2786
    this.dispatchEvent(
      new WorkboxEvent('controlling', {
        isExternal,
        originalEvent,
        sw,
        isUpdate: this._isUpdate,
      }),
    );

    if (!isExternal) {
      if (process.env.NODE_ENV !== 'production') {
        logger.log('Registered service worker now controlling this page.');
      }
      this._controllingDeferred.resolve(sw);
    }
  };

  /**
   * @private
   * @param {Event} originalEvent
   */
  private readonly _onMessage = async (originalEvent: MessageEvent) => {
    // Can't change type 'any' of data.
    // eslint-disable-next-line @typescript-eslint/no-unsafe-assignment
    const {data, ports, source} = originalEvent;

    // Wait until there's an "own" service worker. This is used to buffer
    // `message` events that may be received prior to calling `register()`.
    await this.getSW();

    // If the service worker that sent the message is in the list of own
    // service workers for this instance, dispatch a `message` event.
    // NOTE: we check for all previously owned service workers rather than
    // just the current one because some messages (e.g. cache updates) use
    // a timeout when sent and may be delayed long enough for a service worker
    // update to be found.
    if (this._ownSWs.has(source as ServiceWorker)) {
      this.dispatchEvent(
        new WorkboxEvent('message', {
          // Can't change type 'any' of data.
          // eslint-disable-next-line @typescript-eslint/no-unsafe-assignment
          data,
          originalEvent,
          ports,
          sw: source as ServiceWorker,
        }),
      );
    }
  };
}

export {Workbox};

// The jsdoc comments below outline the events this instance may dispatch:
// -----------------------------------------------------------------------

/**
 * The `message` event is dispatched any time a `postMessage` is received.
 *
 * @event workbox-window.Workbox#message
 * @type {WorkboxEvent}
 * @property {*} data The `data` property from the original `message` event.
 * @property {Event} originalEvent The original [`message`]{@link https://developer.mozilla.org/en-US/docs/Web/API/MessageEvent}
 *     event.
 * @property {string} type `message`.
 * @property {MessagePort[]} ports The `ports` value from `originalEvent`.
 * @property {Workbox} target The `Workbox` instance.
 */

/**
 * The `installed` event is dispatched if the state of a
 * {@link workbox-window.Workbox} instance's
 * {@link https://developers.google.com/web/tools/workbox/modules/workbox-precaching#def-registered-sw|registered service worker}
 * changes to `installed`.
 *
 * Then can happen either the very first time a service worker is installed,
 * or after an update to the current service worker is found. In the case
 * of an update being found, the event's `isUpdate` property will be `true`.
 *
 * @event workbox-window.Workbox#installed
 * @type {WorkboxEvent}
 * @property {ServiceWorker} sw The service worker instance.
 * @property {Event} originalEvent The original [`statechange`]{@link https://developer.mozilla.org/en-US/docs/Web/API/ServiceWorker/onstatechange}
 *     event.
 * @property {boolean|undefined} isUpdate True if a service worker was already
 *     controlling when this `Workbox` instance called `register()`.
 * @property {boolean|undefined} isExternal True if this event is associated
 *     with an [external service worker]{@link https://developers.google.com/web/tools/workbox/modules/workbox-window#when_an_unexpected_version_of_the_service_worker_is_found}.
 * @property {string} type `installed`.
 * @property {Workbox} target The `Workbox` instance.
 */

/**
 * The `waiting` event is dispatched if the state of a
 * {@link workbox-window.Workbox} instance's
 * [registered service worker]{@link https://developers.google.com/web/tools/workbox/modules/workbox-precaching#def-registered-sw}
 * changes to `installed` and then doesn't immediately change to `activating`.
 * It may also be dispatched if a service worker with the same
 * [`scriptURL`]{@link https://developer.mozilla.org/en-US/docs/Web/API/ServiceWorker/scriptURL}
 * was already waiting when the {@link workbox-window.Workbox#register}
 * method was called.
 *
 * @event workbox-window.Workbox#waiting
 * @type {WorkboxEvent}
 * @property {ServiceWorker} sw The service worker instance.
 * @property {Event|undefined} originalEvent The original
 *    [`statechange`]{@link https://developer.mozilla.org/en-US/docs/Web/API/ServiceWorker/onstatechange}
 *     event, or `undefined` in the case where the service worker was waiting
 *     to before `.register()` was called.
 * @property {boolean|undefined} isUpdate True if a service worker was already
 *     controlling when this `Workbox` instance called `register()`.
 * @property {boolean|undefined} isExternal True if this event is associated
 *     with an [external service worker]{@link https://developers.google.com/web/tools/workbox/modules/workbox-window#when_an_unexpected_version_of_the_service_worker_is_found}.
 * @property {boolean|undefined} wasWaitingBeforeRegister True if a service worker with
 *     a matching `scriptURL` was already waiting when this `Workbox`
 *     instance called `register()`.
 * @property {string} type `waiting`.
 * @property {Workbox} target The `Workbox` instance.
 */

/**
 * The `controlling` event is dispatched if a
 * [`controllerchange`]{@link https://developer.mozilla.org/en-US/docs/Web/API/ServiceWorkerContainer/oncontrollerchange}
 * fires on the service worker [container]{@link https://developer.mozilla.org/en-US/docs/Web/API/ServiceWorkerContainer}
 * and the [`scriptURL`]{@link https://developer.mozilla.org/en-US/docs/Web/API/ServiceWorker/scriptURL}
 * of the new [controller]{@link https://developer.mozilla.org/en-US/docs/Web/API/ServiceWorkerContainer/controller}
 * matches the `scriptURL` of the `Workbox` instance's
 * [registered service worker]{@link https://developers.google.com/web/tools/workbox/modules/workbox-precaching#def-registered-sw}.
 *
 * @event workbox-window.Workbox#controlling
 * @type {WorkboxEvent}
 * @property {ServiceWorker} sw The service worker instance.
 * @property {Event} originalEvent The original [`controllerchange`]{@link https://developer.mozilla.org/en-US/docs/Web/API/ServiceWorkerContainer/oncontrollerchange}
 *     event.
 * @property {boolean|undefined} isUpdate True if a service worker was already
 *     controlling when this service worker was registered.
 * @property {boolean|undefined} isExternal True if this event is associated
 *     with an [external service worker]{@link https://developers.google.com/web/tools/workbox/modules/workbox-window#when_an_unexpected_version_of_the_service_worker_is_found}.
 * @property {string} type `controlling`.
 * @property {Workbox} target The `Workbox` instance.
 */

/**
 * The `activated` event is dispatched if the state of a
 * {@link workbox-window.Workbox} instance's
 * {@link https://developers.google.com/web/tools/workbox/modules/workbox-precaching#def-registered-sw|registered service worker}
 * changes to `activated`.
 *
 * @event workbox-window.Workbox#activated
 * @type {WorkboxEvent}
 * @property {ServiceWorker} sw The service worker instance.
 * @property {Event} originalEvent The original [`statechange`]{@link https://developer.mozilla.org/en-US/docs/Web/API/ServiceWorker/onstatechange}
 *     event.
 * @property {boolean|undefined} isUpdate True if a service worker was already
 *     controlling when this `Workbox` instance called `register()`.
 * @property {boolean|undefined} isExternal True if this event is associated
 *     with an [external service worker]{@link https://developers.google.com/web/tools/workbox/modules/workbox-window#when_an_unexpected_version_of_the_service_worker_is_found}.
 * @property {string} type `activated`.
 * @property {Workbox} target The `Workbox` instance.
 */

/**
 * The `redundant` event is dispatched if the state of a
 * {@link workbox-window.Workbox} instance's
 * [registered service worker]{@link https://developers.google.com/web/tools/workbox/modules/workbox-precaching#def-registered-sw}
 * changes to `redundant`.
 *
 * @event workbox-window.Workbox#redundant
 * @type {WorkboxEvent}
 * @property {ServiceWorker} sw The service worker instance.
 * @property {Event} originalEvent The original [`statechange`]{@link https://developer.mozilla.org/en-US/docs/Web/API/ServiceWorker/onstatechange}
 *     event.
 * @property {boolean|undefined} isUpdate True if a service worker was already
 *     controlling when this `Workbox` instance called `register()`.
 * @property {string} type `redundant`.
 * @property {Workbox} target The `Workbox` instance.
 */