selects only return partial result

Question

I have around 24k of rows in mysql database. Now using nodejs I would like to query and then store it in json file.

var fs = require('fs');
var mysql = require('mysql');
var connection = mysql.createConnection({
    host : '10.1.1.2',
    user : 'xxx',
    password : 'xxx',
    database : 'xxx'

});

connection.connect();
var json = '';
var query = 'SELECT * FROM st_training  GROUP BY EndDate ORDER BY StartDate DESC';
var query2 =  'SELECT * FROM st_training WHERE EmployeeID=901 GROUP BY EndDate ORDER BY StartDate DESC'; 
connection.query(query, function(err, results) {
if (err)  { throw err;
}

else {
jsonV = JSON.stringify(results);
console.log(jsonV);

 fs.writeFile('table.json', JSON.stringify(results), function (err) {

  if (err) throw err;
  console.log('Saved!');
});
 }
 connection.end();

  });

I can verify only partial around 600 rows being saved from console.log(jsonV) output or in table.json file. What could go wrong here? is it there is a max limitation for JSON.stringify ?