Base64 encoder / decoder with unicode support

base64.js

// See https://github.com/gera2ld/js-lib

base64.legacy.js

const CHUNK_SIZE = 8192;

function bytes2string(bytes) {
  const chunks = [];
  for (let i = 0; i < bytes.length; i += CHUNK_SIZE) {
    chunks.push(String.fromCharCode(...bytes.slice(i, i + CHUNK_SIZE)));
  }
  return chunks.join('');
}

function utf8decode(binary) {
  const bytes = [];
  let i = 0;
  let c1 = 0;
  let c2 = 0;
  let c3 = 0;
  while (i < binary.length) {
    c1 = binary.charCodeAt(i);
    if (c1 < 128) {
      bytes.push(c1);
      i += 1;
    } else if (c1 > 191 && c1 < 224) {
      c2 = binary.charCodeAt(i + 1);
      // eslint-disable-next-line no-bitwise
      bytes.push(((c1 & 31) << 6) | (c2 & 63));
      i += 2;
    } else {
      c2 = binary.charCodeAt(i + 1);
      c3 = binary.charCodeAt(i + 2);
      // eslint-disable-next-line no-bitwise
      bytes.push(((c1 & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63));
      i += 3;
    }
  }
  return bytes2string(bytes);
}

/* eslint-disable no-bitwise */
function utf8encode(string) {
  const bytes = [];
  for (let i = 0; i < string.length; i += 1) {
    const code = string.charCodeAt(i);
    if (code < 128) {
      bytes.push(code);
    } else if (code < 2048) {
      bytes.push(
        (code >> 6) | 192,
        (code & 63) | 128,
      );
    } else {
      bytes.push(
        (code >> 12) | 224,
        ((code >> 6) & 63) | 128,
        (code & 63) | 128,
      );
    }
  }
  return bytes2string(bytes);
}

function base64decode(base64) {
  return utf8decode(atob(base64));
}

function base64encode(text) {
  return btoa(utf8encode(text));
}

base64.node.js

function base64encode(text) {
  return Buffer.from(text).toString('base64');
}

function base64decode(base64) {
  return Buffer.from(base64, 'base64').toString();
}