gistfile1.js

query = new Riak.Query();
query.input = 'people';

query.addMapper(function(value, keyData, arg) {
  if (value.age && value.age < 18) {
    return [value];
  } else {
    return [];
  }
});

query.addMapper(function(value, keyData, arg) {
  if (value.address && value.address.state) {
    return [{value.address.state: 1}];
  } 
  else {
    return [];
  }
});

query.addReducer(function(acc, item) {
  for (state in item) {
    if (acc[state]) {
      acc[state] += item[state];
    } else {
      acc[state] = item[state]
    }
  }
  
  return acc;
});

gistfile2.js

new Riak.Query(
  input: 'people',
  mappers: [
    function(value, keyData, arg) {
      if (value.age && value.age < 18) {
        return [value];
      } else {
        return [];
      }
    },
    
    function(value, keyData, arg) {
      if (value.address && value.address.state) {
        return [{value.address.state: 1}];
      } 
      else {
        return [];
      }
    }
  ],
  
  reducers: [
    function(acc, item) {
      for (state in item) {
        if (acc[state]) {
          acc[state] += item[state];
        } else {
          acc[state] = item[state]
        }
      }

      return acc;
    }
  ]
);