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How does a server know who you are on every request? Many beginners think the server remembers them after login. That's not true. HTTP is stateless. Every request arrives like a stranger, with no memo
How does a server remember that you are logged in? You log in once. Then you open ten more pages, and the app never asks for your password again. Many beginners think the server simply "remembers" the
Where do uploaded files go after Multer saves them? Many beginners think an uploaded file lives inside the request, or inside the database. That's not true. A file is just bytes written to a disk. You
Why can't Express read a file upload on its own? You build a form with a file input. You submit it. You log req.body. It is empty. Many beginners think Express is broken or that it express.json() shou
What does "REST API" actually mean? Many beginners think REST is a library or a framework you install. That's not true. REST is a set of rules for how a client and a server talk to each other over HTT
What happens to a request before it reaches your route? You send a request to /api/users. Your route handler sends back a response. Many beginners think the request goes straight from the browser to t
How does Express know which user you want, and how do you filter the results? You open /users/42 and get one user. You open /search?q=laptop&sort=price and get a filtered list. Both look like normal U
Why Does Everyone Use Express Instead of Plain Node.js? Many beginners think Express is some separate framework that replaces Node.js entirely - like choosing React instead of vanilla JavaScript. That
Why does Node.js need async code at all? Many beginners think Node.js is fast because it does many things at once. That's not true. Node.js runs your JavaScript on a single thread. It can only run one