API Docs

Mongoose constructor.

The exports object of the mongoose module is an instance of this class. Most apps will only use this one instance.

Example:

const mongoose = require('mongoose');
mongoose instanceof mongoose.Mongoose; // true

// Create a new Mongoose instance with its own `connect()`, `set()`, `model()`, etc.
const m = new mongoose.Mongoose();

The Mongoose Aggregate constructor

The Mongoose CastError constructor

The Mongoose Collection constructor

The Mongoose Connection constructor

The Mongoose Date SchemaType.

Example:

const schema = new Schema({ test: Date });
schema.path('test') instanceof mongoose.Date; // true

The Mongoose Decimal128 SchemaType. Used for declaring paths in your schema that should be 128-bit decimal floating points. Do not use this to create a new Decimal128 instance, use mongoose.Types.Decimal128 instead.

Example:

const vehicleSchema = new Schema({ fuelLevel: mongoose.Decimal128 });

The Mongoose Document constructor.

The Mongoose DocumentProvider constructor. Mongoose users should not have to use this directly

The MongooseError constructor.

The Mongoose Mixed SchemaType. Used for declaring paths in your schema that Mongoose's change tracking, casting, and validation should ignore.

Example:

const schema = new Schema({ arbitrary: mongoose.Mixed });

The Mongoose Model constructor.

The Mongoose constructor

The exports of the mongoose module is an instance of this class.

Example:

const mongoose = require('mongoose');
const mongoose2 = new mongoose.Mongoose();

The Mongoose Number SchemaType. Used for declaring paths in your schema that Mongoose should cast to numbers.

Example:

const schema = new Schema({ num: mongoose.Number });
// Equivalent to:
const schema = new Schema({ num: 'number' });

The Mongoose ObjectId SchemaType. Used for declaring paths in your schema that should be MongoDB ObjectIds. Do not use this to create a new ObjectId instance, use mongoose.Types.ObjectId instead.

Example:

const childSchema = new Schema({ parentId: mongoose.ObjectId });

The Mongoose Promise constructor.

Storage layer for mongoose promises

The Mongoose Query constructor.

Expose connection states for user-land

The Mongoose Schema constructor

Example:

const mongoose = require('mongoose');
const Schema = mongoose.Schema;
const CatSchema = new Schema(..);

The Mongoose SchemaType constructor

The constructor used for schematype options

The various Mongoose SchemaTypes.

Note:

Alias of mongoose.Schema.Types for backwards compatibility.

The various Mongoose Types.

Example:

const mongoose = require('mongoose');
const array = mongoose.Types.Array;

Types:

• Array
• Buffer
• Embedded
• DocumentArray
• Decimal128
• ObjectId
• Map
• Subdocument

Using this exposed access to the ObjectId type, we can construct ids on demand.

const ObjectId = mongoose.Types.ObjectId;
const id1 = new ObjectId;

The Mongoose VirtualType constructor

Opens the default mongoose connection.

Example:

mongoose.connect('mongodb://user:pass@localhost:port/database');

// replica sets
const uri = 'mongodb://user:pass@localhost:port,anotherhost:port,yetanother:port/mydatabase';
mongoose.connect(uri);

// with options
mongoose.connect(uri, options);

// optional callback that gets fired when initial connection completed
const uri = 'mongodb://nonexistent.domain:27000';
mongoose.connect(uri, function(error) {
  // if error is truthy, the initial connection failed.
})

The Mongoose module's default connection. Equivalent to mongoose.connections[0], see connections.

Example:

const mongoose = require('mongoose');
mongoose.connect(...);
mongoose.connection.on('error', cb);

This is the connection used by default for every model created using mongoose.model.

To create a new connection, use createConnection().

An array containing all connections associated with this Mongoose instance. By default, there is 1 connection. Calling createConnection() adds a connection to this array.

Example:

const mongoose = require('mongoose');
mongoose.connections.length; // 1, just the default connection
mongoose.connections[0] === mongoose.connection; // true

mongoose.createConnection('mongodb://localhost:27017/test');
mongoose.connections.length; // 2

Creates a Connection instance.

Each connection instance maps to a single database. This method is helpful when managing multiple db connections.

Options passed take precedence over options included in connection strings.

Example:

// with mongodb:// URI
db = mongoose.createConnection('mongodb://user:pass@localhost:port/database');

// and options
const opts = { db: { native_parser: true }}
db = mongoose.createConnection('mongodb://user:pass@localhost:port/database', opts);

// replica sets
db = mongoose.createConnection('mongodb://user:pass@localhost:port,anotherhost:port,yetanother:port/database');

// and options
const opts = { replset: { strategy: 'ping', rs_name: 'testSet' }}
db = mongoose.createConnection('mongodb://user:pass@localhost:port,anotherhost:port,yetanother:port/database', opts);

// and options
const opts = { server: { auto_reconnect: false }, user: 'username', pass: 'mypassword' }
db = mongoose.createConnection('localhost', 'database', port, opts)

// initialize now, connect later
db = mongoose.createConnection();
db.openUri('localhost', 'database', port, [opts]);

Removes the model named name from the default connection, if it exists. You can use this function to clean up any models you created in your tests to prevent OverwriteModelErrors.

Equivalent to mongoose.connection.deleteModel(name).

Example:

mongoose.model('User', new Schema({ name: String }));
console.log(mongoose.model('User')); // Model object
mongoose.deleteModel('User');
console.log(mongoose.model('User')); // undefined

// Usually useful in a Mocha `afterEach()` hook
afterEach(function() {
  mongoose.deleteModel(/.+/); // Delete every model
});

Runs .close() on all connections in parallel.

Object with get() and set() containing the underlying driver this Mongoose instance uses to communicate with the database. A driver is a Mongoose-specific interface that defines functions like find().

Gets mongoose options

Example:

mongoose.get('test') // returns the 'test' value

Returns true if Mongoose can cast the given value to an ObjectId, or false otherwise.

Example:

mongoose.isValidObjectId(new mongoose.Types.ObjectId()); // true
mongoose.isValidObjectId('0123456789ab'); // true
mongoose.isValidObjectId(6); // false

Defines a model or retrieves it.

Models defined on the mongoose instance are available to all connection created by the same mongoose instance.

If you call mongoose.model() with twice the same name but a different schema, you will get an OverwriteModelError. If you call mongoose.model() with the same name and same schema, you'll get the same schema back.

Example:

const mongoose = require('mongoose');

// define an Actor model with this mongoose instance
const schema = new Schema({ name: String });
mongoose.model('Actor', schema);

// create a new connection
const conn = mongoose.createConnection(..);

// create Actor model
const Actor = conn.model('Actor', schema);
conn.model('Actor') === Actor; // true
conn.model('Actor', schema) === Actor; // true, same schema
conn.model('Actor', schema, 'actors') === Actor; // true, same schema and collection name

// This throws an `OverwriteModelError` because the schema is different.
conn.model('Actor', new Schema({ name: String }));

When no collection argument is passed, Mongoose uses the model name. If you don't like this behavior, either pass a collection name, use mongoose.pluralize(), or set your schemas collection name option.

Example:

const schema = new Schema({ name: String }, { collection: 'actor' });

// or

schema.set('collection', 'actor');

// or

const collectionName = 'actor'
const M = mongoose.model('Actor', schema, collectionName)

Returns an array of model names created on this instance of Mongoose.

Note:

Does not include names of models created using connection.model().

The node-mongodb-native driver Mongoose uses.

The mquery query builder Mongoose uses.

Mongoose uses this function to get the current time when setting timestamps. You may stub out this function using a tool like Sinon for testing.

Declares a global plugin executed on all Schemas.

Equivalent to calling .plugin(fn) on each Schema you create.

Getter/setter around function for pluralizing collection names.

Sets mongoose options

Example:

mongoose.set('test', value) // sets the 'test' option to `value`

mongoose.set('debug', true) // enable logging collection methods + arguments to the console/file

mongoose.set('debug', function(collectionName, methodName, ...methodArgs) {}); // use custom function to log collection methods + arguments

Currently supported options are

• 'debug': If true, prints the operations mongoose sends to MongoDB to the console. If a writable stream is passed, it will log to that stream, without colorization. If a callback function is passed, it will receive the collection name, the method name, then all arugments passed to the method. For example, if you wanted to replicate the default logging, you could output from the callback Mongoose: ${collectionName}.${methodName}(${methodArgs.join(', ')}).
• 'returnOriginal': If false, changes the default returnOriginal option to findOneAndUpdate(), findByIdAndUpdate, and findOneAndReplace() to false. This is equivalent to setting the new option to true for findOneAndX() calls by default. Read our findOneAndUpdate() tutorial for more information.
• 'bufferCommands': enable/disable mongoose's buffering mechanism for all connections and models
• 'useCreateIndex': false by default. Set to true to make Mongoose's default index build use createIndex() instead of ensureIndex() to avoid deprecation warnings from the MongoDB driver.
• 'useFindAndModify': true by default. Set to false to make findOneAndUpdate() and findOneAndRemove() use native findOneAndUpdate() rather than findAndModify().
• 'useNewUrlParser': false by default. Set to true to make all connections set the useNewUrlParser option by default
• 'useUnifiedTopology': false by default. Set to true to make all connections set the useUnifiedTopology option by default
• 'cloneSchemas': false by default. Set to true to clone() all schemas before compiling into a model.
• 'applyPluginsToDiscriminators': false by default. Set to true to apply global plugins to discriminator schemas. This typically isn't necessary because plugins are applied to the base schema and discriminators copy all middleware, methods, statics, and properties from the base schema.
• 'applyPluginsToChildSchemas': true by default. Set to false to skip applying global plugins to child schemas
• 'objectIdGetter': true by default. Mongoose adds a getter to MongoDB ObjectId's called _id that returns this for convenience with populate. Set this to false to remove the getter.
• 'runValidators': false by default. Set to true to enable update validators for all validators by default.
• 'toObject': { transform: true, flattenDecimals: true } by default. Overwrites default objects to toObject()
• 'toJSON': { transform: true, flattenDecimals: true } by default. Overwrites default objects to toJSON(), for determining how Mongoose documents get serialized by JSON.stringify()
• 'strict': true by default, may be false, true, or 'throw'. Sets the default strict mode for schemas.
• 'strictQuery': false by default, may be false, true, or 'throw'. Sets the default strictQuery mode for schemas.
• 'selectPopulatedPaths': true by default. Set to false to opt out of Mongoose adding all fields that you populate() to your select(). The schema-level option selectPopulatedPaths overwrites this one.
• 'typePojoToMixed': true by default, may be false or true. Sets the default typePojoToMixed for schemas.
• 'maxTimeMS': If set, attaches maxTimeMS to every query
• 'autoIndex': true by default. Set to false to disable automatic index creation for all models associated with this Mongoose instance.
• 'autoCreate': Set to true to make Mongoose call Model.createCollection() automatically when you create a model with mongoose.model() or conn.model(). This is useful for testing transactions, change streams, and other features that require the collection to exist.
• 'overwriteModels': Set to true to default to overwriting models with the same name when calling mongoose.model(), as opposed to throwing an OverwriteModelError.

Requires MongoDB >= 3.6.0. Starts a MongoDB session for benefits like causal consistency, retryable writes, and transactions.

Calling mongoose.startSession() is equivalent to calling mongoose.connection.startSession(). Sessions are scoped to a connection, so calling mongoose.startSession() starts a session on the default mongoose connection.

The Mongoose version

Example

console.log(mongoose.version); // '5.x.x'

Schema constructor.

Example:

const child = new Schema({ name: String });
const schema = new Schema({ name: String, age: Number, children: [child] });
const Tree = mongoose.model('Tree', schema);

// setting schema options
new Schema({ name: String }, { _id: false, autoIndex: false })

Options:

• autoIndex: bool - defaults to null (which means use the connection's autoIndex option)
• autoCreate: bool - defaults to null (which means use the connection's autoCreate option)
• bufferCommands: bool - defaults to true
• bufferTimeoutMS: number - defaults to 10000 (10 seconds). If bufferCommands is enabled, the amount of time Mongoose will wait for connectivity to be restablished before erroring out.
• capped: bool - defaults to false
• collection: string - no default
• id: bool - defaults to true
• _id: bool - defaults to true
• minimize: bool - controls document#toObject behavior when called manually - defaults to true
• read: string
• writeConcern: object - defaults to null, use to override the MongoDB server's default write concern settings
• shardKey: object - defaults to null
• strict: bool - defaults to true
• strictQuery: bool - defaults to false
• toJSON - object - no default
• toObject - object - no default
• typeKey - string - defaults to 'type'
• typePojoToMixed - boolean - defaults to true. Determines whether a type set to a POJO becomes a Mixed path or a Subdocument
• useNestedStrict - boolean - defaults to false
• validateBeforeSave - bool - defaults to true
• versionKey: string or object - defaults to "__v"
• optimisticConcurrency: bool - defaults to false. Set to true to enable optimistic concurrency.
• collation: object - defaults to null (which means use no collation)
• selectPopulatedPaths: boolean - defaults to true
• skipVersioning: object - paths to exclude from versioning
• timestamps: object or boolean - defaults to false. If true, Mongoose adds createdAt and updatedAt properties to your schema and manages those properties for you.
• storeSubdocValidationError: boolean - Defaults to true. If false, Mongoose will wrap validation errors in single nested document subpaths into a single validation error on the single nested subdoc's path.

Options for Nested Schemas:

• excludeIndexes: bool - defaults to false. If true, skip building indexes on this schema's paths.

Note:

When nesting schemas, (children in the example above), always declare the child schema first before passing it into its parent.

The various built-in Mongoose Schema Types.

Example:

const mongoose = require('mongoose');
const ObjectId = mongoose.Schema.Types.ObjectId;

Types:

• String
• Number
• Boolean | Bool
• Array
• Buffer
• Date
• ObjectId | Oid
• Mixed

Using this exposed access to the Mixed SchemaType, we can use them in our schema.

const Mixed = mongoose.Schema.Types.Mixed;
new mongoose.Schema({ _user: Mixed })

The allowed index types

Adds key path / schema type pairs to this schema.

Example:

const ToySchema = new Schema();
ToySchema.add({ name: 'string', color: 'string', price: 'number' });

const TurboManSchema = new Schema();
// You can also `add()` another schema and copy over all paths, virtuals,
// getters, setters, indexes, methods, and statics.
TurboManSchema.add(ToySchema).add({ year: Number });

Array of child schemas (from document arrays and single nested subdocs) and their corresponding compiled models. Each element of the array is an object with 2 properties: schema and model.

This property is typically only useful for plugin authors and advanced users. You do not need to interact with this property at all to use mongoose.

Returns a deep copy of the schema

Example:

const schema = new Schema({ name: String });
const clone = schema.clone();
clone === schema; // false
clone.path('name'); // SchemaString { ... }

Iterates the schemas paths similar to Array#forEach.

The callback is passed the pathname and the schemaType instance.

Example:

const userSchema = new Schema({ name: String, registeredAt: Date });
userSchema.eachPath((pathname, schematype) => {
  // Prints twice:
  // name SchemaString { ... }
  // registeredAt SchemaDate { ... }
  console.log(pathname, schematype);
});

Gets a schema option.

Example:

schema.get('strict'); // true
schema.set('strict', false);
schema.get('strict'); // false

Defines an index (most likely compound) for this schema.

Example

schema.index({ first: 1, last: -1 })

Returns a list of indexes that this schema declares, via schema.index() or by index: true in a path's options.

Example:

const userSchema = new Schema({
  email: { type: String, required: true, unique: true },
  registeredAt: { type: Date, index: true }
});

// [ [ { email: 1 }, { unique: true, background: true } ],
//   [ { registeredAt: 1 }, { background: true } ] ]
userSchema.indexes();

Loads an ES6 class into a schema. Maps setters + getters, static methods, and instance methods to schema virtuals, statics, and methods.

Example:

const md5 = require('md5');
const userSchema = new Schema({ email: String });
class UserClass {
  // `gravatarImage` becomes a virtual
  get gravatarImage() {
    const hash = md5(this.email.toLowerCase());
    return `https://www.gravatar.com/avatar/${hash}`;
  }

  // `getProfileUrl()` becomes a document method
  getProfileUrl() {
    return `https://mysite.com/${this.email}`;
  }

  // `findByEmail()` becomes a static
  static findByEmail(email) {
    return this.findOne({ email });
  }
}

// `schema` will now have a `gravatarImage` virtual, a `getProfileUrl()` method,
// and a `findByEmail()` static
userSchema.loadClass(UserClass);

Adds an instance method to documents constructed from Models compiled from this schema.

Example

const schema = kittySchema = new Schema(..);

schema.method('meow', function () {
  console.log('meeeeeoooooooooooow');
})

const Kitty = mongoose.model('Kitty', schema);

const fizz = new Kitty;
fizz.meow(); // meeeeeooooooooooooow

If a hash of name/fn pairs is passed as the only argument, each name/fn pair will be added as methods.

schema.method({
    purr: function () {}
  , scratch: function () {}
});

// later
fizz.purr();
fizz.scratch();

NOTE: Schema.method() adds instance methods to the Schema.methods object. You can also add instance methods directly to the Schema.methods object as seen in the guide

The original object passed to the schema constructor

Example:

const schema = new Schema({ a: String }).add({ b: String });
schema.obj; // { a: String }

Gets/sets schema paths.

Sets a path (if arity 2) Gets a path (if arity 1)

Example

schema.path('name') // returns a SchemaType
schema.path('name', Number) // changes the schemaType of `name` to Number

Returns the pathType of path for this schema.

Given a path, returns whether it is a real, virtual, nested, or ad-hoc/undefined path.

Example:

const s = new Schema({ name: String, nested: { foo: String } });
s.virtual('foo').get(() => 42);
s.pathType('name'); // "real"
s.pathType('nested'); // "nested"
s.pathType('foo'); // "virtual"
s.pathType('fail'); // "adhocOrUndefined"

The paths defined on this schema. The keys are the top-level paths in this schema, and the values are instances of the SchemaType class.

Example:

const schema = new Schema({ name: String }, { _id: false });
schema.paths; // { name: SchemaString { ... } }

schema.add({ age: Number });
schema.paths; // { name: SchemaString { ... }, age: SchemaNumber { ... } }

Returns a new schema that has the picked paths from this schema.

This method is analagous to Lodash's pick() function for Mongoose schemas.

Example:

const schema = Schema({ name: String, age: Number });
// Creates a new schema with the same `name` path as `schema`,
// but no `age` path.
const newSchema = schema.pick(['name']);

newSchema.path('name'); // SchemaString { ... }
newSchema.path('age'); // undefined

Registers a plugin for this schema.

Example:

const s = new Schema({ name: String });
s.plugin(schema => console.log(schema.path('name').path));
mongoose.model('Test', s); // Prints 'name'

Defines a post hook for the document

const schema = new Schema(..);
schema.post('save', function (doc) {
  console.log('this fired after a document was saved');
});

schema.post('find', function(docs) {
  console.log('this fired after you ran a find query');
});

schema.post(/Many$/, function(res) {
  console.log('this fired after you ran `updateMany()` or `deleteMany()`);
});

const Model = mongoose.model('Model', schema);

const m = new Model(..);
m.save(function(err) {
  console.log('this fires after the `post` hook');
});

m.find(function(err, docs) {
  console.log('this fires after the post find hook');
});

Defines a pre hook for the model.

Example

const toySchema = new Schema({ name: String, created: Date });

toySchema.pre('save', function(next) {
  if (!this.created) this.created = new Date;
  next();
});

toySchema.pre('validate', function(next) {
  if (this.name !== 'Woody') this.name = 'Woody';
  next();
});

// Equivalent to calling `pre()` on `find`, `findOne`, `findOneAndUpdate`.
toySchema.pre(/^find/, function(next) {
  console.log(this.getFilter());
});

// Equivalent to calling `pre()` on `updateOne`, `findOneAndUpdate`.
toySchema.pre(['updateOne', 'findOneAndUpdate'], function(next) {
  console.log(this.getFilter());
});

toySchema.pre('deleteOne', function() {
  // Runs when you call `Toy.deleteOne()`
});

toySchema.pre('deleteOne', { document: true }, function() {
  // Runs when you call `doc.deleteOne()`
});

Adds a method call to the queue.

Example:

schema.methods.print = function() { console.log(this); };
schema.queue('print', []); // Print the doc every one is instantiated

const Model = mongoose.model('Test', schema);
new Model({ name: 'test' }); // Prints '{"_id": ..., "name": "test" }'

Removes the given path (or [paths]).

Example:

const schema = new Schema({ name: String, age: Number });
schema.remove('name');
schema.path('name'); // Undefined
schema.path('age'); // SchemaNumber { ... }

Returns an Array of path strings that are required by this schema.

Example:

const s = new Schema({
  name: { type: String, required: true },
  age: { type: String, required: true },
  notes: String
});
s.requiredPaths(); // [ 'age', 'name' ]

Sets a schema option.

Example

schema.set('strict'); // 'true' by default
schema.set('strict', false); // Sets 'strict' to false
schema.set('strict'); // 'false'

Adds static "class" methods to Models compiled from this schema.

Example

const schema = new Schema(..);
// Equivalent to `schema.statics.findByName = function(name) {}`;
schema.static('findByName', function(name) {
  return this.find({ name: name });
});

const Drink = mongoose.model('Drink', schema);
await Drink.findByName('LaCroix');

If a hash of name/fn pairs is passed as the only argument, each name/fn pair will be added as statics.

Creates a virtual type with the given name.

Returns the virtual type with the given name.

Reserved document keys.

Keys in this object are names that are rejected in schema declarations because they conflict with Mongoose functionality. If you create a schema using new Schema() with one of these property names, Mongoose will throw an error.

• _posts
• _pres
• collection
• emit
• errors
• get
• init
• isModified
• isNew
• listeners
• modelName
• on
• once
• populated
• prototype
• remove
• removeListener
• save
• schema
• toObject
• validate

NOTE: Use of these terms as method names is permitted, but play at your own risk, as they may be existing mongoose document methods you are stomping on.

const schema = new Schema(..);
 schema.methods.init = function () {} // potentially breaking

Connection constructor

For practical reasons, a Connection equals a Db.

The MongoClient instance this connection uses to talk to MongoDB. Mongoose automatically sets this property when the connection is opened.

Closes the connection

Retrieves a collection, creating it if not cached.

Not typically needed by applications. Just talk to your collection through your model.

A hash of the collections associated with this connection

A hash of the global options that are associated with this connection

Helper for createCollection(). Will explicitly create the given collection with specified options. Used to create capped collections and views from mongoose.

Options are passed down without modification to the MongoDB driver's createCollection() function

The mongodb.Db instance, set when the connection is opened

Removes the model named name from this connection, if it exists. You can use this function to clean up any models you created in your tests to prevent OverwriteModelErrors.

Example:

conn.model('User', new Schema({ name: String }));
console.log(conn.model('User')); // Model object
conn.deleteModel('User');
console.log(conn.model('User')); // undefined

// Usually useful in a Mocha `afterEach()` hook
afterEach(function() {
  conn.deleteModel(/.+/); // Delete every model
});

Helper for dropCollection(). Will delete the given collection, including all documents and indexes.

Helper for dropDatabase(). Deletes the given database, including all collections, documents, and indexes.

Example:

const conn = mongoose.createConnection('mongodb://localhost:27017/mydb');
// Deletes the entire 'mydb' database
await conn.dropDatabase();

Gets the value of the option key. Equivalent to conn.options[key]

Example:

conn.get('test'); // returns the 'test' value

Returns the MongoDB driver MongoClient instance that this connection uses to talk to MongoDB.

Example:

const conn = await mongoose.createConnection('mongodb://localhost:27017/test');

conn.getClient(); // MongoClient { ... }

The host name portion of the URI. If multiple hosts, such as a replica set, this will contain the first host name in the URI

Example

mongoose.createConnection('mongodb://localhost:27017/mydb').host; // "localhost"

A number identifier for this connection. Used for debugging when you have multiple connections.

Example

// The default connection has `id = 0`
mongoose.connection.id; // 0

// If you create a new connection, Mongoose increments id
const conn = mongoose.createConnection();
conn.id; // 1

Defines or retrieves a model.

const mongoose = require('mongoose');
const db = mongoose.createConnection(..);
db.model('Venue', new Schema(..));
const Ticket = db.model('Ticket', new Schema(..));
const Venue = db.model('Venue');

When no collection argument is passed, Mongoose produces a collection name by passing the model name to the utils.toCollectionName method. This method pluralizes the name. If you don't like this behavior, either pass a collection name or set your schemas collection name option.

Example:

const schema = new Schema({ name: String }, { collection: 'actor' });

// or

schema.set('collection', 'actor');

// or

const collectionName = 'actor'
const M = conn.model('Actor', schema, collectionName)

Returns an array of model names created on this connection.

A POJO containing a map from model names to models. Contains all models that have been added to this connection using Connection#model().

Example

const conn = mongoose.createConnection();
const Test = conn.model('Test', mongoose.Schema({ name: String }));

Object.keys(conn.models).length; // 1
conn.models.Test === Test; // true

The name of the database this connection points to.

Example

mongoose.createConnection('mongodb://localhost:27017/mydb').name; // "mydb"

Opens the connection with a URI using MongoClient.connect().

The password specified in the URI

Example

mongoose.createConnection('mongodb://val:psw@localhost:27017/mydb').pass; // "psw"

Declares a plugin executed on all schemas you pass to conn.model()

Equivalent to calling .plugin(fn) on each schema you create.

Example:

const db = mongoose.createConnection('mongodb://localhost:27017/mydb');
db.plugin(() => console.log('Applied'));
db.plugins.length; // 1

db.model('Test', new Schema({})); // Prints "Applied"

The plugins that will be applied to all models created on this connection.

Example:

const db = mongoose.createConnection('mongodb://localhost:27017/mydb');
db.plugin(() => console.log('Applied'));
db.plugins.length; // 1

db.model('Test', new Schema({})); // Prints "Applied"

The port portion of the URI. If multiple hosts, such as a replica set, this will contain the port from the first host name in the URI.

Example

mongoose.createConnection('mongodb://localhost:27017/mydb').port; // 27017

Connection ready state

• 0 = disconnected
• 1 = connected
• 2 = connecting
• 3 = disconnecting

Each state change emits its associated event name.

Example

conn.on('connected', callback);
conn.on('disconnected', callback);

Sets the value of the option key. Equivalent to conn.options[key] = val

Supported options include

• maxTimeMS: Set maxTimeMS for all queries on this connection.
• useFindAndModify: Set to false to work around the findAndModify() deprecation warning

Example:

conn.set('test', 'foo');
conn.get('test'); // 'foo'
conn.options.test; // 'foo'

Set the MongoDB driver MongoClient instance that this connection uses to talk to MongoDB. This is useful if you already have a MongoClient instance, and want to reuse it.

Example:

const client = await mongodb.MongoClient.connect('mongodb://localhost:27017/test');

const conn = mongoose.createConnection().setClient(client);

conn.getClient(); // MongoClient { ... }
conn.readyState; // 1, means 'CONNECTED'

Requires MongoDB >= 3.6.0. Starts a MongoDB session for benefits like causal consistency, retryable writes, and transactions.

Example:

const session = await conn.startSession();
let doc = await Person.findOne({ name: 'Ned Stark' }, null, { session });
await doc.remove();
// `doc` will always be null, even if reading from a replica set
// secondary. Without causal consistency, it is possible to
// get a doc back from the below query if the query reads from a
// secondary that is experiencing replication lag.
doc = await Person.findOne({ name: 'Ned Stark' }, null, { session, readPreference: 'secondary' });

Requires MongoDB >= 3.6.0. Executes the wrapped async function in a transaction. Mongoose will commit the transaction if the async function executes successfully and attempt to retry if there was a retriable error.

Calls the MongoDB driver's session.withTransaction(), but also handles resetting Mongoose document state as shown below.

Example:

const doc = new Person({ name: 'Will Riker' });
await db.transaction(async function setRank(session) {
  doc.rank = 'Captain';
  await doc.save({ session });
  doc.isNew; // false

  // Throw an error to abort the transaction
  throw new Error('Oops!');
},{ readPreference: 'primary' }).catch(() => {});

// true, `transaction()` reset the document's state because the
// transaction was aborted.
doc.isNew;

Switches to a different database using the same connection pool.

Returns a new connection object, with the new db.

The username specified in the URI

Example

mongoose.createConnection('mongodb://val:psw@localhost:27017/mydb').user; // "val"

Watches the entire underlying database for changes. Similar to Model.watch().

This function does not trigger any middleware. In particular, it does not trigger aggregate middleware.

The ChangeStream object is an event emitter that emits the following events

• 'change': A change occurred, see below example
• 'error': An unrecoverable error occurred. In particular, change streams currently error out if they lose connection to the replica set primary. Follow this GitHub issue for updates.
• 'end': Emitted if the underlying stream is closed
• 'close': Emitted if the underlying stream is closed

Example:

const User = conn.model('User', new Schema({ name: String }));

const changeStream = conn.watch().on('change', data => console.log(data));

// Triggers a 'change' event on the change stream.
await User.create({ name: 'test' });

Get all subdocs (by bfs)

Don't run validation on this path or persist changes to this path.

Example:

doc.foo = null;
doc.$ignore('foo');
doc.save(); // changes to foo will not be persisted and validators won't be run

Checks if a path is set to its default.

Example

MyModel = mongoose.model('test', { name: { type: String, default: 'Val '} });
const m = new MyModel();
m.$isDefault('name'); // true

Getter/setter, determines whether the document was removed or not.

Example:

product.remove(function (err, product) {
  product.$isDeleted(); // true
  product.remove(); // no-op, doesn't send anything to the db

  product.$isDeleted(false);
  product.$isDeleted(); // false
  product.remove(); // will execute a remove against the db
})

Returns true if the given path is nullish or only contains empty objects. Useful for determining whether this subdoc will get stripped out by the minimize option.

Example:

const schema = new Schema({ nested: { foo: String } });
const Model = mongoose.model('Test', schema);
const doc = new Model({});
doc.$isEmpty('nested'); // true
doc.nested.$isEmpty(); // true

doc.nested.foo = 'bar';
doc.$isEmpty('nested'); // false
doc.nested.$isEmpty(); // false

Empty object that you can use for storing properties on the document. This is handy for passing data to middleware without conflicting with Mongoose internals.

Example:

schema.pre('save', function() {
  // Mongoose will set `isNew` to `false` if `save()` succeeds
  this.$locals.wasNew = this.isNew;
});

schema.post('save', function() {
  // Prints true if `isNew` was set before `save()`
  console.log(this.$locals.wasNew);
});

Marks a path as valid, removing existing validation errors.

A string containing the current operation that Mongoose is executing on this document. May be null, 'save', 'validate', or 'remove'.

Example:

const doc = new Model({ name: 'test' });
doc.$op; // null

const promise = doc.save();
doc.$op; // 'save'

await promise;
doc.$op; // null

Alias for parent(). If this document is a subdocument or populated document, returns the document's parent. Returns undefined otherwise.

Getter/setter around the session associated with this document. Used to automatically set session if you save() a doc that you got from a query with an associated session.

Example:

const session = MyModel.startSession();
const doc = await MyModel.findOne().session(session);
doc.$session() === session; // true
doc.$session(null);
doc.$session() === null; // true

If this is a top-level document, setting the session propagates to all child docs.

Alias for set(), used internally to avoid conflicts

Takes a populated field and returns it to its unpopulated state.

Example:

Model.findOne().populate('author').exec(function (err, doc) {
  console.log(doc.author.name); // Dr.Seuss
  console.log(doc.depopulate('author'));
  console.log(doc.author); // '5144cf8050f071d979c118a7'
})

If the path was not populated, this is a no-op.

Returns the list of paths that have been directly modified. A direct modified path is a path that you explicitly set, whether via doc.foo = 'bar', Object.assign(doc, { foo: 'bar' }), or doc.set('foo', 'bar').

A path a may be in modifiedPaths() but not in directModifiedPaths() because a child of a was directly modified.

Example

const schema = new Schema({ foo: String, nested: { bar: String } });
const Model = mongoose.model('Test', schema);
await Model.create({ foo: 'original', nested: { bar: 'original' } });

const doc = await Model.findOne();
doc.nested.bar = 'modified';
doc.directModifiedPaths(); // ['nested.bar']
doc.modifiedPaths(); // ['nested', 'nested.bar']

Returns true if this document is equal to another document.

Documents are considered equal when they have matching _ids, unless neither document has an _id, in which case this function falls back to using deepEqual().

Hash containing current validation errors.

Explicitly executes population and returns a promise. Useful for promises integration.

Example:

const promise = doc.
  populate('company').
  populate({
    path: 'notes',
    match: /airline/,
    select: 'text',
    model: 'modelName'
    options: opts
  }).
  execPopulate();

// summary
doc.execPopulate().then(resolve, reject);

// you can also use doc.execPopulate(options) as a shorthand for // doc.populate(options).execPopulate()

Example:

const promise = doc.execPopulate({ path: 'company', select: 'employees' });

// summary promise.then(resolve,reject);

Returns the value of a path.

Example

// path
doc.get('age') // 47

// dynamic casting to a string
doc.get('age', String) // "47"

Returns the changes that happened to the document in the format that will be sent to MongoDB.

Example:

const userSchema = new Schema({
  name: String,
  age: Number,
  country: String
});
const User = mongoose.model('User', userSchema);
const user = await User.create({
  name: 'Hafez',
  age: 25,
  country: 'Egypt'
});

// returns an empty object, no changes happened yet
user.getChanges(); // { }

user.country = undefined;
user.age = 26;

user.getChanges(); // { $set: { age: 26 }, { $unset: { country: 1 } } }

await user.save();

user.getChanges(); // { }

Modifying the object that getChanges() returns does not affect the document's change tracking state. Even if you delete user.getChanges().$set, Mongoose will still send a $set to the server.

The string version of this documents _id.

Note:

This getter exists on all documents by default. The getter can be disabled by setting the id option of its Schema to false at construction time.

new Schema({ name: String }, { id: false });

Initializes the document without setters or marking anything modified.

Called internally after a document is returned from mongodb. Normally, you do not need to call this function on your own.

This function triggers init middleware. Note that init hooks are synchronous.

Helper for console.log

Marks a path as invalid, causing validation to fail.

The errorMsg argument will become the message of the ValidationError.

The value argument (if passed) will be available through the ValidationError.value property.

doc.invalidate('size', 'must be less than 20', 14);

doc.validate(function (err) {
  console.log(err)
  // prints
  { message: 'Validation failed',
    name: 'ValidationError',
    errors:
     { size:
        { message: 'must be less than 20',
          name: 'ValidatorError',
          path: 'size',
          type: 'user defined',
          value: 14 } } }
})

Returns true if path was directly set and modified, else false.

Example

doc.set('documents.0.title', 'changed');
doc.isDirectModified('documents.0.title') // true
doc.isDirectModified('documents') // false

Checks if path was explicitly selected. If no projection, always returns true.

Example

Thing.findOne().select('nested.name').exec(function (err, doc) {
   doc.isDirectSelected('nested.name') // true
   doc.isDirectSelected('nested.otherName') // false
   doc.isDirectSelected('nested')  // false
})

Checks if path is in the init state, that is, it was set by Document#init() and not modified since.

Returns true if any of the given paths is modified, else false. If no arguments, returns true if any path in this document is modified.

If path is given, checks if a path or any full path containing path as part of its path chain has been modified.

Example

doc.set('documents.0.title', 'changed');
doc.isModified()                      // true
doc.isModified('documents')           // true
doc.isModified('documents.0.title')   // true
doc.isModified('documents otherProp') // true
doc.isDirectModified('documents')     // false

Boolean flag specifying if the document is new.

Checks if path was selected in the source query which initialized this document.

Example

Thing.findOne().select('name').exec(function (err, doc) {
   doc.isSelected('name') // true
   doc.isSelected('age')  // false
})

Marks the path as having pending changes to write to the db.

Very helpful when using Mixed types.

Example:

doc.mixed.type = 'changed';
doc.markModified('mixed.type');
doc.save() // changes to mixed.type are now persisted

Returns the list of paths that have been modified.

Overwrite all values in this document with the values of obj, except for immutable properties. Behaves similarly to set(), except for it unsets all properties that aren't in obj.

If this document is a subdocument or populated document, returns the document's parent. Returns undefined otherwise.

Populates document references, executing the callback when complete. If you want to use promises instead, use this function with execPopulate()

Example:

doc
.populate('company')
.populate({
  path: 'notes',
  match: /airline/,
  select: 'text',
  model: 'modelName'
  options: opts
}, function (err, user) {
  assert(doc._id === user._id) // the document itself is passed
})

// summary
doc.populate(path)                   // not executed
doc.populate(options);               // not executed
doc.populate(path, callback)         // executed
doc.populate(options, callback);     // executed
doc.populate(callback);              // executed
doc.populate(options).execPopulate() // executed, returns promise

NOTE:

Population does not occur unless a callback is passed or you explicitly call execPopulate(). Passing the same path a second time will overwrite the previous path options. See Model.populate() for explaination of options.

Gets _id(s) used during population of the given path.

Example:

Model.findOne().populate('author').exec(function (err, doc) {
  console.log(doc.author.name)         // Dr.Seuss
  console.log(doc.populated('author')) // '5144cf8050f071d979c118a7'
})

If the path was not populated, returns undefined.

Sends a replaceOne command with this document _id as the query selector.

Valid options:

• same as in Model.replaceOne

Saves this document by inserting a new document into the database if document.isNew is true, or sends an updateOne operation only with the modifications to the database, it does not replace the whole document in the latter case.

Example:

product.sold = Date.now();
product = await product.save();

If save is successful, the returned promise will fulfill with the document saved.

Example:

const newProduct = await product.save();
newProduct === product; // true

The document's schema.

Sets the value of a path, or many paths.

Example:

// path, value
doc.set(path, value)

// object
doc.set({
    path  : value
  , path2 : {
       path  : value
    }
})

// on-the-fly cast to number
doc.set(path, value, Number)

// on-the-fly cast to string
doc.set(path, value, String)

// changing strict mode behavior
doc.set(path, value, { strict: false });

The return value of this method is used in calls to JSON.stringify(doc).

This method accepts the same options as Document#toObject. To apply the options to every document of your schema by default, set your schemas toJSON option to the same argument.

schema.set('toJSON', { virtuals: true })

See schema options for details.

Converts this document into a plain-old JavaScript object (POJO).

Buffers are converted to instances of mongodb.Binary for proper storage.

Options:

• getters apply all getters (path and virtual getters), defaults to false
• aliases apply all aliases if virtuals=true, defaults to true
• virtuals apply virtual getters (can override getters option), defaults to false
• minimize remove empty objects, defaults to true
• transform a transform function to apply to the resulting document before returning
• depopulate depopulate any populated paths, replacing them with their original refs, defaults to false
• versionKey whether to include the version key, defaults to true
• flattenMaps convert Maps to POJOs. Useful if you want to JSON.stringify() the result of toObject(), defaults to false
• useProjection set to true to omit fields that are excluded in this document's projection. Unless you specified a projection, this will omit any field that has select: false in the schema.

Getters/Virtuals

Example of only applying path getters

doc.toObject({ getters: true, virtuals: false })

Example of only applying virtual getters

doc.toObject({ virtuals: true })

Example of applying both path and virtual getters

doc.toObject({ getters: true })

To apply these options to every document of your schema by default, set your schemas toObject option to the same argument.

schema.set('toObject', { virtuals: true })

Transform

We may need to perform a transformation of the resulting object based on some criteria, say to remove some sensitive information or return a custom object. In this case we set the optional transform function.

Transform functions receive three arguments

function (doc, ret, options) {}

• doc The mongoose document which is being converted
• ret The plain object representation which has been converted
• options The options in use (either schema options or the options passed inline)

Example

// specify the transform schema option
if (!schema.options.toObject) schema.options.toObject = {};
schema.options.toObject.transform = function (doc, ret, options) {
  // remove the _id of every document before returning the result
  delete ret._id;
  return ret;
}

// without the transformation in the schema
doc.toObject(); // { _id: 'anId', name: 'Wreck-it Ralph' }

// with the transformation
doc.toObject(); // { name: 'Wreck-it Ralph' }

With transformations we can do a lot more than remove properties. We can even return completely new customized objects:

if (!schema.options.toObject) schema.options.toObject = {};
schema.options.toObject.transform = function (doc, ret, options) {
  return { movie: ret.name }
}

// without the transformation in the schema
doc.toObject(); // { _id: 'anId', name: 'Wreck-it Ralph' }

// with the transformation
doc.toObject(); // { movie: 'Wreck-it Ralph' }

Note: if a transform function returns undefined, the return value will be ignored.

Transformations may also be applied inline, overridding any transform set in the options:

function xform (doc, ret, options) {
  return { inline: ret.name, custom: true }
}

// pass the transform as an inline option
doc.toObject({ transform: xform }); // { inline: 'Wreck-it Ralph', custom: true }

If you want to skip transformations, use transform: false:

schema.options.toObject.hide = '_id';
schema.options.toObject.transform = function (doc, ret, options) {
  if (options.hide) {
    options.hide.split(' ').forEach(function (prop) {
      delete ret[prop];
    });
  }
  return ret;
}

const doc = new Doc({ _id: 'anId', secret: 47, name: 'Wreck-it Ralph' });
doc.toObject();                                        // { secret: 47, name: 'Wreck-it Ralph' }
doc.toObject({ hide: 'secret _id', transform: false });// { _id: 'anId', secret: 47, name: 'Wreck-it Ralph' }
doc.toObject({ hide: 'secret _id', transform: true }); // { name: 'Wreck-it Ralph' }

If you pass a transform in toObject() options, Mongoose will apply the transform to subdocuments in addition to the top-level document. Similarly, transform: false skips transforms for all subdocuments.

Note that this is behavior is different for transforms defined in the schema

if you define a transform in schema.options.toObject.transform, that transform will not apply to subdocuments.

const memberSchema = new Schema({ name: String, email: String });
const groupSchema = new Schema({ members: [memberSchema], name: String, email });
const Group = mongoose.model('Group', groupSchema);

const doc = new Group({
  name: 'Engineering',
  email: 'dev@mongoosejs.io',
  members: [{ name: 'Val', email: 'val@mongoosejs.io' }]
});

// Removes `email` from both top-level document **and** array elements
// { name: 'Engineering', members: [{ name: 'Val' }] }
doc.toObject({ transform: (doc, ret) => { delete ret.email; return ret; } });

Transforms, like all of these options, are also available for toJSON. See this guide to JSON.stringify() to learn why toJSON() and toObject() are separate functions.

See schema options for some more details.

During save, no custom options are applied to the document before being sent to the database.

Helper for console.log

Gets all populated documents associated with this document.

Clears the modified state on the specified path.

Example:

doc.foo = 'bar';
doc.unmarkModified('foo');
doc.save(); // changes to foo will not be persisted

Sends an update command with this document _id as the query selector.

Example:

weirdCar.update({$inc: {wheels:1}}, { w: 1 }, callback);

Valid options:

• same as in Model.update

Sends an updateOne command with this document _id as the query selector.

Example:

weirdCar.updateOne({$inc: {wheels:1}}, { w: 1 }, callback);

Valid options:

• same as in Model.updateOne

Executes registered validation rules for this document.

Note:

This method is called pre save and if a validation rule is violated, save is aborted and the error is returned to your callback.

Example:

doc.validate(function (err) {
  if (err) handleError(err);
  else // validation passed
});

Executes registered validation rules (skipping asynchronous validators) for this document.

Note:

This method is useful if you need synchronous validation.

Example:

const err = doc.validateSync();
if (err) {
  handleError(err);
} else {
  // validation passed
}

A Model is a class that's your primary tool for interacting with MongoDB. An instance of a Model is called a Document.

In Mongoose, the term "Model" refers to subclasses of the mongoose.Model class. You should not use the mongoose.Model class directly. The mongoose.model() and connection.model() functions create subclasses of mongoose.Model as shown below.

Example:

// `UserModel` is a "Model", a subclass of `mongoose.Model`.
const UserModel = mongoose.model('User', new Schema({ name: String }));

// You can use a Model to create new documents using `new`:
const userDoc = new UserModel({ name: 'Foo' });
await userDoc.save();

// You also use a model to create queries:
const userFromDb = await UserModel.findOne({ name: 'Foo' });

Performs aggregations on the models collection.

If a callback is passed, the aggregate is executed and a Promise is returned. If a callback is not passed, the aggregate itself is returned.

This function triggers the following middleware.

• aggregate()

Example:

// Find the max balance of all accounts
Users.aggregate([
  { $group: { _id: null, maxBalance: { $max: '$balance' }}},
  { $project: { _id: 0, maxBalance: 1 }}
]).
then(function (res) {
  console.log(res); // [ { maxBalance: 98000 } ]
});

// Or use the aggregation pipeline builder.
Users.aggregate().
  group({ _id: null, maxBalance: { $max: '$balance' } }).
  project('-id maxBalance').
  exec(function (err, res) {
    if (err) return handleError(err);
    console.log(res); // [ { maxBalance: 98 } ]
  });

NOTE:

• Mongoose does not cast aggregation pipelines to the model's schema because $project and $group operators allow redefining the "shape" of the documents at any stage of the pipeline, which may leave documents in an incompatible format. You can use the mongoose-cast-aggregation plugin to enable minimal casting for aggregation pipelines.
• The documents returned are plain javascript objects, not mongoose documents (since any shape of document can be returned).

More About Aggregations:

• Mongoose Aggregate
• An Introduction to Mongoose Aggregate
• MongoDB Aggregation docs

Sends multiple insertOne, updateOne, updateMany, replaceOne, deleteOne, and/or deleteMany operations to the MongoDB server in one command. This is faster than sending multiple independent operations (e.g. if you use create()) because with bulkWrite() there is only one round trip to MongoDB.

Mongoose will perform casting on all operations you provide.

This function does not trigger any middleware, neither save(), nor update(). If you need to trigger save() middleware for every document use create() instead.

Example:

Character.bulkWrite([
  {
    insertOne: {
      document: {
        name: 'Eddard Stark',
        title: 'Warden of the North'
      }
    }
  },
  {
    updateOne: {
      filter: { name: 'Eddard Stark' },
      // If you were using the MongoDB driver directly, you'd need to do
      // `update: { $set: { title: ... } }` but mongoose adds $set for
      // you.
      update: { title: 'Hand of the King' }
    }
  },
  {
    deleteOne: {
      {
        filter: { name: 'Eddard Stark' }
      }
    }
  }
]).then(res => {
 // Prints "1 1 1"
 console.log(res.insertedCount, res.modifiedCount, res.deletedCount);
});

The supported operations are:

• insertOne
• updateOne
• updateMany
• deleteOne
• deleteMany
• replaceOne

Deletes all indexes that aren't defined in this model's schema. Used by syncIndexes().

The returned promise resolves to a list of the dropped indexes' names as an array

Counts number of documents that match filter in a database collection.

This method is deprecated. If you want to count the number of documents in a collection, e.g. count({}), use the estimatedDocumentCount() function instead. Otherwise, use the countDocuments() function instead.

Example:

Adventure.count({ type: 'jungle' }, function (err, count) {
  if (err) ..
  console.log('there are %d jungle adventures', count);
});

Counts number of documents matching filter in a database collection.

Example:

Adventure.countDocuments({ type: 'jungle' }, function (err, count) {
  console.log('there are %d jungle adventures', count);
});

If you want to count all documents in a large collection, use the estimatedDocumentCount() function instead. If you call countDocuments({}), MongoDB will always execute a full collection scan and not use any indexes.

The countDocuments() function is similar to count(), but there are a few operators that countDocuments() does not support. Below are the operators that count() supports but countDocuments() does not, and the suggested replacement:

• $where: $expr
• $near: $geoWithin with $center
• $nearSphere: $geoWithin with $centerSphere

Shortcut for saving one or more documents to the database. MyModel.create(docs) does new MyModel(doc).save() for every doc in docs.

This function triggers the following middleware.

• save()

Example:

// Insert one new `Character` document
await Character.create({ name: 'Jean-Luc Picard' });

// Insert multiple new `Character` documents
await Character.create([{ name: 'Will Riker' }, { name: 'Geordi LaForge' }]);

// Create a new character within a transaction. Note that you **must**
// pass an array as the first parameter to `create()` if you want to
// specify options.
await Character.create([{ name: 'Jean-Luc Picard' }], { session });

Create the collection for this model. By default, if no indexes are specified, mongoose will not create the collection for the model until any documents are created. Use this method to create the collection explicitly.

Note 1: You may need to call this before starting a transaction See https://docs.mongodb.com/manual/core/transactions/#transactions-and-operations

Note 2: You don't have to call this if your schema contains index or unique field. In that case, just use Model.init()

Example:

const userSchema = new Schema({ name: String })
const User = mongoose.model('User', userSchema);

User.createCollection().then(function(collection) {
  console.log('Collection is created!');
});

Similar to ensureIndexes(), except for it uses the createIndex function.

Deletes all of the documents that match conditions from the collection. Behaves like remove(), but deletes all documents that match conditions regardless of the single option.

Example:

await Character.deleteMany({ name: /Stark/, age: { $gte: 18 } });

Note:

This function triggers deleteMany query hooks. Read the middleware docs to learn more.

Deletes the first document that matches conditions from the collection. Behaves like remove(), but deletes at most one document regardless of the single option.

Example:

await Character.deleteOne({ name: 'Eddard Stark' });

Note:

This function triggers deleteOne query hooks. Read the middleware docs to learn more.

Adds a discriminator type.

Example:

function BaseSchema() {
  Schema.apply(this, arguments);

  this.add({
    name: String,
    createdAt: Date
  });
}
util.inherits(BaseSchema, Schema);

const PersonSchema = new BaseSchema();
const BossSchema = new BaseSchema({ department: String });

const Person = mongoose.model('Person', PersonSchema);
const Boss = Person.discriminator('Boss', BossSchema);
new Boss().__t; // "Boss". `__t` is the default `discriminatorKey`

const employeeSchema = new Schema({ boss: ObjectId });
const Employee = Person.discriminator('Employee', employeeSchema, 'staff');
new Employee().__t; // "staff" because of 3rd argument above

Creates a Query for a distinct operation.

Passing a callback executes the query.

Example

Link.distinct('url', { clicks: {$gt: 100}}, function (err, result) {
  if (err) return handleError(err);

  assert(Array.isArray(result));
  console.log('unique urls with more than 100 clicks', result);
})

const query = Link.distinct('url');
query.exec(callback);

Sends createIndex commands to mongo for each index declared in the schema. The createIndex commands are sent in series.

Example:

Event.ensureIndexes(function (err) {
  if (err) return handleError(err);
});

After completion, an index event is emitted on this Model passing an error if one occurred.

Example:

const eventSchema = new Schema({ thing: { type: 'string', unique: true }})
const Event = mongoose.model('Event', eventSchema);

Event.on('index', function (err) {
  if (err) console.error(err); // error occurred during index creation
})

NOTE: It is not recommended that you run this in production. Index creation may impact database performance depending on your load. Use with caution.

Estimates the number of documents in the MongoDB collection. Faster than using countDocuments() for large collections because estimatedDocumentCount() uses collection metadata rather than scanning the entire collection.

Example:

const numAdventures = Adventure.estimatedDocumentCount();

Event emitter that reports any errors that occurred. Useful for global error handling.

Example:

MyModel.events.on('error', err => console.log(err.message));

// Prints a 'CastError' because of the above handler
await MyModel.findOne({ _id: 'notanid' }).catch(noop);

Returns true if at least one document exists in the database that matches the given filter, and false otherwise.

Under the hood, MyModel.exists({ answer: 42 }) is equivalent to MyModel.findOne({ answer: 42 }).select({ _id: 1 }).lean().then(doc => !!doc)

Example:

await Character.deleteMany({});
await Character.create({ name: 'Jean-Luc Picard' });

await Character.exists({ name: /picard/i }); // true
await Character.exists({ name: /riker/i }); // false

This function triggers the following middleware.

• findOne()

Finds documents.

Mongoose casts the filter to match the model's schema before the command is sent. See our query casting tutorial for more information on how Mongoose casts filter.

Examples:

// find all documents
await MyModel.find({});

// find all documents named john and at least 18
await MyModel.find({ name: 'john', age: { $gte: 18 } }).exec();

// executes, passing results to callback
MyModel.find({ name: 'john', age: { $gte: 18 }}, function (err, docs) {});

// executes, name LIKE john and only selecting the "name" and "friends" fields
await MyModel.find({ name: /john/i }, 'name friends').exec();

// passing options
await MyModel.find({ name: /john/i }, null, { skip: 10 }).exec();

Finds a single document by its _id field. findById(id) is almost* equivalent to findOne({ _id: id }). If you want to query by a document's _id, use findById() instead of findOne().

The id is cast based on the Schema before sending the command.

This function triggers the following middleware.

• findOne()

* Except for how it treats undefined. If you use findOne(), you'll see that findOne(undefined) and findOne({ _id: undefined }) are equivalent to findOne({}) and return arbitrary documents. However, mongoose translates findById(undefined) into findOne({ _id: null }).

Example:

// Find the adventure with the given `id`, or `null` if not found
await Adventure.findById(id).exec();

// using callback
Adventure.findById(id, function (err, adventure) {});

// select only the adventures name and length
await Adventure.findById(id, 'name length').exec();

Issue a MongoDB findOneAndDelete() command by a document's _id field. In other words, findByIdAndDelete(id) is a shorthand for findOneAndDelete({ _id: id }).

This function triggers the following middleware.

• findOneAndDelete()

Issue a mongodb findAndModify remove command by a document's _id field. findByIdAndRemove(id, ...) is equivalent to findOneAndRemove({ _id: id }, ...).

Finds a matching document, removes it, passing the found document (if any) to the callback.

Executes the query if callback is passed.

This function triggers the following middleware.

• findOneAndRemove()

Options:

• sort: if multiple docs are found by the conditions, sets the sort order to choose which doc to update
• select: sets the document fields to return
• rawResult: if true, returns the raw result from the MongoDB driver
• strict: overwrites the schema's strict mode option for this update

Examples:

A.findByIdAndRemove(id, options, callback) // executes
A.findByIdAndRemove(id, options)  // return Query
A.findByIdAndRemove(id, callback) // executes
A.findByIdAndRemove(id) // returns Query
A.findByIdAndRemove()           // returns Query

Issues a mongodb findAndModify update command by a document's _id field. findByIdAndUpdate(id, ...) is equivalent to findOneAndUpdate({ _id: id }, ...).

Finds a matching document, updates it according to the update arg, passing any options, and returns the found document (if any) to the callback. The query executes if callback is passed.

This function triggers the following middleware.

• findOneAndUpdate()

Options:

• new: bool - true to return the modified document rather than the original. defaults to false
• upsert: bool - creates the object if it doesn't exist. defaults to false.
• runValidators: if true, runs update validators on this command. Update validators validate the update operation against the model's schema.
• setDefaultsOnInsert: if this and upsert are true, mongoose will apply the defaults specified in the model's schema if a new document is created. This option only works on MongoDB >= 2.4 because it relies on MongoDB's $setOnInsert operator.
• sort: if multiple docs are found by the conditions, sets the sort order to choose which doc to update
• select: sets the document fields to return
• rawResult: if true, returns the raw result from the MongoDB driver
• strict: overwrites the schema's strict mode option for this update

Examples:

A.findByIdAndUpdate(id, update, options, callback) // executes
A.findByIdAndUpdate(id, update, options)  // returns Query
A.findByIdAndUpdate(id, update, callback) // executes
A.findByIdAndUpdate(id, update)           // returns Query
A.findByIdAndUpdate()                     // returns Query

Note:

All top level update keys which are not atomic operation names are treated as set operations:

Example:

Model.findByIdAndUpdate(id, { name: 'jason bourne' }, options, callback)

// is sent as
Model.findByIdAndUpdate(id, { $set: { name: 'jason bourne' }}, options, callback)

This helps prevent accidentally overwriting your document with { name: 'jason bourne' }.

Note:

Values are cast to their appropriate types when using the findAndModify helpers. However, the below are not executed by default.

• defaults. Use the setDefaultsOnInsert option to override.

findAndModify helpers support limited validation. You can enable these by setting the runValidators options, respectively.

If you need full-fledged validation, use the traditional approach of first retrieving the document.

Model.findById(id, function (err, doc) {
  if (err) ..
  doc.name = 'jason bourne';
  doc.save(callback);
});

Finds one document.

The conditions are cast to their respective SchemaTypes before the command is sent.

Note: conditions is optional, and if conditions is null or undefined, mongoose will send an empty findOne command to MongoDB, which will return an arbitrary document. If you're querying by _id, use findById() instead.

Example:

// Find one adventure whose `country` is 'Croatia', otherwise `null`
await Adventure.findOne({ country: 'Croatia' }).exec();

// using callback
Adventure.findOne({ country: 'Croatia' }, function (err, adventure) {});

// select only the adventures name and length
await Adventure.findOne({ country: 'Croatia' }, 'name length').exec();

Issue a MongoDB findOneAndDelete() command.

Finds a matching document, removes it, and passes the found document (if any) to the callback.

Executes the query if callback is passed.

This function triggers the following middleware.

• findOneAndDelete()

This function differs slightly from Model.findOneAndRemove() in that findOneAndRemove() becomes a MongoDB findAndModify() command, as opposed to a findOneAndDelete() command. For most mongoose use cases, this distinction is purely pedantic. You should use findOneAndDelete() unless you have a good reason not to.

Options:

• sort: if multiple docs are found by the conditions, sets the sort order to choose which doc to update
• maxTimeMS: puts a time limit on the query - requires mongodb >= 2.6.0
• select: sets the document fields to return, ex. { projection: { _id: 0 } }
• projection: equivalent to select
• rawResult: if true, returns the raw result from the MongoDB driver
• strict: overwrites the schema's strict mode option for this update

Examples:

A.findOneAndDelete(conditions, options, callback) // executes
A.findOneAndDelete(conditions, options)  // return Query
A.findOneAndDelete(conditions, callback) // executes
A.findOneAndDelete(conditions) // returns Query
A.findOneAndDelete()           // returns Query

Values are cast to their appropriate types when using the findAndModify helpers. However, the below are not executed by default.

• defaults. Use the setDefaultsOnInsert option to override.

findAndModify helpers support limited validation. You can enable these by setting the runValidators options, respectively.

If you need full-fledged validation, use the traditional approach of first retrieving the document.

Model.findById(id, function (err, doc) {
  if (err) ..
  doc.name = 'jason bourne';
  doc.save(callback);
});

Issue a mongodb findAndModify remove command.

Finds a matching document, removes it, passing the found document (if any) to the callback.

Executes the query if callback is passed.

This function triggers the following middleware.

• findOneAndRemove()

Options:

• sort: if multiple docs are found by the conditions, sets the sort order to choose which doc to update
• maxTimeMS: puts a time limit on the query - requires mongodb >= 2.6.0
• select: sets the document fields to return
• projection: like select, it determines which fields to return, ex. { projection: { _id: 0 } }
• rawResult: if true, returns the raw result from the MongoDB driver
• strict: overwrites the schema's strict mode option for this update

Examples:

A.findOneAndRemove(conditions, options, callback) // executes
A.findOneAndRemove(conditions, options)  // return Query
A.findOneAndRemove(conditions, callback) // executes
A.findOneAndRemove(conditions) // returns Query
A.findOneAndRemove()           // returns Query

Values are cast to their appropriate types when using the findAndModify helpers. However, the below are not executed by default.

• defaults. Use the setDefaultsOnInsert option to override.

findAndModify helpers support limited validation. You can enable these by setting the runValidators options, respectively.

If you need full-fledged validation, use the traditional approach of first retrieving the document.

Model.findById(id, function (err, doc) {
  if (err) ..
  doc.name = 'jason bourne';
  doc.save(callback);
});

Issue a MongoDB findOneAndReplace() command.

Finds a matching document, replaces it with the provided doc, and passes the returned doc to the callback.

Executes the query if callback is passed.

This function triggers the following query middleware.

• findOneAndReplace()

Options:

• sort: if multiple docs are found by the conditions, sets the sort order to choose which doc to update
• maxTimeMS: puts a time limit on the query - requires mongodb >= 2.6.0
• select: sets the document fields to return
• projection: like select, it determines which fields to return, ex. { projection: { _id: 0 } }
• rawResult: if true, returns the raw result from the MongoDB driver
• strict: overwrites the schema's strict mode option for this update

Examples:

A.findOneAndReplace(conditions, options, callback) // executes
A.findOneAndReplace(conditions, options)  // return Query
A.findOneAndReplace(conditions, callback) // executes
A.findOneAndReplace(conditions) // returns Query
A.findOneAndReplace()           // returns Query

Values are cast to their appropriate types when using the findAndModify helpers. However, the below are not executed by default.

• defaults. Use the setDefaultsOnInsert option to override.

Issues a mongodb findAndModify update command.

Finds a matching document, updates it according to the update arg, passing any options, and returns the found document (if any) to the callback. The query executes if callback is passed else a Query object is returned.

Options:

• new: bool - if true, return the modified document rather than the original. defaults to false (changed in 4.0)
• upsert: bool - creates the object if it doesn't exist. defaults to false.
• overwrite: bool - if true, replace the entire document.
• fields: {Object|String} - Field selection. Equivalent to .select(fields).findOneAndUpdate()
• maxTimeMS: puts a time limit on the query - requires mongodb >= 2.6.0
• sort: if multiple docs are found by the conditions, sets the sort order to choose which doc to update
• runValidators: if true, runs update validators on this command. Update validators validate the update operation against the model's schema.
• setDefaultsOnInsert: if this and upsert are true, mongoose will apply the defaults specified in the model's schema if a new document is created. This option only works on MongoDB >= 2.4 because it relies on MongoDB's $setOnInsert operator.
• rawResult: if true, returns the raw result from the MongoDB driver
• strict: overwrites the schema's strict mode option for this update

Examples:

A.findOneAndUpdate(conditions, update, options, callback) // executes
A.findOneAndUpdate(conditions, update, options)  // returns Query
A.findOneAndUpdate(conditions, update, callback) // executes
A.findOneAndUpdate(conditions, update)           // returns Query
A.findOneAndUpdate()                             // returns Query

Note:

All top level update keys which are not atomic operation names are treated as set operations:

Example:

const query = { name: 'borne' };
Model.findOneAndUpdate(query, { name: 'jason bourne' }, options, callback)

// is sent as
Model.findOneAndUpdate(query, { $set: { name: 'jason bourne' }}, options, callback)

This helps prevent accidentally overwriting your document with { name: 'jason bourne' }.

Note:

Values are cast to their appropriate types when using the findAndModify helpers. However, the below are not executed by default.

• defaults. Use the setDefaultsOnInsert option to override.

findAndModify helpers support limited validation. You can enable these by setting the runValidators options, respectively.

If you need full-fledged validation, use the traditional approach of first retrieving the document.

Model.findById(id, function (err, doc) {
  if (err) ..
  doc.name = 'jason bourne';
  doc.save(callback);
});

Implements $geoSearch functionality for Mongoose

This function does not trigger any middleware

Example:

const options = { near: [10, 10], maxDistance: 5 };
Locations.geoSearch({ type : "house" }, options, function(err, res) {
  console.log(res);
});

Options:

• near {Array} x,y point to search for
• maxDistance {Number} the maximum distance from the point near that a result can be
• limit {Number} The maximum number of results to return
• lean {Object|Boolean} return the raw object instead of the Mongoose Model

Shortcut for creating a new Document from existing raw data, pre-saved in the DB. The document returned has no paths marked as modified initially.

Example:

// hydrate previous data into a Mongoose document
const mongooseCandy = Candy.hydrate({ _id: '54108337212ffb6d459f854c', type: 'jelly bean' });

This function is responsible for building indexes, unless autoIndex is turned off.

Mongoose calls this function automatically when a model is created using mongoose.model() or connection.model(), so you don't need to call it. This function is also idempotent, so you may call it to get back a promise that will resolve when your indexes are finished building as an alternative to MyModel.on('index')

Example:

const eventSchema = new Schema({ thing: { type: 'string', unique: true }})
// This calls `Event.init()` implicitly, so you don't need to call
// `Event.init()` on your own.
const Event = mongoose.model('Event', eventSchema);

Event.init().then(function(Event) {
  // You can also use `Event.on('index')` if you prefer event emitters
  // over promises.
  console.log('Indexes are done building!');
});

Shortcut for validating an array of documents and inserting them into MongoDB if they're all valid. This function is faster than .create() because it only sends one operation to the server, rather than one for each document.

Mongoose always validates each document before sending insertMany to MongoDB. So if one document has a validation error, no documents will be saved, unless you set the ordered option to false.

This function does not trigger save middleware.

This function triggers the following middleware.

• insertMany()

Example:

const arr = [{ name: 'Star Wars' }, { name: 'The Empire Strikes Back' }];
Movies.insertMany(arr, function(error, docs) {});

Helper for console.log. Given a model named 'MyModel', returns the string 'Model { MyModel }'.

Example:

const MyModel = mongoose.model('Test', Schema({ name: String }));
MyModel.inspect(); // 'Model { Test }'
console.log(MyModel); // Prints 'Model { Test }'

Lists the indexes currently defined in MongoDB. This may or may not be the same as the indexes defined in your schema depending on whether you use the autoIndex option and if you build indexes manually.

Executes a mapReduce command.

o is an object specifying all mapReduce options as well as the map and reduce functions. All options are delegated to the driver implementation. See node-mongodb-native mapReduce() documentation for more detail about options.

This function does not trigger any middleware.

Example:

const o = {};
// `map()` and `reduce()` are run on the MongoDB server, not Node.js,
// these functions are converted to strings
o.map = function () { emit(this.name, 1) };
o.reduce = function (k, vals) { return vals.length };
User.mapReduce(o, function (err, results) {
  console.log(results)
})

Other options:

• query {Object} query filter object.
• sort {Object} sort input objects using this key
• limit {Number} max number of documents
• keeptemp {Boolean, default:false} keep temporary data
• finalize {Function} finalize function
• scope {Object} scope variables exposed to map/reduce/finalize during execution
• jsMode {Boolean, default:false} it is possible to make the execution stay in JS. Provided in MongoDB > 2.0.X
• verbose {Boolean, default:false} provide statistics on job execution time.
• readPreference {String}
• out* {Object, default: {inline:1}} sets the output target for the map reduce job.

* out options:

• {inline:1} the results are returned in an array
• {replace: 'collectionName'} add the results to collectionName: the results replace the collection
• {reduce: 'collectionName'} add the results to collectionName: if dups are detected, uses the reducer / finalize functions
• {merge: 'collectionName'} add the results to collectionName: if dups exist the new docs overwrite the old

If options.out is set to replace, merge, or reduce, a Model instance is returned that can be used for further querying. Queries run against this model are all executed with the lean option; meaning only the js object is returned and no Mongoose magic is applied (getters, setters, etc).

Example:

const o = {};
// You can also define `map()` and `reduce()` as strings if your
// linter complains about `emit()` not being defined
o.map = 'function () { emit(this.name, 1) }';
o.reduce = 'function (k, vals) { return vals.length }';
o.out = { replace: 'createdCollectionNameForResults' }
o.verbose = true;

User.mapReduce(o, function (err, model, stats) {
  console.log('map reduce took %d ms', stats.processtime)
  model.find().where('value').gt(10).exec(function (err, docs) {
    console.log(docs);
  });
})

// `mapReduce()` returns a promise. However, ES6 promises can only
// resolve to exactly one value,
o.resolveToObject = true;
const promise = User.mapReduce(o);
promise.then(function (res) {
  const model = res.model;
  const stats = res.stats;
  console.log('map reduce took %d ms', stats.processtime)
  return model.find().where('value').gt(10).exec();
}).then(function (docs) {
   console.log(docs);
}).then(null, handleError).end()

Populates document references.

Available top-level options:

• path: space delimited path(s) to populate
• select: optional fields to select
• match: optional query conditions to match
• model: optional name of the model to use for population
• options: optional query options like sort, limit, etc
• justOne: optional boolean, if true Mongoose will always set path to an array. Inferred from schema by default.

Examples:

// populates a single object
User.findById(id, function (err, user) {
  const opts = [
    { path: 'company', match: { x: 1 }, select: 'name' },
    { path: 'notes', options: { limit: 10 }, model: 'override' }
  ];

  User.populate(user, opts, function (err, user) {
    console.log(user);
  });
});

// populates an array of objects
User.find(match, function (err, users) {
  const opts = [{ path: 'company', match: { x: 1 }, select: 'name' }];

  const promise = User.populate(users, opts);
  promise.then(console.log).end();
})

// imagine a Weapon model exists with two saved documents:
//   { _id: 389, name: 'whip' }
//   { _id: 8921, name: 'boomerang' }
// and this schema:
// new Schema({
//   name: String,
//   weapon: { type: ObjectId, ref: 'Weapon' }
// });

const user = { name: 'Indiana Jones', weapon: 389 };
Weapon.populate(user, { path: 'weapon', model: 'Weapon' }, function (err, user) {
  console.log(user.weapon.name); // whip
})

// populate many plain objects
const users = [{ name: 'Indiana Jones', weapon: 389 }]
users.push({ name: 'Batman', weapon: 8921 })
Weapon.populate(users, { path: 'weapon' }, function (err, users) {
  users.forEach(function (user) {
    console.log('%s uses a %s', users.name, user.weapon.name)
    // Indiana Jones uses a whip
    // Batman uses a boomerang
  });
});
// Note that we didn't need to specify the Weapon model because
// it is in the schema's ref

Additional properties to attach to the query when calling save() and isNew is false.