Combined export of multiple grids to corresponding worksheets in a single workbook.

Following are the steps:

    var w1 = grid1.exportExcel({workbook: true});//export 1st grid into js workbook.
    var w2 = grid2.exportExcel({workbook: true});//export 2nd grid into js workbook.

    w1.sheets.push( w2.sheets[0] );//copy worksheet of 2nd workbook to 1st workbook.

    var blob = pq.excel.exportWb({workbook: w1, type: 'blob'});//export 1st workbook into Excel file.
    pq.saveAs(blob, "pqGrid.xlsx" );