How to use pouchdb-mapreduce-utils - 10 common examples

}
      var newKeys = mapToKeysArray(indexableKeysToKeyValues);
      newKeys.forEach(function (key) {
        if (!oldKeys.has(key)) {
          // new doc
          var kvDoc = {
            _id: key
          };
          var keyValue = indexableKeysToKeyValues.get(key);
          if ('value' in keyValue) {
            kvDoc.value = keyValue.value;
          }
          kvDocs.push(kvDoc);
        }
      });
      metaDoc.keys = uniq(newKeys.concat(metaDoc.keys));
      kvDocs.push(metaDoc);

      return kvDocs;
    }

var finalResults;
      if (shouldReduce) {
        finalResults = reduceView(view, rows, opts);
      } else {
        finalResults = {
          total_rows: totalRows,
          offset: skip,
          rows: rows
        };
      }
      /* istanbul ignore if */
      if (opts.update_seq) {
        finalResults.update_seq = view.seq;
      }
      if (opts.include_docs) {
        var docIds = uniq(rows.map(rowToDocId));

        return view.sourceDB.allDocs({
          keys: docIds,
          include_docs: true,
          conflicts: opts.conflicts,
          attachments: opts.attachments,
          binary: opts.binary
        }).then(function (allDocsRes) {
          var docIdsToDocs = new Map();
          allDocsRes.rows.forEach(function (row) {
            docIdsToDocs.set(row.id, row.doc);
          });
          rows.forEach(function (row) {
            var docId = rowToDocId(row);
            var doc = docIdsToDocs.get(docId);
            if (doc) {

var row = kvDocsRes.rows[i];
        var doc = row.doc;
        if (!doc) { // deleted
          continue;
        }
        kvDocs.push(doc);
        oldKeys.add(doc._id);
        doc._deleted = !indexableKeysToKeyValues.has(doc._id);
        if (!doc._deleted) {
          var keyValue = indexableKeysToKeyValues.get(doc._id);
          if ('value' in keyValue) {
            doc.value = keyValue.value;
          }
        }
      }
      var newKeys = mapToKeysArray(indexableKeysToKeyValues);
      newKeys.forEach(function (key) {
        if (!oldKeys.has(key)) {
          // new doc
          var kvDoc = {
            _id: key
          };
          var keyValue = indexableKeysToKeyValues.get(key);
          if ('value' in keyValue) {
            kvDoc.value = keyValue.value;
          }
          kvDocs.push(kvDoc);
        }
      });
      metaDoc.keys = uniq(newKeys.concat(metaDoc.keys));
      kvDocs.push(metaDoc);

.then(function (lastSeqDoc) {
        var docIds = mapToKeysArray(docIdsToChangesAndEmits);
        return Promise.all(docIds.map(function (docId) {
          return getDocsToPersist(docId, view, docIdsToChangesAndEmits);
        })).then(function (listOfDocsToPersist) {
          var docsToPersist = flatten(listOfDocsToPersist);
          lastSeqDoc.seq = seq;
          docsToPersist.push(lastSeqDoc);
          // write all docs in a single operation, update the seq once
          return view.db.bulkDocs({docs : docsToPersist});
        });
      });
  }

return db.get('_local/' + localDocName).then(function (metaDoc) {
      var docsToViews = new Map();
      Object.keys(metaDoc.views).forEach(function (fullViewName) {
        var parts = parseViewName(fullViewName);
        var designDocName = '_design/' + parts[0];
        var viewName = parts[1];
        var views = docsToViews.get(designDocName);
        if (!views) {
          views = new Set();
          docsToViews.set(designDocName, views);
        }
        views.add(viewName);
      });
      var opts = {
        keys : mapToKeysArray(docsToViews),
        include_docs : true
      };
      return db.allDocs(opts).then(function (res) {
        var viewsToStatus = {};
        res.rows.forEach(function (row) {
          var ddocName = row.key.substring(8); // cuts off '_design/'
          docsToViews.get(row.key).forEach(function (viewName) {
            var fullViewName = ddocName + '/' + viewName;
            /* istanbul ignore if */
            if (!metaDoc.views[fullViewName]) {
              // new format, without slashes, to support PouchDB 2.2.0
              // migration test in pouchdb's browser.migration.js verifies this
              fullViewName = viewName;
            }
            var viewDBNames = Object.keys(metaDoc.views[fullViewName]);
            // design doc deleted, or view function nonexistent

return db.get('_design/' + designDocName).then(function (doc) {
        var fun = doc.views && doc.views[viewName];

        if (!fun) {
          // basic validator; it's assumed that every subclass would want this
          throw new NotFoundError('ddoc ' + doc._id + ' has no view named ' +
            viewName);
        }

        ddocValidator(doc, viewName);
        checkQueryParseError(opts, fun);

        var createViewPromise = createView(
          /* sourceDB */ db,
          /* viewName */ fullViewName,
          /* mapFun */ fun.map,
          /* reduceFun */ fun.reduce,
          /* temporary */ false,
          /* localDocName */ localDocName);
        return createViewPromise.then(function (view) {
          if (opts.stale === 'ok' || opts.stale === 'update_after') {
            if (opts.stale === 'update_after') {

opts = {};
    }
    opts = opts ? coerceOptions(opts) : {};

    if (typeof fun === 'function') {
      fun = {map : fun};
    }

    var promise = Promise.resolve().then(function () {
      return queryPromised(db, fun, opts);
    });
    promisedCallback(promise, callback);
    return promise;
  }

  var abstractViewCleanup = callbackify(function () {
    var db = this;
    /* istanbul ignore next */
    if (typeof db._viewCleanup === 'function') {
      return customViewCleanup(db);
    }
    if (isRemote(db)) {
      return httpViewCleanup(db);
    }
    return localViewCleanup(db);
  });

  return {
    query: abstractQuery,
    viewCleanup: abstractViewCleanup
  };
}

function checkQueryParseError(options, fun) {
    var startkeyName = options.descending ? 'endkey' : 'startkey';
    var endkeyName = options.descending ? 'startkey' : 'endkey';

    if (typeof options[startkeyName] !== 'undefined' &&
      typeof options[endkeyName] !== 'undefined' &&
      collate(options[startkeyName], options[endkeyName]) > 0) {
      throw new QueryParseError('No rows can match your key range, ' +
        'reverse your start_key and end_key or set {descending : true}');
    } else if (fun.reduce && options.reduce !== false) {
      if (options.include_docs) {
        throw new QueryParseError('{include_docs:true} is invalid for reduce');
      } else if (options.keys && options.keys.length > 1 &&
        !options.group && !options.group_level) {
        throw new QueryParseError('Multi-key fetches for reduce views must use ' +
          '{group: true}');
      }
    }
    ['group_level', 'limit', 'skip'].forEach(function (optionName) {
      var error = checkPositiveInteger(options[optionName]);
      if (error) {
        throw error;
      }
    });
  }

function checkPositiveInteger(number) {
    if (number) {
      if (typeof number !== 'number') {
        return  new QueryParseError('Invalid value for integer: "' +
          number + '"');
      }
      if (number < 0) {
        return new QueryParseError('Invalid value for positive integer: ' +
          '"' + number + '"');
      }
    }
  }

function checkQueryParseError(options, fun) {
    var startkeyName = options.descending ? 'endkey' : 'startkey';
    var endkeyName = options.descending ? 'startkey' : 'endkey';

    if (typeof options[startkeyName] !== 'undefined' &&
      typeof options[endkeyName] !== 'undefined' &&
      collate(options[startkeyName], options[endkeyName]) > 0) {
      throw new QueryParseError('No rows can match your key range, ' +
        'reverse your start_key and end_key or set {descending : true}');
    } else if (fun.reduce && options.reduce !== false) {
      if (options.include_docs) {
        throw new QueryParseError('{include_docs:true} is invalid for reduce');
      } else if (options.keys && options.keys.length > 1 &&
        !options.group && !options.group_level) {
        throw new QueryParseError('Multi-key fetches for reduce views must use ' +
          '{group: true}');
      }
    }
    ['group_level', 'limit', 'skip'].forEach(function (optionName) {
      var error = checkPositiveInteger(options[optionName]);
      if (error) {
        throw error;
      }
    });
  }