convert my json object to csv downloadable file using jquery or javascript?

I have also gone through the similar requirements and I have used following code which is working good enough for me.
You can place the following code in a separate js file and link that file to your page.

/**
@namespace Converts JSON to CSV.
Compress with: http://jscompress.com/
*/
(function (window) {
    "use strict";
    /**
    Default constructor
    */
    var _CSV = function (JSONData) {
        if (typeof JSONData === 'undefined')
            return;

        var csvData = typeof JSONData != 'object' ? JSON.parse(settings.JSONData) : JSONData,
            csvHeaders,
            csvEncoding = 'data:text/csv;charset=utf-8,',
            csvOutput = "",
            csvRows = [],
            BREAK = '\r\n',
            DELIMITER = ',',
	    FILENAME = "export.csv";

        // Get and Write the headers
        csvHeaders = Object.keys(csvData[0]);
        csvOutput += csvHeaders.join(',') + BREAK;

        for (var i = 0; i < csvData.length; i++) {
            var rowElements = [];
            for(var k = 0; k < csvHeaders.length; k++) {
                rowElements.push(csvData[i][csvHeaders[k]]);
            } // Write the row array based on the headers
            csvRows.push(rowElements.join(DELIMITER));
        }
        csvOutput += csvRows.join(BREAK);
        // Initiate Download
        var a = document.createElement("a");

        if (navigator.msSaveBlob) { // IE10
            navigator.msSaveBlob(new Blob([csvOutput], { type: "text/csv" }), FILENAME);
        } else if ('download' in a) { //html5 A[download]
            a.href = csvEncoding + encodeURIComponent(csvOutput);
            a.download = FILENAME;
            document.body.appendChild(a);
            setTimeout(function() {
                a.click();
                document.body.removeChild(a);
            }, 66);
        } else if (document.execCommand) { // Other version of IE
            var oWin = window.open("about:blank", "_blank");
            oWin.document.write(csvOutput);
            oWin.document.close();
            oWin.document.execCommand('SaveAs', true, FILENAME);
            oWin.close();
        } else {
            alert("Support for your specific browser hasn't been created yet, please check back later.");
        }
    };
    window.CSVExport = _CSV;
})(window);

Then for the utilization of above code you can just pass your json in the object as shown in the following code

//you can fetch your json in the following variable from ajax request,then just need to pass it in the CSVExport as shown
var yourjson = [{Name: "umer", Id: 1}, 
                  {Name: "khalid", Id: 2}, 
                  {Name: "etc", Id: 3}];

   var x = new CSVExport(yourjson);