Base64 Encode & Decode

// Browser - Encode to Base64
const text = 'Hello World';
const encoded = btoa(text);
console.log(encoded); // 'SGVsbG8gV29ybGQ='

// Browser - Decode from Base64
const decoded = atob('SGVsbG8gV29ybGQ=');
console.log(decoded); // 'Hello World'

// Handle Unicode characters (btoa doesn't support Unicode)
function encodeUnicode(str) {
  return btoa(encodeURIComponent(str).replace(/%([0-9A-F]{2})/g, (match, p1) => {
    return String.fromCharCode(parseInt(p1, 16));
  }));
}

function decodeUnicode(str) {
  return decodeURIComponent(Array.prototype.map.call(atob(str), c => {
    return '%' + ('00' + c.charCodeAt(0).toString(16)).slice(-2);
  }).join(''));
}

// Modern approach with TextEncoder/TextDecoder
function encodeBase64(str) {
  const bytes = new TextEncoder().encode(str);
  const binString = String.fromCodePoint(...bytes);
  return btoa(binString);
}

function decodeBase64(str) {
  const binString = atob(str);
  const bytes = Uint8Array.from(binString, (m) => m.codePointAt(0));
  return new TextDecoder().decode(bytes);
}

// File to Base64 (data URL)
function fileToBase64(file) {
  return new Promise((resolve, reject) => {
    const reader = new FileReader();
    reader.onload = () => resolve(reader.result);
    reader.onerror = reject;
    reader.readAsDataURL(file);
  });
}

// Usage
const file = document.querySelector('input[type="file"]').files[0];
const dataUrl = await fileToBase64(file);
// Result: data:image/png;base64,iVBORw0KGgoAAAANSUhEUgA...

import base64

# Encode to Base64
text = "Hello World"
encoded = base64.b64encode(text.encode('utf-8'))
print(encoded.decode('utf-8'))  # b'SGVsbG8gV29ybGQ='

# Decode from Base64
decoded = base64.b64decode(b'SGVsbG8gV29ybGQ=')
print(decoded.decode('utf-8'))  # 'Hello World'

# URL-safe Base64 (uses - and _ instead of + and /)
encoded_url_safe = base64.urlsafe_b64encode(text.encode('utf-8'))
decoded_url_safe = base64.urlsafe_b64decode(encoded_url_safe)

# File to Base64
with open('image.png', 'rb') as f:
    encoded_file = base64.b64encode(f.read())
    print(f"data:image/png;base64,{encoded_file.decode('utf-8')}")