Node.js code to connect to mysql

mysql.js

var http = require("http");
var mysql = require("mysql");
var fs = require("fs");
var jsonContent = null;
const prompt = require('electron-prompt');
var userdata = {
  "host": '',
  "port": '',
  "username": '',
  "password": '',
  "database": ''
};

onLoad();

function onLoad() {
  // console.log("main window : " + mainWindow);
  var connection = null;
  try {
    
    //This will prompt user for Database details one time.
    var contents = fs.readFileSync(process.env.APPDATA + "/Mcare/sql-config.json");
    jsonContent = JSON.parse(contents);
    connection = mysql.createConnection({
      host: jsonContent.host,
      port: jsonContent.port,
      user: jsonContent.username,
      database: jsonContent.database,
      password: jsonContent.password,
      debug: false
    });
  } catch (ex) {
    var dummy = JSON.stringify(userdata);
    fs.writeFileSync(process.env.APPDATA + "/AngularElectronMySQL/sql-config.json", dummy);
    onLoad();
  }
  connection.connect(function (err) {
    if (err) {
      console.error("error connecting: " + err.stack);

      prompt({
          title: 'Sql Config',
          label: 'Host:',
          value: jsonContent.host,
          inputAttrs: {
            type: 'text'
          },
          type: 'input',
        })
        .then((h) => {
          if (h) {
            userdata.host = h;
            prompt({
                title: 'Sql Config',
                label: 'Port:',
                value: jsonContent.port,
                inputAttrs: {
                  type: 'text'
                },
                type: 'input',
              })
              .then((p) => {
                if (p) {
                  userdata.port = p;
                  prompt({
                      title: 'Sql Config',
                      label: 'Username:',
                      value: jsonContent.username,
                      inputAttrs: {
                        type: 'text'
                      },
                      type: 'input',
                    })
                    .then((u) => {
                      if (u) {
                        userdata.username = u;
                        prompt({
                            title: 'Sql Config',
                            label: 'Password:',
                            value: jsonContent.password,
                            inputAttrs: {
                              type: 'password'
                            },
                            type: 'input',
                          })
                          .then((w) => {
                            userdata.password = w;
                            prompt({
                                title: 'Sql Config',
                                label: 'Database:',
                                value: jsonContent.database,
                                inputAttrs: {
                                  type: 'text'
                                },
                                type: 'input',
                              })
                              .then((d) => {
                                if (d) {
                                  userdata.database = d;
                                  var json = JSON.stringify(userdata);
                                  fs.writeFileSync(process.env.APPDATA + "/Mcare/sql-config.json", json);
                                  onLoad();
                                }
                              })
                              .catch(console.error);
                          })
                          .catch(console.error);
                      }
                    })
                    .catch(console.error);
                }
              })
              .catch(console.error);
          }
        })
        .catch(console.error);
    } else {
      connection.end();
      console.log("connected as id " + connection.threadId);
      afterLoad();
    }
  });
}

function afterLoad() {
  http
    .createServer(function (req, res) {
      var taskQueue = [];
      var token = 0;
      
      function checkExecuteFinished(queue) {
        if (queue.length == 0) {
          res.setHeader("Content-Type", "application/json");
          res.write(JSON.stringify(data, null, 4));
          res.end();
        }
      }

      function readDataFromMySql(query, fn) {
        taskQueue.push(token++);
        var connection = mysql.createConnection({
          host: jsonContent.host,
          port: jsonContent.port,
          user: jsonContent.username,
          database: jsonContent.database,
          password: jsonContent.password,
          debug: false
        });
        connection.connect(function (err) {
          if (err) {
            console.error("error connecting: " + err.stack);
            return;
          }

          console.log("connected as id " + connection.threadId);
        });
        connection.query(query, function (error, results, fields) {
          if (error) throw error;
          fn(results);
          connection.end();
        });
      }

    var data = [];
      function cleanData() {
        data = {
          id: "",
          name: ""
        };
      }

    function getData(results) {
        for (var i = 0; i < results.length; i++) {
            cleanData();
            data.id = results[i].Id;
            data.name = results[i].Name;
          }
        }
        taskQueue.shift();
        checkExecuteFinished(taskQueue);
      }

      readDataFromMySql("select * from table", getData);

      // console.log(JSON.stringify(location));
    })
    .listen(1024);
}