atob.js/node-atob.js

"use strict";

const b64Alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/='

function atob(str) {
  for (const ch of str)
    if (!b64Alphabet.includes(ch))
      throw new Error(`Invalid character '${ch}' in base64 String`);
  return Buffer.from(str, 'base64').toString('binary');
}

module.exports = atob.atob = atob;