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Summary - HTTP server

Combine createServer, routing and JSON to write an API.

Summary - HTTP server

In this group you learned the core tools of an HTTP server: setting up a server with createServer, handling request and response with req and res, routing with req.url, sending JSON responses with JSON.stringify and parsing query strings with new URL.

Now you will combine them into a small API. The API will return a JSON response to the /api path and a different JSON to other paths. This mini task shows how routing and JSON combine in a real API.

API design

The API skeleton: a createServer handler, routing with req.url and JSON response with JSON.stringify. The /api path gets a known JSON; other paths get a different JSON.

Flow: const server = http.createServer((req, res) => { res.setHeader("Content-Type", "application/json"); if (req.url === "/api") { res.end(JSON.stringify({ status: "ok" })); } else { res.end(JSON.stringify({ status: "none" })); } });. A /api request gets {"status":"ok"}; another path gets {"status":"none"}. The content type is set to application/json, so the client parses the response safely.

Practice Write an API

Import the http module. Create a server with createServer. Inside the handler call res.setHeader("Content-Type", "application/json"). If req.url === "/api" call res.end(JSON.stringify({ status: "ok" })), otherwise res.end(JSON.stringify({ status: "none" })). The ready-made code below sends a request to /api.

Starter code

index.js
// Import the http module and create a server
// write here

server.listen(3000, () => {
  http.get("http://localhost:3000/api", (res) => {
    let body = "";
    res.on("data", (c) => body += c);
    res.on("end", () => { console.log("Reply: " + body); server.close(); });
  });
});

Sample solution

index.js
const http = require("http");
const server = http.createServer((req, res) => {
  res.setHeader("Content-Type", "application/json");
  if (req.url === "/api") { res.end(JSON.stringify({ status: "ok" })); }
  else { res.end(JSON.stringify({ status: "none" })); }
});

server.listen(3000, () => {
  http.get("http://localhost:3000/api", (res) => {
    let body = "";
    res.on("data", (c) => body += c);
    res.on("end", () => { console.log("Reply: " + body); server.close(); });
  });
});

Expected output

Yanıt: {"durum":"ok"}

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 What pieces does the API combine?

index.js
if (req.url === "/api") { res.end(JSON.stringify(...)); }
  • Only createServer
  • createServer, routing ve JSON Correct answer
  • Only require
  • Only console.log

Explanation: createServer + routing (req.url) + JSON (JSON.stringify) combine.

2 Match each tool to its role

Term Meaning
createServer Creates the server
req.url Does routing
JSON.stringify Produces JSON response
setHeader Sets content type

All lessons in Intermediate

1 Events

  1. EventEmitter
  2. on and emit
  3. once
  4. removeListener
  5. error event
  6. Summary - Events

2 Streams

  1. What are streams?
  2. Readable stream
  3. Writable stream
  4. pipe
  5. Transform stream
  6. Summary - Streams

3 HTTP server

  1. http.createServer
  2. Request and response
  3. Routing
  4. JSON response
  5. Query string
  6. Summary - HTTP server

4 Project: Helper library

  1. Module design
  2. String helpers
  3. Number helpers
  4. Date helpers
  5. Putting it together

5 Express basics

  1. What is Express?
  2. express()
  3. app.get
  4. app.post
  5. app.listen
  6. Summary - Express basics

6 Middleware

  1. What is middleware?
  2. app.use
  3. Router middleware
  4. Error middleware
  5. Body parser
  6. Summary - Middleware

7 Routing

  1. Route parameters
  2. Query parameters
  3. express.Router
  4. Route groups
  5. Method chaining
  6. Summary - Routing

8 Project: Quiz app

  1. Quiz model
  2. Adding questions
  3. Running the quiz
  4. Score calculation
  5. Putting it together

9 Async patterns

  1. Async iteration
  2. Async generators
  3. Concurrency limit
  4. Retry pattern
  5. Debounce and throttle
  6. Summary - Async patterns

10 Buffer and binary

  1. What is Buffer?
  2. Buffer.from
  3. Buffer.concat
  4. toString and encoding
  5. Buffer slice
  6. Summary - Buffer

11 Process and CLI

  1. process.argv
  2. process.env
  3. process.exit
  4. process.stdin/stdout
  5. Child process
  6. Summary - Process

12 Project: Library API

  1. Model design
  2. Express app
  3. CRUD routes
  4. Middleware
  5. Putting it together

13 npm and packages

  1. npm install
  2. package.json scripts
  3. devDependencies
  4. Semver
  5. npm publish
  6. Summary - npm

14 Error handling

  1. The Error class
  2. try/catch
  3. Custom errors
  4. Error middleware
  5. Unhandled rejection
  6. Summary - Error handling

15 Testing basics

  1. node:test
  2. assert
  3. describe and it
  4. Before and after
  5. Mock
  6. Summary - Testing basics

16 Debugging

  1. node inspect
  2. Chrome DevTools
  3. console methods
  4. util.inspect
  5. Source maps
  6. Summary - Debugging

17 Date and time

  1. The Date object
  2. Date methods
  3. Intl.DateTimeFormat
  4. performance.now
  5. setTimeout and setInterval
  6. Summary - Date and time

18 Crypto

  1. crypto module
  2. createHash
  3. randomBytes
  4. HMAC
  5. AES
  6. Summary - Crypto

19 URL and query string

  1. URL object
  2. URLSearchParams
  3. URL properties
  4. URL.resolve
  5. querystring
  6. Summary - URL and query string

20 Intermediate final

  1. Project design
  2. Express API
  3. fs persistence
  4. Middleware
  5. Putting it together