Node.js · Chapter 15 of 43

URL & Query Strings

The `url` module (and the global `URL` class) helps parse URLs into their parts: protocol, host, pathname, and query string parameters.

Query strings carry extra data in a URL after a `?`, like `?search=node&page=2`, and are commonly used for filtering or pagination.

Parsing URLs

The `URL` class parses a full URL string into properties like `.pathname`, `.searchParams`, and `.hostname`.

Reading query parameters

`url.searchParams.get('key')` retrieves a specific query parameter's value.

Example 1 (javascript)

const { URL } = require('url');
const myUrl = new URL('http://localhost:3000/search?term=node&page=2');
console.log(myUrl.pathname);
console.log(myUrl.searchParams.get('term'));

Output

/search
node

The URL is parsed into pathname and accessible query parameters.

Example 2 (javascript)

for (const [key, value] of myUrl.searchParams) {
  console.log(key, value);
}

Output

term node
page 2

searchParams is iterable, letting you loop over all query parameters.

Key points

The URL class parses full URLs into structured parts.
searchParams.get() reads a specific query parameter.
Query strings appear after a '?' in a URL.
searchParams is iterable for looping over all params.

💡 Note: In Express, query strings are automatically parsed into `req.query`.

URL & Query Strings

Parsing URLs

Reading query parameters

Key points

📝 Quick Quiz