Folder Structure

Now we’re moving from Node.js core APIs into how apps are usually structured in the real world. Node itself doesn’t enforce folder structure, but when building web apps (esp. with Express), a clean layout makes your code scalable, testable, and maintainable.

Here’s the standard breakdown:

---

📂 Typical Node.js Project Structure

project-root/
│
├── src/                  # Main application source code
│   ├── routes/           # Route definitions (Express routers)
│   ├── controllers/      # Request handlers (business logic)
│   ├── models/           # Database models (e.g., Mongoose, Sequelize)
│   ├── middlewares/      # Express middleware (auth, logging, validation)
│   ├── utils/            # Helper functions (e.g., token generation)
│   ├── config/           # Config files (db, env vars)
│   └── app.js            # App bootstrap (Express app setup)
│
├── tests/                # Unit/integration tests
├── node_modules/         # Installed dependencies
├── package.json          # Project metadata, scripts, dependencies
├── .env                  # Environment variables (gitignored)
└── server.js             # Entry point (starts Express server)

---

🛠️ 1. src/routes/

Defines API endpoints, usually mapped to controllers.

Example: src/routes/userRoutes.js

const express = require("express");
const router = express.Router();
const userController = require("../controllers/userController");
 
router.get("/", userController.getAllUsers);
router.post("/", userController.createUser);
 
module.exports = router;

---

🛠️ 2. src/controllers/

Implements business logic.

Example: src/controllers/userController.js

const User = require("../models/User");
 
exports.getAllUsers = async (req, res) => {
  const users = await User.find();
  res.json(users);
};
 
exports.createUser = async (req, res) => {
  const user = new User(req.body);
  await user.save();
  res.status(201).json(user);
};

---

🛠️ 3. src/models/

Database layer (often with an ORM like Mongoose for MongoDB or Sequelize for SQL).

Example: src/models/User.js

const mongoose = require("mongoose");
 
const userSchema = new mongoose.Schema({
  name: String,
  email: { type: String, unique: true },
  password: String
});
 
module.exports = mongoose.model("User", userSchema);

---

🛠️ 4. src/middlewares/

Middleware functions → run before or after route handlers.

Example: src/middlewares/authMiddleware.js

module.exports = (req, res, next) => {
  const token = req.headers["authorization"];
  if (!token) return res.status(401).json({ error: "Unauthorized" });
 
  // validate token...
  next();
};

---

🛠️ 5. src/app.js

Sets up the Express app.

const express = require("express");
const userRoutes = require("./routes/userRoutes");
 
const app = express();
 
app.use(express.json());
app.use("/users", userRoutes);
 
module.exports = app;

---

🛠️ 6. server.js

Entry point that starts the server.

const app = require("./src/app");
 
const PORT = process.env.PORT || 3000;
 
app.listen(PORT, () => {
  console.log(`Server running on port ${PORT}`);
});

---

✅ In Short

• routes/ → define endpoints.

• controllers/ → handle request/response logic.

• models/ → interact with the database.

• middlewares/ → reusable request-processing functions.

• src/ → keeps app code separate from config and scripts.

---