App Script to create a JSON from google spreadsheet

createJSON.js

function doGet(e) {
 
    var json = convertSheet2JsonText();
    return ContentService.createTextOutput(JSON.stringify(json))
    .setMimeType(ContentService.MimeType.JSON);

}
function convertSheet2JsonText() {
 //XXXX is the id of the spreadsheet.ID is in the spreadsheet url - docs.google.com/spreadsheets/d/XXXX/editkkkk
  var sheet = SpreadsheetApp.openById("XXXX").getActiveSheet();
  var colStartIndex = 1;
  var rowNum = 1;
  var firstRange = sheet.getRange(1, 1, 1, sheet.getLastColumn());
  var firstRowValues = firstRange.getValues();
  var titleColumns = firstRowValues[0];
  
  // after the second line(data)
  var lastRow = sheet.getLastRow();
  var rowValues = [];
  for(var rowIndex=2; rowIndex<=lastRow; rowIndex++) {
    var colStartIndex = 1;
    var rowNum = 1;
    var range = sheet.getRange(rowIndex, colStartIndex, rowNum, sheet.getLastColumn());
    var values = range.getValues();
  
    rowValues.push(values[0]);
  }
 
  // create json
  var jsonArray = [];
  for(var i=0; i<rowValues.length; i++) {
    var line = rowValues[i];
    var json = new Object();
    for(var j=0; j<titleColumns.length; j++) {
      json[titleColumns[j]] = line[j];
    }
    jsonArray.push(json);
  }
  return jsonArray ;
}

When the above code is published, google will provide a URL. When the URL is called it will return a JSON.