How to Create REST API in Node.js with Express

To create a REST API in Node.js, use the Express framework to handle HTTP requests and define routes for different API endpoints. Set up routes with methods like GET, POST, PUT, and DELETE to manage data and send JSON responses.

Syntax

Here is the basic syntax to create a REST API route in Node.js using Express:

• const express = require('express'): Import Express library.
• const app = express(): Create an Express app instance.
• app.use(express.json()): Middleware to parse JSON request bodies.
• app.METHOD(PATH, HANDLER): Define a route where METHOD is HTTP method like GET or POST, PATH is the URL path, and HANDLER is a function to handle requests.
• res.json(DATA): Send JSON response to client.
• app.listen(PORT): Start server on given port.

javascript

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

app.use(express.json())

app.get('/api/example', (req, res) => {
  res.json({ message: 'Hello from API' })
})

app.listen(3000, () => {
  console.log('Server running on port 3000')
})

Output

Server running on port 3000

Example

This example shows a simple REST API with Express that handles GET and POST requests to manage a list of items in memory.

javascript

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

app.use(express.json())

let items = []

// Get all items
app.get('/api/items', (req, res) => {
  res.json(items)
})

// Add a new item
app.post('/api/items', (req, res) => {
  const newItem = req.body
  items.push(newItem)
  res.status(201).json(newItem)
})

app.listen(3000, () => {
  console.log('API server running on port 3000')
})

Output

API server running on port 3000

Common Pitfalls

Common mistakes when creating REST APIs in Node.js include:

• Not using express.json() middleware, so JSON request bodies are undefined.
• Forgetting to send a response, causing the request to hang.
• Using wrong HTTP methods or paths that don't match client requests.
• Not handling errors or invalid input properly.

javascript

/* Wrong: Missing JSON middleware, so req.body is undefined */
const express = require('express')
const app = express()

app.post('/api/data', (req, res) => {
  // req.body will be undefined
  res.json(req.body)
})

app.listen(3000)

/* Right: Add express.json() middleware */
app.use(express.json())

Quick Reference

Here is a quick reference for creating REST API routes in Express:

HTTP Method	Purpose	Example Route
GET	Retrieve data	app.get('/api/items', handler)
POST	Create new data	app.post('/api/items', handler)
PUT	Update existing data	app.put('/api/items/:id', handler)
DELETE	Delete data	app.delete('/api/items/:id', handler)

Key Takeaways

Use Express framework with express.json() middleware to create REST APIs in Node.js.

Define routes with app.get, app.post, app.put, and app.delete for different API actions.

Always send a response to avoid hanging requests.

Test your API endpoints with tools like Postman or curl.

Handle errors and invalid input gracefully in your API.