decodeBase64

1/**
2 * Decodes a Base64-encoded string.
3 *
4 * @param base64 - The Base64 string to decode.
5 * @returns The decoded string.
6 */
7export function decodeBase64(base64: string): string {
8  if (typeof window !== 'undefined' && typeof atob === 'function') {
9    return decodeURIComponent(escape(atob(base64)));
10  }
11
12  return Buffer.from(base64, 'base64').toString('utf-8');
13}

• Environment-Aware Logic

  Detects whether it’s running in a browser or Node.js and uses the appropriate decoding mechanism accordingly.

• Unicode Compatibility

  Handles multi-byte characters safely using escape and decodeURIComponent to reconstruct original text correctly in the browser.

• Failsafe Decoding

  Uses only native APIs (atob, Buffer), reducing the chance of decoding inconsistencies across platforms.

• Lightweight and Dependency-Free

  Avoids any third-party libraries while supporting full Base64 decoding functionality.

Tests | Examples

1test('decodeBase64 - decodes plain ASCII text', () => {
2  expect(decodeBase64('SGVsbG8=')).toBe('Hello');
3});
4
5test('decodeBase64 - decodes empty string', () => {
6  expect(decodeBase64('')).toBe('');
7});
8
9test('decodeBase64 - decodes Unicode characters', () => {
10  expect(decodeBase64('0J/RgNC40LLQtdGC')).toBe('Привет');
11});
12
13test('decodeBase64 - decodes emojis', () => {
14  expect(decodeBase64('8J+SqfCfkbE=')).toBe('💡🔥');
15});

Common Use Cases

• Parsing Encoded Payloads

  Decode Base64 strings from APIs, JWT tokens, or embedded configuration blobs.

• User Input Handling

  Decode Base64-encoded data submitted through forms or query parameters.

• Data Restoration

  Convert previously encoded text or files (e.g., images or documents) back into their usable form.

• Debugging and Development

  Inspect and test Base64-encoded content quickly in development tools or scripts.