REST API with Express

What you'll build

Your first backend server with Node.js and Express. You'll create a complete REST API with endpoints to list, create, update, and delete tasks (CRUD). You'll learn how HTTP requests work (GET, POST, PUT, DELETE) and how the frontend communicates with the backend. By the end, you'll have a server running on your computer that responds to requests like a real API.

Step 1: Ask an AI for the code

I need a REST API with Express and Node.js that:
- Has CRUD endpoints for tasks (todos)
- Uses JSON for requests and responses
- Saves in memory (array)
- Has CORS enabled
- Port 3001

Give me the complete code.

Step 2: Create the project

mkdir todo-api
cd todo-api
npm init -y
npm install express cors

Paste the code the AI gave you in server.js

Step 3: Run it

node server.js

Step 4: Test with curl

# List all
curl http://localhost:3001/todos

# Create one
curl -X POST http://localhost:3001/todos \
  -H "Content-Type: application/json" \
  -d '{"text": "My first task"}'

# Update
curl -X PUT http://localhost:3001/todos/1 \
  -H "Content-Type: application/json" \
  -d '{"completed": true}'

# Delete
curl -X DELETE http://localhost:3001/todos/1

Typical code

const express = require('express')
const cors = require('cors')
const app = express()

app.use(cors())
app.use(express.json())

let todos = []
let nextId = 1

app.get('/todos', (req, res) => {
  res.json(todos)
})

app.post('/todos', (req, res) => {
  const todo = { id: nextId++, ...req.body, completed: false }
  todos.push(todo)
  res.status(201).json(todo)
})

app.listen(3001, () => console.log('API on port 3001'))

HTTP Methods

If something failed

Next step

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