Hi Sarath,
Here is the code from the same example which you provided:
selectionChanged: function search(oEvent) {
var idx = oEvent.getParameter("newLeadSelectedIndex");
alert("Product '"+oDataSet.getItems()[idx].getTitle()+"' selected.'");
}
You need to use argument - oEvent and its method getParameter
More info - JsDoc Report - SAP UI development Toolkit for HTML5 - API Reference - sap.ui.ux3.DataSet