Generate new username available, always getting Undefined

Question

I have a function to generate an available username, but always return undefined. I tried in many ways, in this case is a recursive function, but I'm always getting the same result, can you help me? Thanks

This is the code:

function generateNewUsernameAvailable(userName, number){
  console.log('FUNCTION generateNewUsernameAvailable '+userName+' with number '+number);
  User.countDocuments({ 'userName' : userName+number }, (err, count) => {
    if (err) {
      return `Error: ${err}`;
    }
    if (count == 0) {
      return userName+number;
    }else{
      generateNewUsernameAvailable(userName, number+1);
    }});
}

module.exports.existsUserName = function(req,res){
  let userName = req.body.userName;
  console.log('POST existsUserName '+userName);
  User.countDocuments({ 'userName' : userName }, (err, count) => {
    if (err) {
      return res.status(500).send({message: `Error: ${err}`});
    }
    // Available
    if (count == 0){
      return res.status(200).send();
    } else {
      // Generate and return a new username available
      console.log(generateNewUsernameAvailable('ricardo', 1));
      res.status(400).send({message: 'newUsernameAvailable (Example ricardo1)'});
    }
  })
}

Possible duplicate of [How do I return the response from an asynchronous call?](https://stackoverflow.com/questions/14220321/how-do-i-return-the-response-from-an-asynchronous-call) — Arif Khan, Jul 31 '18 at 12:16

score 0 · Accepted Answer · answered Jul 31 '18 at 18:54

FindOne is faster than countDocuments/estimatedDocumentCount in this case. Both are promises, I'm going to add a possible solution:

function generateNewUsernameAvailable(userName, number){
  return User
  .findOne({ 'userName' : userName+number })
  .then(function(result){
    if (result){
      return generateNewUsernameAvailable(userName, number+1);
    }else{
      return userName+number;
    }
  })
  .catch(function(err) {
      console.log(`Error: ${err}`);
      throw err;
  });
}

module.exports.existsUserName = function(req,res){
  let userName = req.body.userName;
  console.log('POST existsUserName '+userName);
  User.countDocuments({ 'userName' : userName }, (err, count) => {
    if (err) {
      return res.status(500).send({message: `Error: ${err}`});
    }
    if (count == 0){
      return res.status(200).send();
    } else {
      generateNewUsernameAvailable(userName,1)
      .then(function(results){
        return res.status(400).send({message: results});
      })
      .catch(function(err){
        return res.status(500).send({message: `Error: ${err}`});
      });
    }
  })
}

Generate new username available, always getting Undefined

1 Answers1