KTDatatable does not support the export feature. But you can use this plugin to export as a PDF. Integrate it to your custom export button, by passing the data into the PDF plugin. https://github.com/simonbengtsson/jsPDF-AutoTable
var data = datatable.getDataSet();
Call this function to get the current data in the grid.
I would suggest CSV more than excel, and I think the easier one is to create a CSV file. You can also learn more about CSV text format here;