executor.js - mozsearch

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const params = new URLSearchParams(window.location.search);

const uuid = params.get('uuid');

// Executor and BFCache detection

// When navigating out from this page, always call

// `prepareNavigation(callback)` synchronously from the script injected by

// `RemoteContext.execute_script()`, and trigger navigation on or after the

// callback is called.

// prepareNavigation() suspends task polling and avoid in-flight fetch

// requests during navigation that might evict the page from BFCache.

//

// When we navigate to the page again, task polling is resumed, either

// - (BFCache cases) when the pageshow event listener added by

//   prepareNavigation() is executed, or

// - (Non-BFCache cases) when `Executor.execute()` is called again during

//   non-BFCache page loading.

//

// In such scenarios, `assert_bfcached()` etc. in `helper.sub.js` can determine

// whether the page is restored from BFCache or not, by observing

// - `isPageshowFired`: whether the pageshow event listener added by the

//   prepareNavigation() before navigating out, and

// - `loadCount`: whether this inline script is evaluated again.

// - `isPageshowPersisted` is used to assert that `event.persisted` is true

//   when restored from BFCache.

window.isPageshowFired = false;

window.isPageshowPersisted = null;

window.loadCount = parseInt(localStorage.getItem(uuid + '.loadCount') || '0') + 1;

localStorage.setItem(uuid + '.loadCount', loadCount);

window.pageShowPromise = new Promise(resolve =>

  window.addEventListener('pageshow', resolve, {once: true}));

const executor = new Executor(uuid);

window.prepareNavigation = function(callback) {

  window.addEventListener(

    'pageshow',

    (event) => {

      window.isPageshowFired = true;

      window.isPageshowPersisted = event.persisted;

      executor.resume();

},

    {once: true});

  executor.suspend(callback);