code: function encode(str) {
      var i;
      var vacs = findSingleVacancies(str, singleLen + complexLen);
      var singleReplacements = vacs.slice(0, singleLen);
      var complexReplacements = vacs.slice(singleLen);
      var dest = str;
      // first replace complex delimiters
      for (i = COMPLEX_DELIMITERS.length - 1; i >= 0; i--) {
          if (i < complexReplacements.length) {
              dest = dest.split(COMPLEX_DELIMITERS[i]).join(complexReplacements[i]);
          }
      }
      // then replace single delimiters
      for (i = 0; i < singleReplacements.length; i++) {
          dest = dest.split(SINGLE_DELIMITERS[i]).join(singleReplacements[i]);
      }
      // concatenate with replacement map
      dest = singleReplacements.join('') + SECTION_DELIMITER + complexReplacements.join('') + SECTION_DELIMITER + dest;
      return dest;
  }
docs: Encode JSON string
  @param {string} str
  @returns {string}