ExtJS Template

HTML

<link rel="stylesheet" href="//extjs.cachefly.net/ext-4.1.0-gpl/resources/css/ext-all-gray-debug.css" />
<script src="//extjs.cachefly.net/ext-4.1.0-gpl/ext-all-dev.js"></script>

JavaScript

/* this is a function to simulate ajax requests in jsfiddle */

function sim(proxy, data, delay) {
    if (typeof data !== 'string') {
        data = Ext.JSON.encode(data);
    }

    proxy.url = '/echo/json/';
    proxy.actionMethods.read = "POST";
    proxy.extraParams.json = data;
    proxy.extraParams.delay = typeof delay == 'undefined' ? 0 : delay;
}

Ext.define('Store1', {
    extend: 'Ext.data.Store',
    fields: ['name'],
    remoteSort: false,
    proxy: {
        type: 'ajax',
        url: 'whatever',
        reader: {
            type: 'json',
            root: 'data'
        }
    }
});

var s = new Store1();

Ext.util.Observable.capture(s, function() {
    console.log(arguments);
});

sim(s.proxy, [
    {
    name: 'a'},
{
    name: 'b'},
{
    name: 'c'},
{
    name: 'd'},
{
    name: 'e'},
{
    name: 'f'},
{
    name: 'g'},
{
    name: 'h'},
{
    name: 'i'},
{
    name: 'j'},
{
    name: 'k'},
{
    name: 'l'},
{
    name: 'm'},
{
    name: 'n'},
{
    name: 'o'},
{
    name: 'p'},
{
    name: 'q'},
{
    name: 'r'},
{
    name: 's'},
{
    name: 't'},
{
    name: 'u'},
{
    name: 'v'},
{
    name: 'w'},
{
    name: 'x'},
{
    name: 'y'},
{
    name: 'z'},
{
    name: 'a'},
{
    name: 'b'},
{
    name: 'c'},
{
    name: 'd'},
{
    name: 'e'},
{
    name: 'f'},
{
    name: 'g'},
{
    name: 'h'},
{
    name: 'i'},
{
    name: 'j'},
{
    name: 'k'},
{
    name: 'l'},
{
    name: 'm'},
{
    name: 'n'},
{
    name: 'o'},
{
    name: 'p'},
{
    name: 'q'},
{
    name: 'r'},
{
    name: 's'},
{
    name: 't'},
{
    name: 'u'},
{
    name: 'v'},
{
    name: 'w'},
{
    name: 'x'},
{
    name: 'y'},
{
    name: 'z'},
{
    name: 'a'},
{
    name: 'b'},
{
    name: 'c'},
{
    name: 'd'},
{
    name: 'e'},
{
    name: 'f'},
{
    name: 'g'},
{
    name: 'h'},
{
    name: 'i'},
{
    name: 'j'},
{
    name: 'k'},
{
    name: 'l'},
{
    name: 'm'},
{
    name: 'n'},
{
    name: 'o'},
{
    name: 'p'},
{
    name: 'q'},
{
    name: 'r'},
{
    name:...