I have local var (Array list) which has three key, value pairs.

I want the second value to be displayed in the combo box and its key as default.

Code:
Ext.onReady(function(){

var group = [['brand', 'Product'],['site', 'Location'],['environment', 'Environment']];
    Ext.QuickTips.init();

    var store = new Ext.data.ArrayStore({
        fields: ['abbr', 'group'],
        data : group
    });
    var combo = new Ext.form.ComboBox({
        store: store,
        displayField:'group',
        typeAhead: true,
        mode: 'local',
        forceSelection: true,
        triggerAction: 'all',
        emptyText:'Location', //So the 'Location' which is second value is to be displayed. And its key 'site' 
        selectOnFocus:true,   
        applyTo: 'local-states'
    });
    combo.selectByValue('site', true); 
});