Built-In Middleware with Code Examples

Built-in middleware is already provided by Express. You don't need to create it — you just use it directly.


Common Built-In Middleware

express.static()

➤ Serves static files like CSS, JS, images.

➤ Example: Serves files from a folder (public).


express.urlencoded()

➤ Parses incoming form data (application/x-www-form-urlencoded).

➤ Helps you access form data via req.body.


Basic Code

import express from "express";
const app = express();


Form Data Undefined

app.post("/submit", (req, resp) => {
console.log("user login details are :", req.body); // undefined without middleware
resp.send("Submit Page");
});


Use built-in middleware before routes:

app.use(express.urlencoded({ extended: false }));

This allows Express to read data from the form (like email & password).


Use express.static()

To serve static CSS file:

  1. Create folder: public
  2. Add file: public/style.css
  3. In HTML:
<link rel="stylesheet" href="/style.css" />


In index.js:

app.use(express.static("public"));

Now Express will automatically serve CSS and other static files from public/.


Folder Structure:

project/
├── public/
│ └── style.css
├── view/
│ └── home.html
└── server.js