в четверке эт делалось так:
<html>
<head>
<link href="http://docs.sencha.com/extjs/4.2.2/extjs-build/resources/css/ext-all-gray-debug.css" rel="stylesheet"/>
<script src="http://docs.sencha.com/extjs/4.2.2/extjs-build/ext-all.js"></script>
<script>
var myStore = Ext.create('Ext.data.Store', {
fields: ['id', 'data'],
data: [{
id: 1, data: 'data 1'
}, {
id: 2, data: 'data 2'
}]
});
console.log(myStore.getCount());
console.log(myStore.getAt(0).get('data'));
console.log(myStore.getAt(1).get('data'));
</script>
</head>
<body></body>
</html>