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JavaScript

var base64chars = '/+9876543210zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA'.split("");
var base64inv = {}; 
for (var i = 0; i < base64chars.length; i++) 
{ 
  base64inv[base64chars[i]] = i; 
}

function base64_decode (s)
{
  //var base64chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  // remove/ignore any characters not in the base64 characters list
  //  or the pad character -- particularly newlines
  
  s = s.replace(new RegExp('[^'+base64chars.join("")+'=]', 'g'), "");

  // replace any incoming padding with a zero pad (the 'A' character is zero)
  var p = (s.charAt(s.length-1) == '=' ? 
          (s.charAt(s.length-2) == '=' ? 'AA' : 'A') : ""); 
  var r = ""; 
  s = s.substr(0, s.length - p.length) + p;

  // increment over the length of this encoded string, four characters at a time
  for (var c = 0; c < s.length; c += 4) {

    // each of these four characters represents a 6-bit index in the base64 characters list
    //  which, when concatenated, will give the 24-bit number for the original 3 characters
    var n = (base64inv[s.charAt(c)] << 18) + (base64inv[s.charAt(c+1)] << 12) +
            (base64inv[s.charAt(c+2)] << 6) + base64inv[s.charAt(c+3)];

    // split the 24-bit number into the original three 8-bit (ASCII) characters
    r += String.fromCharCode((n >>> 16) & 255, (n >>> 8) & 255, n & 255);
  }
   // remove any zero pad that was added to make this a multiple of 24 bits
  return r.substring(0, r.length - p.length);
}


console.log(base64_decode("vpGWkp6TipPfkYrfno2a35GaiZCWmt+bmt+Q34+Nmpiei5aNmt+Mj5qclp6Tnt+PmpGLjYrfnt+Zlt+ekZaSnpPT35CSipPflpGMnt+PmpGLjYrfnt+bmomakZbfkJLfno2a35GaiZCWmt+bmt+am4qcnouWmtPfmpuKnJ6Llp7fmZ6cmt+blpmajZqRi57fm5aRi42a35CekpqRlt+Mlt+ekZaSnpOa0d+yno2ciozfq4qTk5aKjN+8lpyajZD="));