text: var utf8Decode = require('utf8-decode');
  var keyStr = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';
  
  module.exports = decode;
  function decode(input) {
      var output = '';
      var chr1, chr2, chr3;
      var enc1, enc2, enc3, enc4;
      var i = 0;
  
      input = input.replace(/[^A-Za-z0-9\+\/\=]/g, '');
  
      while (i < input.length) {
  
          enc1 = keyStr.indexOf(input.charAt(i++));
          enc2 = keyStr.indexOf(input.charAt(i++));
          enc3 = keyStr.indexOf(input.charAt(i++));
          enc4 = keyStr.indexOf(input.charAt(i++));
  
          chr1 = (enc1 << 2) | (enc2 >> 4);
          chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
          chr3 = ((enc3 & 3) << 6) | enc4;
  
          output = output + String.fromCharCode(chr1);
  
          if (enc3 != 64) {
              output = output + String.fromCharCode(chr2);
          }
          if (enc4 != 64) {
              output = output + String.fromCharCode(chr3);
          }
  
      }
  
      output = utf8Decode(output);
  
      return output;
  
  }