multiple

curl http://localhost:5984/mydb/aSpecificDocId
// Take properties from aSpecificDocId which are keys for the following query
curl http://localhost:5984/mydb/_all_docs?keys=["docIdA","docIdB","docIdC","docIdD","docIdE"]

single.js

// curl http://localhost:5984/mydb/_design/mydoc/_view/fetch?startkey=["aSpecificDocId","a"]&endkey=["aSpecificDocId","z"]&include_docs=true

{
  map: function(doc) {
    if ('thing' === doc.type) {
      emit([doc._id, doc._id], doc);
      emit([doc._id, 'a'], {_id: doc.a});
      emit([doc._id, 'b'], {_id: doc.b});
      emit([doc._id, 'c'], {_id: doc.c});
      emit([doc._id, 'd'], {_id: doc.d});
      emit([doc._id, 'e'], {_id: doc.e});
    }
  }
}