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URL.resolve

Learn to resolve relative URLs with URL.resolve.

Resolving relative URLs

When a page has a relative link like "/sub", the browser turns it into a full address. This is called URL resolution. In Node.js you do it with new URL(relative, base).

Example: new URL("sub", "https://example.com/main") gives https://example.com/sub. new URL("../sibling", "https://example.com/a/b/c") gives https://example.com/a/sibling. base is the second parameter; the relative path is resolved against it. Older Node.js versions had a url.resolve(base, relative) function; it has been removed. In new code always use new URL(relative, base). This is useful for crawling relative links on a page or building endpoints from an API base.

Base and relative interaction

The result of resolution comes from the relative path replacing the last path component of the base. "./" means the same directory, "../" the parent, "/" the root.

Examples: new URL("./x", "https://example.com/a/b") → https://example.com/a/x; new URL("../x", "https://example.com/a/b") → https://example.com/x; new URL("/x", "https://example.com/a/b") → https://example.com/x. If the relative path contains a protocol like https://, the base is ignored; the absolute URL is used directly. This matches the <a href> logic in browsers. Resolving all links of a site from a single base keeps behavior consistent.

Practice Resolve a relative URL

Define const base = "https://example.com/ana/sayfa";. Resolve with const resolved = new URL("alt", base);. Print with console.log(resolved.href).

Starter code

index.js
// Define the base address
// write here

// Resolve the relative path
// write here

// Print the result
// write here

Sample solution

index.js
const base = "https://example.com/ana/sayfa";
const resolved = new URL("alt", base);
console.log(resolved.href);

Expected output

https://example.com/ana/alt

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 resolve a relative URL?

index.js
new URL("alt", "https://example.com/ana")
  • new URL(relative, base) Correct answer
  • url.resolve(base, rel)
  • url.parse(rel)
  • path.join(base, rel)

Explanation: new URL(relative, base) is the modern and recommended way.

2 Match each relative path to its meaning

Term Meaning
./x Same directory
../x Parent directory
/x Root directory
https://... Absolute (base ignored)

3 Complete the resolution call

Question 
const resolved = new URL(____, base);
Answer 
const resolved = new URL("alt", base);

Explanation: The relative path "alt" is resolved against the base.

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