Unable to store query result inside a variable

All we need is an easy explanation of the problem, so here it is.

I am trying to query user by email and save the result inside a variable. I tried using await and async, callback and promise but none of them actually work.

const checkEmailUsed = (email) => {
  let sql = "SELECT * FROM users_signup WHERE user_email = ? LIMIT 1";
  return new Promise((resolve, reject) => {
    conn.query(sql, email, (err, res) => {
      if (err) {
        reject(err);
        return;
      }
      resolve(res[0]);
    });
    conn.end();
  });
};

var user = [];
checkEmailUsed("[email protected]")
  .then((res) => user.push(res))
  .catch((err) => console.log(err));

console.log(user); // Still []

How to solve :

I know you bored from this bug, So we are here to help you! Take a deep breath and look at the explanation of your problem. We have many solutions to this problem, But we recommend you to use the first method because it is tested & true method that will 100% work for you.

Method 1

The console.log is executed before the promise is fulfilled. This should work:

const checkEmailUsed = (email) => {
  let sql = "SELECT * FROM users_signup WHERE user_email = ? LIMIT 1";
  return new Promise((resolve, reject) => {
    conn.query(sql, email, (err, res) => {
      if (err) {
        reject(err);
        return;
      }
      resolve(res[0]);
    });
    conn.end();
  });
};

var user = [];
checkEmailUsed("[email protected]")
  .then((res) => user.push(res))
  .then(() => console.log(user))
  .catch((err) => console.log(err));

Note: Use and implement method 1 because this method fully tested our system.
Thank you 🙂

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