Project: Full MERN Back-End

The brief

Build the complete back-end for an app of your choice (tasks, blog, products). This is the “EN-M” of MERN, ready for a React front-end.

Requirements

• Express server with express.json() and cors().
• MongoDB connection via Mongoose, using a .env connection string.
• A schema/model with validation.
• Full CRUD routes (list, get one, create, update, delete) in a Router.
• Proper status codes, a 404 handler and a central error handler.
• All async routes wrapped in try/catch.

Suggested structure

server/
  models/      Task.js          (schema + model)
  routes/      tasks.js         (the CRUD router)
  server.js    (connect db, middleware, mount routes)
  .env         (MONGO_URI, PORT)

Each part has one job. models/Task.js holds the Mongoose schema and model (the shape of your data). routes/tasks.js holds the CRUD router (the URLs clients call). server.js is the entry point that connects to the database, sets up middleware like express.json() and cors(), and mounts the router. (CORS stands for *Cross-Origin Resource Sharing* — a browser rule about which web addresses may call your API; the cors() middleware switches on permission so your React app, running on a different address, is allowed to talk to this server.) .env keeps secrets like MONGO_URI and PORT out of your code. Splitting files this way keeps the project tidy as it grows.

A sensible order to build it in:

1. Set up .env with your MONGO_URI and PORT, and add .env to .gitignore.
2. In server.js, create the Express app, add express.json() and cors(), and connect Mongoose.
3. Write the schema and model in models/Task.js (with validation rules).
4. Build the CRUD routes in routes/tasks.js, each async and wrapped in try/catch.
5. Mount the router in server.js and add a 404 handler and a central error handler.
6. Start the server, test every endpoint, then restart and confirm the data is still there.