Perfect ATOB/BTOA alternatives (Base64 encoder/decoder) for JavaScript/Jscript.net Demo on http://jsfiddle.net/1okoy0r0/

base64-encode-decode.js

function b2a(a) {
  var c, d, e, f, g, h, i, j, o, b = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=", k = 0, l = 0, m = "", n = [];
  if (!a) return a;
  do c = a.charCodeAt(k++), d = a.charCodeAt(k++), e = a.charCodeAt(k++), j = c << 16 | d << 8 | e, 
  f = 63 & j >> 18, g = 63 & j >> 12, h = 63 & j >> 6, i = 63 & j, n[l++] = b.charAt(f) + b.charAt(g) + b.charAt(h) + b.charAt(i); while (k < a.length);
  return m = n.join(""), o = a.length % 3, (o ? m.slice(0, o - 3) :m) + "===".slice(o || 3);
}

function a2b(a) {
  var b, c, d, e = {}, f = 0, g = 0, h = "", i = String.fromCharCode, j = a.length;
  for (b = 0; 64 > b; b++) e["ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".charAt(b)] = b;
  for (c = 0; j > c; c++) for (b = e[a.charAt(c)], f = (f << 6) + b, g += 6; g >= 8; ) ((d = 255 & f >>> (g -= 8)) || j - 2 > c) && (h += i(d));
  return h;
}

/*
var str1ng="http://www.whak.ca/packer/",

encoded=b2a(str1ng),

decoded=a2b(encoded);

alert(encoded+"\n"+decoded);
*/