URL-Safe Base64 encode/decode in TypeScript/JavaScript

base64codec.ts

/** Returns a Base64-encoded string is safe to embed in URLs. */
function base64UrlEncode(str: string) {
  return btoa(str).replace(/\+/g, '-').replace(/\//g, '_').replace(/=+$/, '');
}

/**
 * Deocdes a string of URL-safe, Base64-encoded data into bytes, and encodes
 * those bytes into a string using Latin-1 (ISO-8859-1).
 *
 * The input data is typically encoded with a `base64UrlEncode` method.
 * @param val The URL-safe, Base64-encoded input string.
 * @returns The decoded string.
 */
 function base64UrlDecode(base64str: string): string {
   return atob(base64str.replace(/-/g, '+').replace(/_/g, '/'));
 }