CODEWITHSUNDEEP
javascriptnode.jsexpressmongoosejwt
user13900804
user13900804

Reputation: 31

How to print out jwt token

I am trying to generate a jwt token and print it out by calling res.json() after the user has been authenticated, the problem is that I get the following error:

Cannot set headers after they are sent to the client

I tried solving the issue by using async and await but it still gives me the error. How can I res.json my token successfully?

Here is my node.js server:

const express = require('express');
const app = express();
const bodyParser = require('body-parser');
const cors = require('cors');
const mongoose = require('mongoose');
require('dotenv').config();
const BASE_URL = process.env.BASE_URL;
const PORT = process.env.PORT || 1337;
const jwt = require('jsonwebtoken');
let Post = require('./models/post.model.js');

app.use(cors());
app.use("/assets", express.static(__dirname + "/assets"));
app.use(bodyParser.urlencoded({ extended: true }));

mongoose.connect(BASE_URL, { useNewUrlParser: true, useUnifiedTopology: true })

const connection = mongoose.connection;

connection.once('open', function () {
    console.log('Connection to MongoDB established succesfully!');
});

app.set('view-engine', 'ejs');

app.get('/', (req, res) => {
    res.render('index.ejs');
});

app.post('/', (req, res) => {
    let username = req.body.username;
    let password = req.body.password;

    if (username !== process.env.USER_NAME && password !== process.env.USER_PASSWORD) {
        res.json('Invalid credentials');

    } else {
        const token = jwt.sign({
            username: username,
            password: password
        }, process.env.SECRET_KEY, {
            expiresIn: '1h'
        });

        res.redirect('/dashboard');
        res.json(token);
    }
});

app.get('/dashboard', (req, res) => {
    res.render('dashboard.ejs');
});

app.get('/dashboard/createPost', (req, res) => {
    res.render('post.ejs');
});

app.post('/dashboard/createPost', async (req, res) => {
    let collection = connection.collection(process.env.POSTS_WITH_TAGS);
    res.setHeader('Content-Type', 'application/json');
    let post = new Post(req.body);
    collection.insertOne(post)
        .then(post => {
            res.redirect('/dashboard')
        })
        .catch(err => {
            res.status(400).send(err);
        });
});

app.listen(PORT);

Upvotes: 0

Views: 1402

Answers (1)

Owl
Owl

Reputation: 6853

You are calling res.redirect('/dashboard'); before the res.json(token);, you can't send a response twice that's why it's giving you the Cannot set headers after they are sent error.

What you can do instead is sending the token as a query via the redirect like this:

res.redirect(`/dashboard?token=${token}`);

Then you can get the token value from the front-end app by checking the query value.

Although this is not a very safe method

Upvotes: 1

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