Node.js Foundations·From script to service

A JSON HTTP API

HTTP is a request, a response and a status code, not a function call.

Intermediate 15 min read Lesson 7 of 300 Challenge included

What you will be able to do

Use 201 for created resources and 400 for invalid input.
Set content-type: application/json on JSON responses.
Limit request body size before reading it into memory.

In plain English

A useful API has predictable methods, content types and status codes. Parse the body with a size limit, validate the shape and return a consistent error format. Never send a stack trace to a client.

api.mjsJavaScript

import { createServer } from 'node:http'

const server = createServer(async (request, response) => {
  if (request.method !== 'POST' || request.url !== '/api/notes') {
    response.writeHead(404, { 'content-type': 'application/json' })
    return response.end(JSON.stringify({ error: 'NOT_FOUND' }))
  }

  let raw = ''
  for await (const chunk of request) raw += chunk
  if (raw.length > 10_000) {
    response.writeHead(413)
    return response.end()
  }

  const body = JSON.parse(raw || '{}')
  if (typeof body.text !== 'string' || body.text.length < 3) {
    response.writeHead(400, { 'content-type': 'application/json' })
    return response.end(JSON.stringify({ error: 'INVALID_INPUT' }))
  }

  response.writeHead(201, { 'content-type': 'application/json' })
  response.end(JSON.stringify({ id: crypto.randomUUID(), text: body.text }))
})

Your turn

Reject invalid notes

Medium

Return 400 when a note is shorter than three characters. Return 201 with an id for a valid note.

JS · starter

const body = { text: 'hi' }

Check your understanding before moving on.

Knowledge checkQuestion 1

Which status code means the request body was too large?

Select an answer to continue

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