👀 Views: 86 💬 Answers: 1 📅 Created: 2025-07-08

node.js express jwt middleware authentication javascript

I'm sure I'm missing something obvious here, but I'm experimenting with I'm stuck on something that should probably be simple. I've been struggling with this for a few days now and could really use some help. I'm currently building an Express.js application using Node.js v14.17.0, and I'm working with a frustrating scenario with my JWT authentication middleware. I have a middleware function that checks for a valid JWT token in the authorization header, but I'm getting a `TypeError: want to read properties of undefined (reading 'split')` behavior when I try to access the token. Here's the middleware code: ```javascript const jwt = require('jsonwebtoken'); const authenticateToken = (req, res, next) => { const authHeader = req.headers['authorization']; const token = authHeader.split(' ')[1]; // This line throws the behavior if authHeader is undefined if (!token) return res.sendStatus(401); jwt.verify(token, process.env.ACCESS_TOKEN_SECRET, (err, user) => { if (err) return res.sendStatus(403); req.user = user; next(); }); }; ``` I've checked that I'm sending the `Authorization` header from the client, but it seems that in some cases, the `authHeader` is undefined. I tried logging the `authHeader` before the split operation, and indeed, it returns `undefined` on certain requests. This is confusing because I have other routes that work fine with the same middleware. I've implemented behavior handling and ensured that the client always sends the header in the format: `Bearer <token>`. I added a check for `authHeader` to return a 401 status if it's not present, but I’m still hitting this behavior intermittently. Can anyone guide to understand what might be causing this scenario? I'm using Express v4.17.1 and have also verified that my requests are properly formatted. Any thoughts or suggestions would be appreciated! For context: I'm using Javascript on Ubuntu. Is there a better approach? This is part of a larger CLI tool I'm building. What's the best practice here? I'm coming from a different tech stack and learning Javascript. Any advice would be much appreciated. This is happening in both development and production on macOS. Any advice would be much appreciated. I'm on Windows 10 using the latest version of Javascript. What am I doing wrong?