B2G OS

DataStore.getLength()

This API is available on Firefox OS for internal applications only.

The getLength() method of the DataStore interface returns the number of records stored in the current data store.

Note: The Data Store API is available in Web Workers, from Firefox 32 onwards (Firefox OS 2.0; see bug 949325.)

Syntax

store.getLength().then(function(storeLength) {
  // Do something with storeLength
});

Returns

A Promise object of type unsigned long that resolves with a numeric variable containing the number of records stored in the current data store.

Example

In the following example, we use navigator.getDataStores to return a list of DataStore objects representing data stores on the device called contacts. Since there is only one such data store, we can access it inside the outer promise using stores[0]. The next promise uses DataStore.getLength to return the number of records in the store. If the value is 0, we populate the data store with records contained in the contactsInit object; if there is already data in the store, we run DataStore.sync to loop through any additions since the code last accessed the data store and update the data display as necessary.

navigator.getDataStores('contacts').then(function(stores) {
  stores[0].getLength().then(function(storeLength) {
    if(storeLength == 0) {
        for(i = 0; i < contactsInit.length; i++) {
        addContact(stores[0],contactsInit[i]);  
      };
    } else {
      var cursor = stores[0].sync();
      runNextTask(cursor);
    }
  });
});

Note: This code is taken from our Data Store Contacts Editor demo. Look through the code to help you understand better what is going on, and how the full code works.

Specifications

Specification Status Comment
Data Store API
The definition of 'getLength()' in that specification.
Draft  

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

Supported in Firefox OS 1.0.1.
Available in web workers in Firefox OS 2.0.

See also

Document Tags and Contributors

Contributors to this page: fscholz, chrisdavidmills
Last updated by: fscholz,