base64.js

"use strict";

function toBinary(string) {
  const codeUnits = new Uint16Array(string.length);
  for (let i = 0; i < codeUnits.length; i++) {
    codeUnits[i] = string.charCodeAt(i);
  }
  return String.fromCharCode(...new Uint8Array(codeUnits.buffer));
}

function fromBinary(binary) {
  const bytes = new Uint8Array(binary.length);
  for (let i = 0; i < bytes.length; i++) {
    bytes[i] = binary.charCodeAt(i);
  }
  return String.fromCharCode(...new Uint16Array(bytes.buffer));
}

const myString = "☸☹☺☻☼☾☿";
const converted = toBinary(myString);
const encoded = btoa(converted);
console.log(encoded);

const decoded = atob(encoded);
const original = fromBinary(decoded);
console.log(original);