custom mysql function in nodejs returns undefined

Question

so I have a multi function in a file in NodeJS, and it returns undefined, so here is my code: `

var MySql = require('mysql');

var mysql = MySql.createConnection({
    host: process.env.DB_IP,
    user: process.env.DB_USER,
    password: process.env.DB_PASS,
    database: "gamezone_3tar"
});

mysql.connect(function(err){
    if (err) throw err;
    console.log('MySql Connection Successfully!');
});

module.exports = {
    checkGuild: function(gid){
        var sql = "SELECT * FROM GUILDS WHERE `gid` = '"+gid+"'";
        mysql.query(sql, function (err, result) {
            if (err) throw err;
            return true;
        });
    },
    addGuild: function(gid, gname, gowner){
        var sql = "INSERT INTO GUILDS(`gid`, `gname`, `gOwner`) VALUES ('"+gid+"', '"+gname+"', '"+gowner+"')";
        mysql.query(sql, function (err, result) {
            if (err) throw err;
            return true;
        });
    },
    checkVip: function(type, id){
        if(type == 'guild')
            var sql = 'SELECT vip FROM GUILDS WHERE `gid` = ?';
        else if(type == 'user')
            var sql = 'SELECT vip FROM USERS WHERE `uid` = ?';
        
        mysql.query(sql, [id], function(err, result){
            if (err) throw err;
            var tempdata = JSON.parse(result);
            if(tempdata.vip == 'false') 
                return false;
            else if(tempdata.vip == 'true') 
                return true;
        });
    },
    addVip: function(type, id){
        if(type == 'guild')
            var sql = "UPDATE GUILDS SET vip = 'true' WHERE `gid` = '"+id+"'";
        else if(type == 'user')
            var sql = "UPDATE USERS SET vip = 'true' WHERE `uid` = '"+id+"'";
        
        mysql.query(sql, function(err, result){
            if (err) throw err;
            return true;
        });
    },
    removeVip: function(type, id){
        if(type == 'guild')
            var sql = "UPDATE GUILDS SET vip = 'false' WHERE `gid` = '"+id+"'";
        else if(type == 'user')
            var sql = "UPDATE USERS SET vip = 'false' WHERE `uid` = '"+id+"'";
        
        mysql.query(sql, function(err, result){
            if (err) throw err;
            return true;
        });
    },
    removeGuild: function(gid){
        var sql = "DELETE FROM GUILDS WHERE `gid` = '"+gid+"'";
        mysql.query(sql, function(err, result){
            if (err) throw err;
            return true;
        });
    }
};

and here is the discord bot command i use to trigger this functions:

var db = require('../../etc/database.js');

module.exports = {
  name: "addvip",
  description: "change guild to vip",
  execute(message) {
    const msgID = message.author.id;
    if (!admins.includes(msgID)) return;
    if(db.checkGuild(message.guild.id) == true)
    {
      if(db.checkVip('guild', message.guild.id) == true)
      {
        console.log('already vip!');
      }
      else if(db.checkVip('guild', message.guild.id) == false)
      {

        if(db.addVip('guild', message.guild.id) == true)
        {
          console.log('Guild is now vip!');
        }else{
          console.log('error in addvip');
        }

      }else{
        console.log('error in checkVip');
      }
    }
    else if(!db.checkGuild(message.guild.id) == true)
    {
      if(db.addGuild(message.guild.id, message.guild.name, message.guild.owner) == true)
      {
        if(db.addVip('guild', message.guild.id) == true)
        {
          console.log('added to vip!');
        }else console.log('error in adding [check]');
      }else console.log(db.addGuild(message.guild.id, message.guild.name, message.guild.owner));
    }else console.log('wtf!');
  }
};

so any idea how to fix this, please? I'm seriously working on this code like 1 month after solving SQL errors and...

and BTW, it successfully connects to MySQL server!

Answer 1

It seems to be due to the fact that your SQL code uses callbacks, so no data is immediately returned and therefore, the return value is undefined . To fix this, you need to make the SQL functions return a Promise and change the return statement to resolve() , like this:

checkGuild: function(gid){
    return new Promise(resolve => {
        var sql = "SELECT * FROM GUILDS WHERE `gid` = '"+gid+"'";
        mysql.query(sql, function (err, result) {
            if (err) throw err;
            resolve(true);
        });
    });
},

Then, you need to use await wherever the function is called in order to wait for the Promise to complete. Since, you are calling the functions in the addvip command file, you need to make the execute function asynchronous, so that you can use await :

module.exports = {
  name: "addvip",
  description: "change guild to vip",
  async execute(message) {
    const msgID = message.author.id;
    if (!admins.includes(msgID)) return;
    if(await db.checkGuild(message.guild.id) == true)