Knowing when originally initialized

[bradschafer]

How would it be possible to get a callback when the array is 'initialized'? (to the length of the snapshot when the request was made)

For example if you need to walk all the records in the list once it's initially 'synced'.
or proceed to the next function in a serialized startup routine.

[katowulf]

You would need a promise implementation like q or jQuery or Angular's $q. I'll use jQuery for now.

In the constructor, add:

this.loadFuture = $.Deferred();

Add a method:

loaded: function() {
    return this.loadFuture.promise();
}

And in initListeners:

    _initListeners: function() {
      this._monit('child_added', this._serverAdd);
      this._monit('child_removed', this._serverRemove);
      this._monit('child_changed', this._serverChange);
      this._monit('child_moved', this._serverMove);
      // guaranteed to be called after the previously established
      // event listeners are triggered
      var def = this._loadedFuture;
      this.ref.once('value', def.resolve, def.reject);
    },

The biggest hinderance to this (and why I didn't just throw it in when you asked) is picking a promise library and adding that as a dependency.