Encodeur et décodeur Base64

// Encode string to Base64 (handles Unicode, safe for large strings)
function encodeBase64(str) {
  const bytes = new TextEncoder().encode(str);
  let binary = '';
  for (let i = 0; i < bytes.length; i++) {
    binary += String.fromCharCode(bytes[i]);
  }
  return btoa(binary);
}

// Decode Base64 back to string
function decodeBase64(b64) {
  const binary = atob(b64);
  const bytes = new Uint8Array(binary.length);
  for (let i = 0; i < binary.length; i++) {
    bytes[i] = binary.charCodeAt(i);
  }
  return new TextDecoder().decode(bytes);
}

const credentials = btoa('username:password');
fetch('/api/data', {
  headers: { 'Authorization': 'Basic ' + credentials }
});

import base64

# Encode string to Base64
encoded = base64.b64encode(b'Hello, World!').decode('utf-8')
print(encoded)  # SGVsbG8sIFdvcmxkIQ==

# Decode Base64 back to bytes
decoded = base64.b64decode(encoded)
print(decoded.decode('utf-8'))  # Hello, World!

# URL-safe variant
url_safe = base64.urlsafe_b64encode(b'data+here/now')
decoded2 = base64.urlsafe_b64decode(url_safe)

import base64

with open('image.png', 'rb') as f:
    b64_str = base64.b64encode(f.read()).decode('utf-8')

data_uri = f'data:image/png;base64,{b64_str}'

<!-- Inline PNG image -->
<img src="data:image/png;base64,iVBORw0KGgo..." alt="Logo">

<!-- Inline SVG as background -->
<style>
  .icon {
    background-image: url("data:image/svg+xml;base64,PHN2Zy4uLg==");
    width: 24px; height: 24px;
  }
</style>

<!-- Inline font face -->
<style>
  @font-face {
    font-family: 'MyFont';
    src: url('data:font/woff2;base64,d09GMgAB...') format('woff2');
  }
</style>

# HTTP header — base64(username:password)
Authorization: Basic dXNlcm5hbWU6cGFzc3dvcmQ=

# curl example
curl -H "Authorization: Basic $(echo -n 'user:pass' | base64)" \
     https://api.example.com/data

// JSON payload with Base64-encoded file
{
  "filename": "photo.jpg",
  "mime_type": "image/jpeg",
  "data": "/9j/4AAQSkZJRgAB..."
}

// JWT token structure (URL-safe Base64, no padding)
// header.payload.signature
// eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJ1c2VyIn0.abc123