devdocs/assets/javascripts/app/update_checker.js

/*
 * decaffeinate suggestions:
 * DS207: Consider shorter variations of null checks
 * Full docs: https://github.com/decaffeinate/decaffeinate/blob/main/docs/suggestions.md
 */
app.UpdateChecker = class UpdateChecker {
  constructor() {
    this.checkDocs = this.checkDocs.bind(this);
    this.onFocus = this.onFocus.bind(this);
    this.lastCheck = Date.now();

    $.on(window, 'focus', this.onFocus);
    if (app.serviceWorker != null) {
      app.serviceWorker.on('updateready', this.onUpdateReady);
    }

    setTimeout(this.checkDocs, 0);
  }

  check() {
    if (app.serviceWorker) {
      app.serviceWorker.update();
    } else {
      ajax({
        url: $('script[src*="application"]').getAttribute('src'),
        dataType: 'application/javascript',
        error: (_, xhr) => { if (xhr.status === 404) { return this.onUpdateReady(); } }
      });
    }
  }

  onUpdateReady() {
    new app.views.Notif('UpdateReady', {autoHide: null});
  }

  checkDocs() {
    if (!app.settings.get('manualUpdate')) {
      app.docs.updateInBackground();
    } else {
      app.docs.checkForUpdates(i => { if (i > 0) { return this.onDocsUpdateReady(); } });
    }
  }

  onDocsUpdateReady() {
    new app.views.Notif('UpdateDocs', {autoHide: null});
  }

  onFocus() {
    if ((Date.now() - this.lastCheck) > 21600e3) {
      this.lastCheck = Date.now();
      this.check();
    }
  }
};