docs: function encode(number) {
          if (number === 0) {
              return '';
          }
  
          var quotient = Math.floor(number / 64);
          var remainder = number % 64;
  
          var digit;
          if (remainder < 10) {
              digit = '' + remainder;
          }
          else if (remainder < 36) {
              digit = String.fromCharCode(remainder + 55);
          }
          else if (remainder < 62) {
              digit = String.fromCharCode(remainder + 61);
          }
          else if (remainder === 62) {
              digit = '-';
          }
          else if (remainder === 63) {
              digit = '_';
          }
  
          return encode(quotient) + '' + digit;
      }