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Summary - URL and query string

Combine URL, URLSearchParams and querystring to write a URL parser.

Summary - URL and query string

In this group you learned Node.js's URL tools: parsing with new URL(), query management with URLSearchParams, properties like pathname/hostname, relative resolution with new URL(relative, base), and the querystring module. Now we will combine them in a URL parser.

Structure: parse a URL with new URL(), turn its query into an object with querystring.parse, print hostname and query values on separate lines. This is the foundational step of a real web scraper or API client: you first parse the address, then take the query parameters. The output is deterministic because the address and query are fixed.

Practice Write a URL parser

Create a URL with const url = new URL("https://example.com:8080/path?q=merhaba&s=1");. Import with const querystring = require("node:querystring");. Parse the query with const parsed = querystring.parse(url.search.slice(1)); (skip the ? with slice(1)). Print with console.log(url.hostname), console.log(parsed.q) and console.log(parsed.s).

Starter code

index.js
// Create a URL
// write here

// Import the querystring module
// write here

// Parse the query (skip the ? mark)
// write here

// Print hostname, q and s values
// write here

Sample solution

index.js
const url = new URL("https://example.com:8080/path?q=merhaba&s=1");
const querystring = require("node:querystring");
const parsed = querystring.parse(url.search.slice(1));
console.log(url.hostname);
console.log(parsed.q);
console.log(parsed.s);

Expected output

example.com
merhaba
1

Questions and answers

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

1 What is the modern way to get a URL's query parameters?

index.js
url.searchParams.get("q")
  • Only regex
  • Only String.split("&")
  • URLSearchParams veya url.searchParams Correct answer
  • Only the querystring module

Explanation: URLSearchParams is the modern and recommended way.

2 Match each tool to its purpose

Term Meaning
new URL() Parses address
URLSearchParams Manages query
pathname Path component
querystring Legacy query module

3 Complete the URL construction

Question 
const url = new ____(adres);
Answer 
const url = new URL(adres);

Explanation: new URL parses the address.

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