extJs Alert Help

Question

var encClinic = new Ext.chart.StackedBarChart({
    store: new Ext.data.Store({
        reader:encReader,
        url:data.jsonUrl,
        baseParams:{
            cmd:'OHMjson.Graph',
            graphName:'ENC',
            graphType:'Clinics'
        }
    }),
    yField: 'CLINIC',
    xAxis: new Ext.chart.NumericAxis({
        stackingEnabled: true,
        title: text.occurrences
    })
});

1. I am displaying some values here, i need to debug by displaying an alert here whether the data retrieved are correct or not.

2. Can anyone explain me the code too.