code: function buildSingleFilterQueryObject(paginationFilter) {
    return function(submissionQueryField) {
      var fieldQuery = {
      };
  
      //formId and _id fields are ObjectIds. They must be valid in order to search for them.
      if (submissionQueryField === 'formId' || submissionQueryField === '_id') {
        if (mongoose.Types.ObjectId.isValid(paginationFilter)) {
          //Cannot use $regex when searching for ObjectIDs
          fieldQuery[submissionQueryField] = new mongoose.Types.ObjectId(paginationFilter);
        } else {
          //not a valid objectId, don't want to search for it.
          return null;
        }
      } else {
        fieldQuery[submissionQueryField] = {$regex: paginationFilter, $options: 'i'};
      }
  
      return fieldQuery;
    };
  }
docs: buildSingleFilterQueryObject - Building a query object based on the field to be queried
  
  @param  {string} paginationFilter     Filter value
  @return {object}                      Generated Query for the field