Encode and decode base64 with javascript

base64.js

function encodeBase64(str) {
  return window.btoa(unescape(encodeURIComponent(str)));
}

function decodeBase64(str) {
  return decodeURIComponent(escape(window.atob(str)));
}

// Usage:
encodeBase64('✓ à la mode'); // "4pyTIMOgIGxhIG1vZGU="
decodeBase64('4pyTIMOgIGxhIG1vZGU='); // "✓ à la mode"