The id read-only property of the DataStoreChangeEvent interface returns the identifier of the changed record in the data store. This must return null if the operation is cleared.

Note: The Data Store API is available in Web Workers, from Firefox 32 onwards


myId =;


A DataStoreKey.


In the following snippet we retrieve all the data stores on the device with the name "contacts", then we use DataStore.sync to create a cursor to use for syncing the app with the current "content" data store (displaying new items, etc.) This cursor is passed to the runNextTask() function that will deal with running through the updates in some way. Next, we include some code inside an onchange function so that when a change is made we return the DataStoreChangeEvent (e in this case), find out what type of task the change was, and then take action based on this type (either adding or deleting a contact's information.)

The deleteContact() and loadContact() functions are passed to use in their functionality.

navigator.getDataStores('contacts').then(function(stores) {
  var cursor = stores[0].sync();

  stores[0].onchange = function(e) {
    if (e.operation == 'removed') {
      // Delete the contact

    if (e.operation == 'added') {
      stores[0].get( {
        // Add the new contact