var keyStr = "ABCDEFGHIJKLMNOP" +
            "QRSTUVWXYZabcdef" +
            "ghijklmnopqrstuv" +
            "wxyz0123456789+/" +
            "=";

function encode(input) {
  var output = "";
  var chr1, chr2, chr3 = "";
  var enc1, enc2, enc3, enc4 = "";
  var i = 0;

  do {
     chr1 = input.charCodeAt(i++);
     chr2 = input.charCodeAt(i++);
     chr3 = input.charCodeAt(i++);

     enc1 = chr1 >> 2;
     enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);
     enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);
     enc4 = chr3 & 63;

     if (isNaN(chr2)) {
        enc3 = enc4 = 64;
     } else if (isNaN(chr3)) {
        enc4 = 64;
     }

     output = output + 
        keyStr.charAt(enc1) + 
        keyStr.charAt(enc2) + 
        keyStr.charAt(enc3) + 
        keyStr.charAt(enc4);
     chr1 = chr2 = chr3 = "";
     enc1 = enc2 = enc3 = enc4 = "";
  } while (i < input.length);

  return output;
}