example of using commonjs to separate transformation logic from the map function itself

gistfile1.js

{
  views: {
    gender: {
      map: function(doc){
        var lib = require('/views/lib/transform')
          , key_value = lib.gender(doc);
        emit(key_value[0], key_value[1]);
        
      }
    },
    lib: {
      transform: {
        exports.gender = function(doc){
          // the default column is "gender"
          var key = 'gender'
            , value;
          // for different datasets, we write different rules
          if(doc.dataset_id === '...'){
            // let's say this dataset uses "gender" as the column
            // but uses 0 and 1 as values, where 1 is male and 0 is female
            switch(doc[key]){
              case 0:
                value = 'M';
                break;
              case 1:
                value = 'F';
                break;
            }
          } else if(doc.dataset_id === '...'){
            // this dataset uses "sex" as the column
            value = doc.sex;
          } else {
            // if no special rules, just grab the value
            value = doc[key];
          }
          return [key, value];
        } 
      }
    }
  }
}