CODEWITHSUNDEEP
javascriptmysqlnode.jsexpresstypeerror
Proto
Proto

Reputation: 5

Cannot read property 'length' of undefined when trying to read the results of a MYSQL query

I've been stuck on this issue for a while and I could just be stupid, but I'm hoping it's not that bad. I've been tasked to create a simple system using NodeJS + Express + MYSQL. Where a user can login and out, while checking for already existing username/email

So the code that gives me the error I have currently (it has gone through many iterations and implementations)

var userExists;
var emailExists;

var userCheck = 'SELECT * FROM users WHERE uname =' + req.body.email;

connection.query(userCheck, function (error, results) {
    if (error) {
        userExists = true;
        res.json({
            status: false,
            message: 'there are some error with query'
        })}
        if (results.length > 0) {
            userExists = true;
            res.json({
                status: false,
                message: 'Username already exists'
            });
        } else {

            userExists = false;
        }
});

I get an issue of:

'TypeError: Cannot read property 'length' of undefined'

My head has been through a lot in the past 10 hours with this code but I'm hoping it's not too much of a rookie mistake! Any help will be appreciated!

Upvotes: 0

Views: 1273

Answers (1)

Snow
Snow

Reputation: 4097

Your current code will try to check the .length of results regardless of whether there's an error. If there's an error, results may be undefined, so proceeding to check results.length will throw. Consider returning at the bottom of the if (error) block:

connection.query(userCheck, function (error, results) {
  if (error) {
    userExists = true;
    res.json({
      status: false,
      message: 'there are some error with query'
    });
    return;
  }
  if (results.length > 0) {
    userExists = true;
    res.json({
      status: false,
      message: 'Username already exists'
    });
  } else {
    userExists = false;
  }
});

Upvotes: 1

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