Cannot require a class in NodeJs? - node.js

Question

I have two files:
mysqlDAOFactory.js:
var mysql = require('mysql');
var mysqlUserDAO = require('./mysqlUserDAO');
var mysqlSessionDAO = require('./mysqlSessionDAO');
class mysqlDAOFactory {
static createConnection() {
var connection = mysql.createConnection({
host:'localhost',
user:'root',
password:'',
database:'QASys'
});
return connection;
}
static getDbInstance() {
return mysql;
}
getUserDAO() {
return new mysqlUserDAO();
}
getSessionDAO() {
return new mysqlSessionDAO();
}
}
module.exports = mysqlDAOFactory;
mysqlUserDAO.js:
var mysqlDAOFactory = require('./mysqlDAOFactory.js');
var bcrypt = require('bcryptjs');
var preparedStatements = require('./preparedStatements');
class mysqlUserDAO {
constructor() {
this.connection = mysqlDAOFactory.createConnection();
this.mysql = mysqlDAOFactory.getDbInstance();
}
}
module.exports = mysqlUserDAO;
When I run the file test.js:
var mysqlDAOFactory = require('./mysqlDAOFactory.js');
var UserDAO = mysqlDAOFactory.getUserDAO();
the program is not recognize the variable mysqlDAOFactory in the constructor of class in mysqlUserDAO.js although I require this variable before.
Can anyone explain to me why this happened?
results in chrome debugger tool

Answer 1

I have reviewed your cod and you made a mistake of circular dependencies due to that you fail to run a code.
I have temporary comment mysqlSession file because you did not post MySQL session file.
Please see the running example then please review link as well.
https://repl.it/#DipakC/SO-50542396cannot-require-a-class-in-nodejs
test.js:
//var mysqlDAOFactory = require('./mysqlDAOFactory');
const mysqlUserDAO = require("./mysqlUserDAO");
let objMysqlUserDAO = new mysqlUserDAO();
console.log("---- ---- ----");
console.log(objMysqlUserDAO);
console.log("---- ---- ----");
mysqlUserDAO.js
var mysqlDAOFactory = require('./mysqlDAOFactory');
var bcrypt = require('bcryptjs');
class mysqlUserDAO {
constructor() {
this.connection = mysqlDAOFactory.createConnection();
this.mysql = mysqlDAOFactory.getDbInstance();
}
}
module.exports = mysqlUserDAO;
mysqlDAOFactory.js
var mysql = require('mysql');
var mysqlUserDAO = require('./mysqlUserDAO');
//var mysqlSessionDAO = require('./mysqlSessionDAO');
class mysqlDAOFactory {
static createConnection() {
var connection = mysql.createConnection({
host:'localhost',
user:'root',
password:'',
database:'QASys'
});
return connection;
}
static getDbInstance() {
return mysql;
}
static getUserDAO() {
return new mysqlUserDAO();
}
/* getSessionDAO() {
return new mysqlSessionDAO();
} */
}
module.exports = mysqlDAOFactory;