method in express js get() - returns undefined

Question

I have this Node.js code that should, using Express.js http get, decode my jwt token from my http auth header.

When I write the code of decodeToken() inside of my express js get() method, everything works fine.

When I extract it to outside method (decodeToken() method) I get that undefined value from this method. Mind you, when this code was hard coded inside of the method get() it works.

Why is that, the async nature of Node.js? Does the method finish after the get() method was supposed to assign the token?

If I will use promises, will it solve that?

var jwtCheck = expressJwt({ secret: "some secret" }); app.use('/test', jwtCheck); app.get('/test', function (req, res) { var token = req.get('Authorization').split("Bearer ")[1]; var information = decodeToken(token) console.log("information: "+information); if (information!=null) { res.json(information); } else { res.json('Failed to authenticate token.'); } }); var decodeToken = function (token) { console.log(token); jwt.verify(token, secret, function (err, decoded) { if (err) { console.log('Failed to authenticate token.'); return null; } else { return (decoded); } }); } var getToken = function (req) { return req.get('Authorization').split("Bearer ")[1]; }

One thing I can see is that secret passed to jwt.verify is not defined anywhere — Mchl
– Mchl, Commented Nov 18, 2016 at 22:34

Ryan · Accepted Answer · 2016-11-18 22:55:55Z

jwt.verify is async because you pass a callback to it so anything that calls it needs to handle that. You could look at promises to clean up the logic a little bit but just using the code you have you could modify it like this:

var jwtCheck = expressJwt({ secret: "some secret" }); app.use('/test', jwtCheck); app.get('/test', function (req, res) { var token = req.get('Authorization').split("Bearer ")[1]; // pass callback to decodeToken that gets called after the token is verified decodeToken(token, function(information) { // this function won't execute until decodeToke calls it as `next()` console.log("information: "+information); if (information!=null) { res.json(information); } else { res.json('Failed to authenticate token.'); } }) }); // accept `next` callback var decodeToken = function (token, next) { console.log(token); jwt.verify(token, secret, function (err, decoded) { if (err) { console.log('Failed to authenticate token.'); return next(null); } else { return next(decoded); } }); } var getToken = function (req) { return req.get('Authorization').split("Bearer ")[1]; }

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