REST APIs

This lesson covers REST APIs. Let us learn this step by step — no rush, no jargon first.

What you will learn

• What rest apis means — in normal words, not textbook words
• How it works step by step
• Code you can run today on your laptop
• Where teams use this in real projects

Before you start

• Software: Node.js LTS from nodejs.org, VS Code, and a terminal
• Knowledge: Earlier lessons in this Node.js course
• Previous lesson: Enterprise MVC Architecture — Complete Guide

Explain it simply

REST is a style for HTTP APIs: use URLs for resources and HTTP methods for actions — GET to read, POST to create, etc.

Why developers use this

• Standard way mobile and web apps talk to servers
• Easy to test with curl or Postman
• Maps cleanly to CRUD

How it works (step by step)

1. Client sends HTTP method + URL + optional JSON body.
2. Server validates input — reject bad data with 400.
3. Business logic reads or writes the database.
4. Response is JSON with a clear message the frontend can show.

Code example — type this yourself

app.get('/api/tasks', (req, res) => res.json(tasks));
app.post('/api/tasks', (req, res) => {
  const task = { id: Date.now(), title: req.body.title };
  tasks.push(task);
  res.status(201).json(task);
});

Return JSON with res.json. Use 201 Created after POST. Keep a tasks array in memory for practice.

What each part does

• app.get('/api/tasks', (req, res) => res.json(tasks)); — Sends the response back to the client.
• app.post('/api/tasks', (req, res) => { — Defines what happens when a client hits this URL and HTTP method.
• const task = { id: Date.now(), title: req.body.title }; — Line 3: runs as written.
• tasks.push(task); — Line 4: runs as written.
• res.status(201).json(task); — Line 5: runs as written.
• }); — Line 6: runs as written.

Real life: where REST APIs shows up

A mobile app talks to a Node backend using REST APIs. The phone sends JSON; the server validates, saves to PostgreSQL, and returns clear success or error messages.

Try it yourself — hands-on

1. Add a tasks array
2. Test GET with browser or curl
3. POST JSON with curl -d '{"title":"Learn Node"}' -H "Content-Type: application/json"

Common mistakes (avoid these)

• Using GET to delete data — use DELETE method instead.

Interview note

Be ready to explain REST APIs with a real trade-off: what problem it solves and what you would not use it for.

Summary

• GET reads, POST creates
• Use proper status codes
• Send JSON with Content-Type application/json