DataStore.sync()

The sync() method of the DataStore interface opens a cursor that allows you to step through any changes that have taken place in the data store going back to a particular revision ID, and run code in response to different types of change.

Syntax

var cursor = stores[0].sync(3);

Returns

A DataStoreCursor object.

Parameters

revisionId Optional

You can optionally pass sync() a revision ID that specifies the place in the revision history to go back to when running through the tasks. If you don't specify this, it runs through all tasks going back to the beginning of the history.

Example

In the following example, we create a cursor using sync(), then invoke the runNextTask() function to run the next task in the cursor. In this function, the DataStoreCursor.next method is used to retrieve the next task (a DataStoreTask object), then the manageTask() function checks what type of task it is, and takes action accordingly. In this case, we are either done running through the tasks, in which case we return, or the task is an addition, in which case we run a function to display that addition in the app UI then move on to the next task by running runNextTask() again.

var cursor = stores[0].sync();
runNextTask(cursor);

function runNextTask(cursor) {
 cursor.next().then(function(task) {
   manageTask(cursor, task);
 });
}

function manageTask(cursor, task) {
  if (task.operation == 'done') {
    // Finished adding contacts!
    return;
  }

  if (task.operation == 'add') {
    // Add the contacts that are different to how it was before
    displayExisting(task.id, task.data);
  }

  runNextTask(cursor);
}

Specifications

The discussion concerning this API's creation happened in various Mozilla mailing lists and other places. A summary of the discussion and further pointers can be found on the Mozilla Wiki. For further feedback and questions, send mail to the dev-webapi mailing list.

Browser compatibility

See also

• Using the Data Store API
• Data Store Contacts Editor example
• Data Store Contacts Viewer example