JavaScript bridge API

Background jobs

Work that keeps going after the app is closed: a durable auto-save, a periodic sync.

`workCancel` bridge#

window.WebToApk.workCancel(id: String)

No permission needed; results echo as `appmint:work` / window.onAppMintWork.

Described by its group, Background jobs (WorkManager): durable auto-save + periodic native sync, rather than on its own.

Example

Cancels a background job (one-off or repeating) by its id and deletes its saved request.

Returns: nothing directly. The appmint:work event (and window.onAppMintWork) answers { id, status: 'cancelled' }. Needs: nothing.

function stopSync() {
  if (!(window.WebToApk && window.WebToApk.workCancel)) return;
  WebToApk.workCancel('sync');
}

window.addEventListener('appmint:work', function (e) {
  if (e.detail.id === 'sync' && e.detail.status === 'cancelled') {
    document.getElementById('sync-status').textContent = 'Background sync is off';
  }
});

Throw away a draft: cancel its auto-save that has not been sent yet, then clear the editor once Android confirms:

function discardDraft() {
  if (!(window.WebToApk && window.WebToApk.workCancel)) { clearEditor(); return; }
  function onWork(e) {
    if (e.detail.id !== 'autosave' || e.detail.status !== 'cancelled') return;
    window.removeEventListener('appmint:work', onWork);
    clearEditor();
  }
  window.addEventListener('appmint:work', onWork);
  WebToApk.workCancel('autosave');
}

On sign-out, cancel every job this app has, using the ids that workList reports:

function cancelAllJobs() {
  if (!(window.WebToApk && window.WebToApk.workList && window.WebToApk.workCancel)) return;
  const requestId = 'signout-' + Date.now();
  function onWork(e) {
    if (String(e.detail.requestId) !== requestId) return;
    window.removeEventListener('appmint:work', onWork);
    (e.detail.jobs || []).forEach(function (job) {
      WebToApk.workCancel(job.id);                      // each answers { id, status: 'cancelled' }
    });
  }
  window.addEventListener('appmint:work', onWork);
  WebToApk.workList(requestId);
}

Notes: it answers cancelled even when no job had that id. An auto-save that has not been sent yet is dropped, so cancel only when you really do not want it delivered.

`workEnqueueOnline` bridge#

window.WebToApk.workEnqueueOnline(id: String, url: String, method: String, headersJson: String, payload: String)

No permission needed; results echo as `appmint:work` / window.onAppMintWork.

Described by its group, Background jobs (WorkManager): durable auto-save + periodic native sync, rather than on its own.

Example

Hands one HTTP request to Android to send when the phone is online - even if the user closes the app or restarts the phone. Use it for a reliable auto-save.

Returns: nothing directly. The answer comes as the appmint:work event (and window.onAppMintWork(detail) if you define it): { id, status: 'enqueued' }, or { id, status: 'failed', reason } with reason invalid_arguments (empty id or a URL not starting with http) or enqueue_failed. Needs: nothing.

Durable auto-save: the same id replaces a save that has not been sent yet, so the newest state wins.

function autoSave(state, token) {
  if (!(window.WebToApk && window.WebToApk.workEnqueueOnline)) {
    showMessage('Offline auto-save works in the installed app only.');
    return;
  }
  WebToApk.workEnqueueOnline(
    'autosave',                                        // your job id
    'https://api.example.com/save',                    // http(s) URL
    'POST',                                            // POST | PUT | GET ...
    JSON.stringify({ Authorization: 'Bearer ' + token }), // headers as a JSON string
    JSON.stringify(state)                              // body as a string ('' for none)
  );
}

window.addEventListener('appmint:work', function (e) {
  const d = e.detail;
  if (d.id !== 'autosave') return;
  if (d.status === 'enqueued') showSavedBadge('Will sync when online');
  if (d.status === 'failed') showMessage('Could not queue the save: ' + d.reason);
});

Queue every form submission as its own job (a unique id per submission, so a second one does not replace the first) and wait for Android's answer:

function queueFeedback(form) {
  return new Promise(function (resolve, reject) {
    if (!(window.WebToApk && window.WebToApk.workEnqueueOnline)) {
      reject(new Error('not_in_app'));
      return;
    }
    const id = 'feedback-' + Date.now();
    function onWork(e) {
      if (e.detail.id !== id) return;                  // another job's answer
      window.removeEventListener('appmint:work', onWork);
      if (e.detail.status === 'enqueued') resolve(id);
      else reject(new Error(e.detail.reason));         // invalid_arguments | enqueue_failed
    }
    window.addEventListener('appmint:work', onWork);
    WebToApk.workEnqueueOnline(id, 'https://api.example.com/feedback', 'POST', '{}',
      JSON.stringify({ rating: form.rating.value, text: form.text.value }));
  });
}

Save a note as plain text with PUT; setting your own Content-Type stops the JSON default from being added:

function saveNote(noteId, text) {
  if (!(window.WebToApk && window.WebToApk.workEnqueueOnline)) return;
  WebToApk.workEnqueueOnline(
    'note-' + noteId,                                  // same note, same id: only the newest text is sent
    'https://api.example.com/notes/' + encodeURIComponent(noteId),
    'PUT',
    JSON.stringify({ 'Content-Type': 'text/plain; charset=utf-8' }),
    text
  );
}

document.getElementById('note').addEventListener('change', function (e) {
  saveNote(e.target.dataset.noteId, e.target.value);
});

Notes: enqueued means Android accepted the job, not that the server got it; there is no event when it is delivered. Delivery rules: a 2xx reply finishes the job; a 4xx reply stops it (no retry); a network error or 5xx retries with growing delays, up to 8 tries. Content-Type: application/json is added unless you set one. A GET sends no body. The page's JavaScript does not run in the background - only this native request does.

`workList` bridge#

window.WebToApk.workList(requestId: String)

No permission needed; results echo as `appmint:work` / window.onAppMintWork.

Described by its group, Background jobs (WorkManager): durable auto-save + periodic native sync, rather than on its own.

Example

Lists the background jobs this app has queued or scheduled.

Returns: nothing directly. The appmint:work event (and window.onAppMintWork) answers { requestId, jobs: [{ id, periodic, url, createdAt, pendingDelivery }] }. pendingDelivery is true while a one-off job has not been delivered yet (and always for a periodic job). Needs: nothing.

A small Promise wrapper that matches the answer by requestId:

function listJobs() {
  return new Promise(function (resolve) {
    if (!(window.WebToApk && window.WebToApk.workList)) { resolve([]); return; }
    const requestId = 'jobs-' + Date.now();
    function onWork(e) {
      if (String(e.detail.requestId) !== requestId) return;   // not our answer
      window.removeEventListener('appmint:work', onWork);
      resolve(e.detail.jobs || []);
    }
    window.addEventListener('appmint:work', onWork);
    WebToApk.workList(requestId);
  });
}

listJobs().then(function (jobs) {
  const unsent = jobs.filter(function (j) { return !j.periodic && j.pendingDelivery; });
  document.getElementById('unsent').textContent =
    unsent.length ? unsent.length + ' change(s) waiting for network' : 'All changes saved';
});

Show every job on a settings screen, with when it was queued:

window.addEventListener('appmint:work', function (e) {
  if (e.detail.requestId !== 'settings-jobs') return;
  const list = document.getElementById('jobs');
  list.innerHTML = '';
  (e.detail.jobs || []).forEach(function (job) {
    const li = document.createElement('li');
    li.textContent = job.id + (job.periodic ? ' (repeats)' : job.pendingDelivery ? ' (waiting)' : '') +
      ' - since ' + new Date(job.createdAt).toLocaleString();
    list.appendChild(li);
  });
});

if (window.WebToApk && window.WebToApk.workList) WebToApk.workList('settings-jobs');

When the app opens, set a "Background sync" switch from whether the repeating 'sync' job is still registered:

window.addEventListener('appmint:work', function (e) {
  if (e.detail.requestId !== 'startup') return;
  const on = (e.detail.jobs || []).some(function (j) { return j.id === 'sync' && j.periodic; });
  document.getElementById('sync-toggle').checked = on;
});

document.addEventListener('DOMContentLoaded', function () {
  if (window.WebToApk && window.WebToApk.workList) WebToApk.workList('startup');
});

Notes: a one-off job leaves the list once it is delivered, rejected with a 4xx, or given up after 8 tries. A numeric requestId may come back as a number, so compare with String(...).

`workSchedulePeriodic` bridge#

window.WebToApk.workSchedulePeriodic(id: String, url: String, method: String, headersJson: String, payload: String, intervalMinutes: Int)

No permission needed; results echo as `appmint:work` / window.onAppMintWork.

Described by its group, Background jobs (WorkManager): durable auto-save + periodic native sync, rather than on its own.

Example

Schedules a repeating HTTP request that Android sends in the background (when online), even while the app is closed. Good for a sync trigger or a heartbeat.

Returns: nothing directly. The answer comes as the appmint:work event (and window.onAppMintWork(detail)): { id, status: 'scheduled', intervalMinutes }, or { id, status: 'failed', reason } with reason invalid_arguments or schedule_failed. Needs: nothing.

function startBackgroundSync(userId) {
  if (!(window.WebToApk && window.WebToApk.workSchedulePeriodic)) {
    showMessage('Background sync works in the installed app only.');
    return;
  }
  WebToApk.workSchedulePeriodic(
    'sync',                                   // job id (scheduling again updates it)
    'https://api.example.com/sync',
    'POST',
    JSON.stringify({ 'X-User': userId }),     // headers as a JSON string
    JSON.stringify({ userId: userId }),       // the same body is sent every time
    30                                        // minutes; values under 15 become 15
  );
}

// Optional page hook instead of addEventListener:
window.onAppMintWork = function (d) {
  if (d.id === 'sync' && d.status === 'scheduled') {
    console.log('sync every', d.intervalMinutes, 'minutes');
  }
  if (d.status === 'failed') console.warn('job', d.id, 'failed:', d.reason);
};

A once-an-hour heartbeat: a GET sends no body, so pass an empty string, and '{}' when you need no headers:

function startHeartbeat(deviceId) {
  if (!(window.WebToApk && window.WebToApk.workSchedulePeriodic)) return;
  WebToApk.workSchedulePeriodic(
    'heartbeat',
    'https://api.example.com/ping?device=' + encodeURIComponent(deviceId),
    'GET',
    '{}',
    '',
    60
  );
}

Let the user pick how often to sync, and show the interval Android actually uses (anything under 15 comes back as 15):

document.getElementById('sync-every').addEventListener('change', function (e) {
  if (!(window.WebToApk && window.WebToApk.workSchedulePeriodic)) return;
  const minutes = parseInt(e.target.value, 10);        // e.g. 5, 30, 120
  WebToApk.workSchedulePeriodic('sync', 'https://api.example.com/sync', 'POST', '{}',
    JSON.stringify({ reason: 'periodic' }), minutes);  // same id: updates the existing job
});

window.addEventListener('appmint:work', function (e) {
  const d = e.detail;
  if (d.id !== 'sync') return;
  if (d.status === 'scheduled') {
    document.getElementById('sync-note').textContent = 'Syncing about every ' + d.intervalMinutes + ' minutes';
  } else if (d.status === 'failed') {
    document.getElementById('sync-note').textContent = 'Could not schedule sync (' + d.reason + ')';
  }
});

Notes: Android decides the exact moment; 15 minutes is the shortest interval, and battery saving can delay runs. The body is fixed when you schedule; to change it, schedule again with the same id. A 4xx reply does not cancel a periodic job; the next run tries again. Stop it with workCancel('sync').

workCancel bridge#

workEnqueueOnline bridge#

workList bridge#

workSchedulePeriodic bridge#

`workCancel` bridge#

`workEnqueueOnline` bridge#

`workList` bridge#

`workSchedulePeriodic` bridge#