URLエンコーディング リファレンス

// Encode a single query param value (most common)
encodeURIComponent('hello world!')   // → 'hello%20world!'
encodeURIComponent('price=100&qty=2') // → 'price%3D100%26qty%3D2'

// Build a URL with params safely
const params = new URLSearchParams({ q: 'hello world', page: '2' });
const url = 'https://example.com/search?' + params.toString();
// → https://example.com/search?q=hello+world&page=2

// Decode percent-encoded string
decodeURIComponent('hello%20world')  // → 'hello world'

// Python
import urllib.parse
urllib.parse.quote('hello world')             # → 'hello%20world'
urllib.parse.quote_plus('hello world')        # → 'hello+world'
urllib.parse.urlencode({'q': 'hello world'})  # → 'q=hello+world'