The source code

    /*!
     * Ext JS Library 3.4.0
     * Copyright(c) 2006-2011 Sencha Inc.
     * licensing@sencha.com
     * http://www.sencha.com/license
     */
    /**
     * @class Ext.data.JsonStore
     * @extends Ext.data.Store
     * Small helper class to make creating {@link Ext.data.Store}s from JSON data easier.
     * A JsonStore will be automatically configured with a {@link Ext.data.JsonReader}.
     * A store configuration would be something like:
    var store = new Ext.data.JsonStore({
        // store configs
        autoDestroy: true,
        url: 'get-images.php',
        storeId: 'myStore',
        // reader configs
        root: 'images',
        idProperty: 'name',
        fields: ['name', 'url', {name:'size', type: 'float'}, {name:'lastmod', type:'date'}]
    });
     *
     * This store is configured to consume a returned object of the form:
    {
        images: [
            {name: 'Image one', url:'/GetImage.php?id=1', size:46.5, lastmod: new Date(2007, 10, 29)},
            {name: 'Image Two', url:'/GetImage.php?id=2', size:43.2, lastmod: new Date(2007, 10, 30)}
        ]
    }
     *
     * An object literal of this form could also be used as the {@link #data} config option.
     * *Note: Although not listed here, this class accepts all of the configuration options of
     * {@link Ext.data.JsonReader JsonReader}.
     * @constructor
     * @param {Object} config
     * @xtype jsonstore
     */
    Ext.data.JsonStore = Ext.extend(Ext.data.Store, {
        /**
         * @cfg {Ext.data.DataReader} reader @hide
         */
        constructor: function(config){
            Ext.data.JsonStore.superclass.constructor.call(this, Ext.apply(config, {
                reader: new Ext.data.JsonReader(config)
            }));
        }
    });
    Ext.reg('jsonstore', Ext.data.JsonStore);