Node.js has access to OS level functionality, like networking tools. This allows us to build very capable servers. Mixed with the fact that Node.js is single threaded and runs an even loop for async tasks, Node.js is widely used for API's that need to respond fast and don't require heavy CPU intensive work.

The hard way

Node.js ships with the http module. This module is an abstraction around OS level networking tools. For Node.js, the http module would be considered "low level". Let's create a simple server.

import http from 'http'

const host = 'localhost'
const port = 8000

const server = http.createServer((req, res) => {
  if (req.method === 'POST') {
    let body = ''

    req.on('data', chunk => {
      body += chunk.toString()
    })

    req.on('end', () => {
      if (req.headers['content-type'] === 'application/json') {
        body = JSON.parse(body)
      }

      console.log(body)
      res.writeHead(201)
      res.end('ok')
    })
  } else {
    res.writeHead(200)
    res.end('hello from my server')
  }

})

server.listen(port, host, () => {
  console.log(`Server is running on http://${host}:${port}`)
})

Using the createServer method on the http module, we create a server. Before we start the server, we need to make sure it can handle incoming requests. That's the callback inside of createServer. Next is starting the server. To do that, we need a port and a host. Sites default to port 8080 or 8000 so it's not uncommon to use that when developing locally. The host is going to be your machine, which is localhost or 127.0.0.1.

Using the http module is fine for this small example, but for bulding real world APIs we should utilize the community and install some packages to help up with this task.

Express

There is an awesome packaged, express, that makes creating servers in Node.js a breeze. We're going to use it now.

npm install express body-parser morgan

express - a framework for building servers
body-parser - a middleware that parses incoming requests
morgan = a middleware for logging incoming requests

With everything installed, we'll create a simple API for a todo app using express.

import express from 'express'
import morgan from 'morgan'
import bp from 'body-parser'

const { urlencoded, json } = bp

const db = {
  todos: [],
}

const app = express()

app.use(urlencoded({ extended: true }))
app.use(json())
app.use(morgan('dev'))

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

app.post('/todo', (req, res) => {
  const newTodo = { complete: false, id: Date.now(), text: req.body.text }
  db.todos.push(newTodo)

  res.json({ data: newTodo })
})

app.listen(8000, () => {
  console.log('Server on http://localhost:8000')
})

Compared to the native http module, express feels like cheating.

Our todo API has two routes:

GET /todo - get all todos
POST /todo - create a new todo

Express has a healthy community with tons of plugins and middleware to help you build out API's. I have a course or two showing you how! Check those out to really learn how to get the best of Express.

Servers

The hard way

Express