title: Populate ComboBox ExtJS 4.2 using JSON
body: <p>I have to populate a ComboBox in ExtJS 4.2 using JSON data received from a php.
  Code so far :
  DataStore:</p>
  
  <pre><code>var Cstates = new Ext.data.Store({
      autoLoad: true,
      url: 'data.php',
      storeId: 'Cstates',
      reader: new Ext.data.JsonReader({
          root: 'state'
      }),
      idProperty: 'abbr',
      fields: ['abbr', 'name']
  });
  </code></pre>
  
  <p>ComboBox:</p>
  
  <pre><code>{
      xtype: 'combo',
      id: 'cmbState',
      fieldLabel: ' Select state :',
      triggerAction: 'all',
      store: Cstates,
      queryMode: 'local',
      valueField: 'abbr',
      displayField: 'name',
      triggerAction: 'all',
      typeAhead: true,
      emptyText: '* All States',
      forceSelection: true,
      selectOnFocus: true,
      allowBlank: false,
      selectOnTab: true,
      //hidden: true,
      disabled: true
  }
  </code></pre>
  
  <p>JSON received:</p>
  
  <pre><code>{state:[{"abbr":"E1","name":"EAST1"},{"abbr":"E2","name":"EAST2"}]}
  </code></pre>
  
  <p>Also later I need to populate this combobox with some other value that will be returned in the same format from a php using GET ie data.php?region=EAST.</p>