Extjs4.2 json data

HTML

<link rel="stylesheet" href="http://cdn.sencha.com/ext/gpl/4.2.0/resources/css/ext-all.css">
<div id="testdiv"></div>

JavaScript

Ext.onReady(function(){

    var data = [{"ID":1,"Name":"aa","Category":"A","Price":200.00}, {"ID":2,"Name":"bb","Category":"B","Price":200.00},
 {"ID":3,"Name":"cc","Category":"C","Price":200.00},
 {"ID":4,"Name":"dd","Category":"D","Price":200.00},
 {"ID":5,"Name":"ee","Category":"E","Price":200.00},
 {"ID":6,"Name":"ee","Category":"F","Price":200.00}]
    
    Ext.define('MyModel', {
        extend: 'Ext.data.Model',
        idProperty: 'ID',
        fields: [
            {name: 'ID'},
            {name: 'Category'},
            {name: 'Price'}
        ]
    });
    
    var store = Ext.create('Ext.data.Store', {
        autoLoad: true,
        data : data,
        model: 'MyModel',
        proxy: {
            type: 'memory',
            reader: {
                type: 'json',
            }
        }
    });
    
    Ext.create('Ext.Panel', {
        id: 'test',
        width: 960,
        height:600,
              renderTo: 'testdiv',
        layout: 'vbox',
        items: [
           {
              xtype: 'grid',
              title: 'hello',
              height: 400,
              width: 700,
              store: store,
              columns: [
                  {
                     text: 'column1',
                     dataIndex: 'ID'
                  },{
                     text: 'column2',
                     dataIndex: 'Category'
                  },{
                     text: 'column3',
                     dataIndex: 'Price'
                  }
              ]
           }
        ]
    });
    
});