Base64.js

/**
 *  Base64 encode/decode
 *  Inspired by: https://github.com/davidchambers/Base64.js/blob/master/base64.js
 */
const chars =
  'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/='
export const Base64 = {
  btoa: (input) => {
    let str = input
    let output = ''

    for (
      let block = 0, charCode, i = 0, map = chars;
      str.charAt(i | 0) || ((map = '='), i % 1);
      output += map.charAt(63 & (block >> (8 - (i % 1) * 8)))
    ) {
      charCode = str.charCodeAt((i += 3 / 4))

      if (charCode > 0xff) {
        throw new Error(
          "'btoa' failed: The string to be encoded contains characters outside of the Latin1 range.",
        )
      }

      block = (block << 8) | charCode
    }

    return output
  },

  atob: (input) => {
    let str = input.replace(/=+$/, '')
    let output = ''

    if (str.length % 4 == 1) {
      throw new Error(
        "'atob' failed: The string to be decoded is not correctly encoded.",
      )
    }
    for (
      let bc = 0, bs = 0, buffer, i = 0;
      (buffer = str.charAt(i++));
      ~buffer && ((bs = bc % 4 ? bs * 64 + buffer : buffer), bc++ % 4)
        ? (output += String.fromCharCode(255 & (bs >> ((-2 * bc) & 6))))
        : 0
    ) {
      buffer = chars.indexOf(buffer)
    }

    return output
  },
}