Get user id from jsonwebtoken in node with passport - node.js

Question

I use passport jwt strategy and here is my code snippet:
'use strict';
const config = require('../config');
const User = require('../models/user.model');
const passportJWT = require('passport-jwt');
const ExtractJwt = passportJWT.ExtractJwt;
const JwtStrategy = passportJWT.Strategy;
const jwtOptions = {
secretOrKey: config.secret,
jwtFromRequest: ExtractJwt.fromAuthHeaderAsBearerToken()
};
const jwtStrategy = new JwtStrategy(jwtOptions, (jwtPayload, done) => {
console.log(jwtPayload);
User.findById(jwtPayload.sub, (err, user) => {
if (err) return done(err, null);
if (user) {
return done(null, user)
} else {
return done(null, false)
}
})
});
exports.jwtOptions = jwtOptions;
exports.jwt = jwtStrategy;
here I'm setting the strategy and everything works correctly. Now I want to create endpoint to add article with UserId retrieved from the token (article has userId String in its schema).
How am I suppose to get userId from the token?
In new JwtStrategy it's already happening because I have payload which allow me to findById and therefore authenticate the call but should I somehow reuse this file or create new named for example getUserId?

Answer 1

The JWT claim that identifies the user presenting the JWT is sub. If understand your code correctly, jwtPayload.sub contains this claim.
If the value of the sub claim contains what you call the user ID, you are done.
If you want to find the user based on a different value, maybe one derived from the sub, you will have to tell us how this different value is related to the claims contained in the JWT.

Answer 2

While signing the JWT (creating the new token), if you would add the user info in the jwt payload something as below:
..
....
const payload = {
userId: user.id,
email: user.email
};
// CREATE A JWT TOKEN
jwt.sign(payload, secretForJWT, { expiresIn: expirationTimeForJWT },
(err, token) => {
....
..
Then you should be able to retrieve the userId field from the decrypted token as below:
const jwtStrategy = new JwtStrategy(jwtOptions, (jwtPayload, done) => {
console.log(jwtPayload);
const userId = jwtPayload.userId; // YOU SHOULD GET THE USER ID FROM THE PAYLOAD
User.findById(jwtPayload.sub, (err, user) => {
if (err) return done(err, null);
if (user) {
return done(null, user)
} else {
return done(null, false)
}
})
});
exports.jwtOptions = jwtOptions;
exports.jwt = jwtStrategy;

Answer 3

This is my way, hope it's helpful:
const jwt = require('jsonwebtoken');
...
const jwt_payload = jwt.decode(yourJwtInString);
const id = jwt_payload._id;
...