I am trying to export one or many records from a panel to an Excel template. To date I can only export a selected record but I want to improve this part. I've tried it but I can not find it.
My code ExtJS:

var prevFnExcel = function(grid, store, selModel){
        var parameters = store.data.keys.toString();
        var url = ctx + '/facturas.do?op=exportarExcel&idsFacturas=' + parameters;

        Ext.DomHelper.append(document.body, {
            tag: 'iframe',
            frameBorder: 0,
            width: 0,
            height: 0,
            css: 'display:none;visibility:hidden;height:0px;',                       
            src: url
     return false;