sencha touch json store

js:

Ext.define('MyApp.store.MyJsonStore', {
    extend: 'Ext.data.Store',

    requires: [
        'MyApp.model.Person',
        'Ext.data.proxy.Ajax',
        'Ext.data.reader.Json'
    ],

    config: {
        autoLoad: true,
        data: [
            {
                id: 909,
                firstName: 'Anthony',
                lastName: 'Hill'
            }
        ],
        groupField: 'lastName',
        model: 'MyApp.model.Person',
        storeId: 'MyJsonStore',
        proxy: {
            type: 'ajax',
            url: '/a.js',
            reader: {
                type: 'json'
            }
        }
    }
});

json from server:

[
    { id: 1, firstName: 'Tommy laptop', lastName: 'Maintz' },
    { id: 2, firstName: 'Rob', lastName: 'Dougan' },
    { id: 3, firstName: 'Ed', lastName: 'Avins' },
    { id: 4, firstName: 'Jamie laptop', lastName: 'Avins' },
    { id: 5, firstName: 'Dave', lastName: 'Dougan' },
    { id: 6, firstName: 'Abraham', lastName: 'Elias' },
    { id: 7, firstName: 'Jacky', lastName: 'Ngyuyen' },
    { id: 8, firstName: 'Jay', lastName: 'Ngyuyen' },
    { id: 9, firstName: 'Jay', lastName: 'Robinson' },
    { id: 10, firstName: 'Rob', lastName: 'Avins' },
    { id: 11, firstName: 'Ed', lastName: 'Dougan' },
    { id: 12, firstName: 'Jamie', lastName: 'Poulden' },
    { id: 13, firstName: 'Dave', lastName: 'Spencer' },
    { id: 14, firstName: 'Abraham', lastName: 'Avins' },
    { id: 15, firstName: 'Jacky', lastName: 'Avins' },
    { id: 16, firstName: 'Rob', lastName: 'Kaneda' },
    { id: 17, firstName: 'Ed', lastName: 'Elias' },
    { id: 18, firstName: 'Tommy', lastName: 'Dougan' },
    { id: 19, firstName: 'Rob', lastName: 'Robinson' }
]