JS async function returning undefined although calling it inside an asynchronous function

Question

I am using nodeJs Express and I have an async function which is used in another function.

here is my code:

/* get user info */
const getUserInfo = async (req) => {
    let userID = req.cookies.userId;
    if(!userID) return null;
    await connection.query('SELECT * FROM users WHERE id = ' + userID,
        function (err, rows, fields) {
            if (err) throw err
            // if user not found
            if (rows.length === 0) {
                return null;
            }
            // if user found
            else {
                return rows[0];
            }
        });
}

/* display dashboard page */
router.get("/", async function (req, res, next) {
    let userInfo = await getUserInfo(req);

    console.log(userInfo) // It's result is undefined


    if (userInfo) {
        res.render('dashboard/profile', {
            fullName: userInfo.fname + " " + userInfo.lname,
            email: userInfo.email,
            phone: userInfo.phone,
        });
    }
    else {
        res.render('authentication/register', {
            title: 'ثبت نام',
        });
    }

});

how to resolve this problem? I need userInfo retun me some data.

`connection.query(query, callback)` does not return a Promise - async/await is not syntax for using asynchronous callbacks - it's 100% only used for **Promises** — Bravo, May 01 '22 at 09:03

score 1 · Answer 1 · answered May 01 '22 at 09:05

await is only useful if the value on the right-hand side is a promise.

connection.query is taking a callback function, which implies it isn't returning a promise.

You need to either:

Find out how to make the API you are using return a promise (if that is possible)
Wrap the callback in a promise
Replace the API with one that supports promises natively

You also need getUserInfo to have a return statement of its own.

score 0 · Answer 2 · answered May 01 '22 at 09:38

You have to return some value from your getUserInfo function

If connection query doesn't support promise you should wrap it like this

/* get user info */
const getUserInfo = async(req) => {
  let userID = req.cookies.userId;
  if (!userID) return null;
  return new Promise((resolve, reject) => {
    connection.query('SELECT * FROM users WHERE id = ' + userID,
      function(err, rows, fields) {
        if (err) {
          reject(err)
          return;
        }
        // if user not found
        if (rows.length === 0) {
          resolve(null)
        }
        // if user found
        else {
          resolve(rows[0]);
        }
      });
  });
}

JS async function returning undefined although calling it inside an asynchronous function

2 Answers2