Create JSON from google sheets

createJSON.gs

function exportSheetAsJSON() {
  var sheet = SpreadsheetApp.getActiveSheet();
  var rows = sheet.getDataRange();
  var numRows = rows.getNumRows();
  var numCols = rows.getNumColumns();
  var values = rows.getValues();

  var output = "";
  output += "{\""+sheet.getName()+"\" : {\n";
  var header = values[0];
  for (var i = 1; i < numRows; i++) {
    if (i > 1) output += " , \n";
    var row = values[i];
    output += "\""+row[0]+"\" : {";
    for (var a = 1;a<numCols;a++){
      if (a > 1) output += " , ";
         output += "\""+header[a]+"\" : \""+row[a]+"\"";
    }
    output += "}";
    //Logger.log(row);
  }
  output += "\n}}";
  Logger.log(output);

  DriveApp.createFile(sheet.getName()+".json", output, MimeType.PLAIN_TEXT);

};

{nameOfSheet:
{first column:
{first row : second row}