​

function encode_utf8(str)

{

 return unescape( encodeURIComponent(str) );

}

​

function decode_utf8(str)

{

 return decodeURIComponent( escape(str) );

}

​

function encodeBase64(binary)

{

 var currBinaries;

 var iPlus5;

 var encoded;

 var res = "";

 for (i = 0; i < binary.length; i += 5)

 {

  iPlus5 = i + 5;

  currBinaries = binary.substring(i, iPlus5);

  currBinaries = currBinaries.replace(/\s/g, "");

  encoded = window.btoa( encode_utf8(currBinaries) )

  res += encoded;

 }

 return res;

}

​

function decodeBase64(encoded)

{

 var iPlus5;

 var currEncoded;

 var decoded;

 var res = "";

 for (i = 0; i < encoded.length; i += 5)

 {

  iPlus5 = i + 5;

  currEncoded = encoded.substring(i, iPlus5);

  currEncoded = currEncoded.replace(/\s/g, "");

  decoded = window.atob( decode_utf8(currEncoded) );

  res += decoded;

 }

 return res;

}

​

console.log( encodeBase64("This works") );

console.log( decodeBase64("VGhpcyA=d29ya3M=") );