I'm learning node and I'm migrating my current API from python. I'm trying to create a jwt token to authenticate in a third party API, however my function returns undefined. The jwt method I'm using to sign the token is async, so I guess my function doesn't wait until jwt returns the token.

This is my function to sign and create the jwt token:

function token() {
  const payload = {
    iat: Math.floor(new Date() / 1000),
    exp: Math.floor(new Date() / 1000) + 30,
    sub: "api_key_jwt",
    iss: "external",
    jti: crypto.randomBytes(6).toString("hex")
  };
  return jwt.sign(payload, privatekey, { algorithm: "RS256" }, function(
    err,
    token2
  ) {
    return token2;
  });
}

So, when I call it:

exports.genToken = function() {
  const header = {
    "x-api-key": api
  };
  const data = {
    kid: api,
    jwt_token: token()
  };

  async function authorization(req, res) {
    try {
      const auth = await rp({
        url: authurl,
        method: "POST",
        headers: header,
        body: data
      });
      res.send(auth.body);
    } catch (error) {
      res.send(404).send();
    }
  }

  return {
    "x-api-key": api,
    Authorization: "Bearer " + authorization()
  };
};

jwt_token returns undefined. What am I doing wrong, and how can I fix it?

Thanks in advance guys!

Edit: console.log(token2) returns the signed token. So the problem is returning the token from the token() function

I'm learning node and I'm migrating my current API from python. I'm trying to create a jwt token to authenticate in a third party API, however my function returns undefined. The jwt method I'm using to sign the token is async, so I guess my function doesn't wait until jwt returns the token.

This is my function to sign and create the jwt token:

function token() {
  const payload = {
    iat: Math.floor(new Date() / 1000),
    exp: Math.floor(new Date() / 1000) + 30,
    sub: "api_key_jwt",
    iss: "external",
    jti: crypto.randomBytes(6).toString("hex")
  };
  return jwt.sign(payload, privatekey, { algorithm: "RS256" }, function(
    err,
    token2
  ) {
    return token2;
  });
}

So, when I call it:

exports.genToken = function() {
  const header = {
    "x-api-key": api
  };
  const data = {
    kid: api,
    jwt_token: token()
  };

  async function authorization(req, res) {
    try {
      const auth = await rp({
        url: authurl,
        method: "POST",
        headers: header,
        body: data
      });
      res.send(auth.body);
    } catch (error) {
      res.send(404).send();
    }
  }

  return {
    "x-api-key": api,
    Authorization: "Bearer " + authorization()
  };
};

jwt_token returns undefined. What am I doing wrong, and how can I fix it?

Thanks in advance guys!

Edit: console.log(token2) returns the signed token. So the problem is returning the token from the token() function

• javascript
• node.js
• express
• jwt

• Can you console.log the err variable in the callback function and post it's results? Does it contain an error? – George Koniaris Commented Apr 18, 2019 at 14:40
• Hi George, I edited the question. Actually the token is being signed by the jwt.sign, however it doesn't return to the token() function – Otavio Bonder Commented Apr 18, 2019 at 14:44

2 Answers 2

You're trying to return from a callback which doesn't work. Change your token function to return Promise then you can use the async/await like:

function token() {
  ...

  return new Promise((resolve, reject) => {
    jwt.sign(payload, privatekey, { algorithm: "RS256" }, function(err, token2) {
      if (err) reject(err);
      else resolve(token2)
    });
  })
}

// note async
exports.genToken = async function() {
  ...
  const data = {
    kid: api,
    jwt_token: await token()
  };
  ...
}

Here is the catch if you supply jwt.sign with the callback function it will work in async mode and going to return undefined so just omit the callback and it will work your function will look like

function token() {
  const payload = {
    iat: Math.floor(new Date() / 1000),
    exp: Math.floor(new Date() / 1000) + 30,
    sub: "api_key_jwt",
    iss: "external",
    jti: crypto.randomBytes(6).toString("hex")
  };
  return jwt.sign(payload, privatekey, { algorithm: "RS256" });
}