ASP.NET gridview to JSON - asp.net

Question

So I am looking at converting a GridView (with data from an Oracle database) to JSON file, which is then used in Highcharts chart.
So far, I have Newtonsoft.JSON and have seen multiple tutorials with converting datatables to JSON, but am unable to get gridview to JSON (see How to convert gridview data to Json? for reference to code I have).
<script src="~/Scripts/jquery.base64.js"></script>
<script src="~/Scripts/tableExport.js"></script>
<script src="~/Scripts/jspdf/libs/base64.js"></script>
<script src="~/Scripts/jspdf/jspdf.js"></script>
<script src="~/Scripts/jspdf/FileSaver.js"></script>
<script src="~/Scripts/jspdf/jspdf.plugin.cell.js"></script>
function ExportTpGridtoPDF(divid) {
var table1 =
tableToJson($('#' + divid + ' .grid-table').get(0)),
cellWidth = 35,
rowCount = 0,
cellContents,
leftMargin = 10,
topMargin = 15,
topMarginTable = 5,
headerRowHeight = 13,
rowHeight = 13,
l = {
orientation: 'l',
unit: 'mm',
format: 'a3',
compress: true,
fontSize: 8,
lineHeight: 1,
autoSize: false,
printHeaders: true
};
var doc = new jsPDF(l, '', '', '');
doc.setProperties({
title: 'Test PDF Document',
subject: 'This is the subject',
author: 'author',
keywords: 'generated, javascript, web 2.0, ajax',
creator: 'author'
});
doc.cellInitialize();
$.each(table1, function (i, row) {
rowCount++;
$.each(row, function (j, cellContent) {
if (rowCount == 1) {
doc.margins = 1;
doc.setFontSize(12);
doc.cell(leftMargin, topMargin, cellWidth, headerRowHeight, cellContent, i)
}
else if (rowCount == 2) {
doc.margins = 1;
doc.setFontSize(12);
doc.cell(leftMargin, topMargin, cellWidth, rowHeight, cellContent, i);
}
else {
doc.margins = 1;
doc.setFontSize(12);
doc.cell(leftMargin, topMargin, cellWidth, rowHeight, cellContent, i);
}
})
})
doc.save('sample Report.pdf');
}
function tableToJson(table) {
var data = [];
// first row needs to be headers
var headers = [];
for (var i = 0; i < table.rows[0].cells.length; i++) {
if (table.rows[0].cells[i].innerHTML != "") {
headers[i] = table.rows[0].cells[i].innerText.toLowerCase().replace(/ /gi, '');
}
}
// go through cells
for (var i = 1; i < table.rows.length; i++) {
var tableRow = table.rows[i];
var rowData = {};
for (var j = 1; j < tableRow.cells.length; j++) {
rowData[headers[j]] = tableRow.cells[j].innerText;
}
data.push(rowData);
}
return data;
}