Class MongoClient

The MongoClient class is a class that allows for making Connections to MongoDB.

Remarks

The programmatically provided options take precedence over the URI options.

Example

import { MongoClient } from 'mongodb';

// Enable command monitoring for debugging
const client = new MongoClient('mongodb://localhost:27017', { monitorCommands: true });

client.on('commandStarted', started => console.log(started));
client.db().collection('pets');
await client.insertOne({ name: 'spot', kind: 'dog' });

Hierarchy

Constructors

Properties

captureRejectionSymbol: typeof captureRejectionSymbol
captureRejections: boolean

Sets or gets the default captureRejection value for all emitters.

defaultMaxListeners: number
errorMonitor: typeof errorMonitor

This symbol shall be used to install a listener for only monitoring 'error' events. Listeners installed using this symbol are called before the regular 'error' listeners are called.

Installing a listener using this symbol does not change the behavior once an 'error' event is emitted, therefore the process will still crash if no regular 'error' listener is installed.

Accessors

Methods

  • Close the client and its underlying connections

    Parameters

    • force: boolean = false

      Force close, emitting no events

    Returns Promise<void>

  • Create a new Db instance sharing the current socket connections.

    Parameters

    • Optional dbName: string

      The name of the database we want to use. If not provided, use database name from connection string.

    • Optional options: DbOptions

      Optional settings for Db construction

    Returns Db

  • Type Parameters

    • EventKey extends "error" | "timeout" | "close" | "open" | "serverOpening" | "serverClosed" | "serverDescriptionChanged" | "topologyOpening" | "topologyClosed" | "topologyDescriptionChanged" | "connectionPoolCreated" | "connectionPoolClosed" | "connectionPoolCleared" | "connectionPoolReady" | "connectionCreated" | "connectionReady" | "connectionClosed" | "connectionCheckOutStarted" | "connectionCheckOutFailed" | "connectionCheckedOut" | "connectionCheckedIn" | "commandStarted" | "commandSucceeded" | "commandFailed" | "serverHeartbeatStarted" | "serverHeartbeatSucceeded" | "serverHeartbeatFailed"

    Parameters

    Returns boolean

  • Type Parameters

    • EventKey extends "error" | "timeout" | "close" | "open" | "serverOpening" | "serverClosed" | "serverDescriptionChanged" | "topologyOpening" | "topologyClosed" | "topologyDescriptionChanged" | "connectionPoolCreated" | "connectionPoolClosed" | "connectionPoolCleared" | "connectionPoolReady" | "connectionCreated" | "connectionReady" | "connectionClosed" | "connectionCheckOutStarted" | "connectionCheckOutFailed" | "connectionCheckedOut" | "connectionCheckedIn" | "commandStarted" | "commandSucceeded" | "commandFailed" | "serverHeartbeatStarted" | "serverHeartbeatSucceeded" | "serverHeartbeatFailed"

    Parameters

    • type: string | symbol | EventKey

    Returns number

  • Type Parameters

    • EventKey extends "error" | "timeout" | "close" | "open" | "serverOpening" | "serverClosed" | "serverDescriptionChanged" | "topologyOpening" | "topologyClosed" | "topologyDescriptionChanged" | "connectionPoolCreated" | "connectionPoolClosed" | "connectionPoolCleared" | "connectionPoolReady" | "connectionCreated" | "connectionReady" | "connectionClosed" | "connectionCheckOutStarted" | "connectionCheckOutFailed" | "connectionCheckedOut" | "connectionCheckedIn" | "commandStarted" | "commandSucceeded" | "commandFailed" | "serverHeartbeatStarted" | "serverHeartbeatSucceeded" | "serverHeartbeatFailed"

    Parameters

    • event: string | symbol | EventKey

    Returns MongoClientEvents[EventKey][]

  • Type Parameters

    • EventKey extends "error" | "timeout" | "close" | "open" | "serverOpening" | "serverClosed" | "serverDescriptionChanged" | "topologyOpening" | "topologyClosed" | "topologyDescriptionChanged" | "connectionPoolCreated" | "connectionPoolClosed" | "connectionPoolCleared" | "connectionPoolReady" | "connectionCreated" | "connectionReady" | "connectionClosed" | "connectionCheckOutStarted" | "connectionCheckOutFailed" | "connectionCheckedOut" | "connectionCheckedIn" | "commandStarted" | "commandSucceeded" | "commandFailed" | "serverHeartbeatStarted" | "serverHeartbeatSucceeded" | "serverHeartbeatFailed"

    Parameters

    Returns MongoClient

  • Parameters

    • event: CommonEvents
    • listener: ((eventName, listener) => void)
        • (eventName, listener): void
        • Parameters

          Returns void

    Returns MongoClient

  • Parameters

    Returns MongoClient

  • Type Parameters

    • EventKey extends "error" | "timeout" | "close" | "open" | "serverOpening" | "serverClosed" | "serverDescriptionChanged" | "topologyOpening" | "topologyClosed" | "topologyDescriptionChanged" | "connectionPoolCreated" | "connectionPoolClosed" | "connectionPoolCleared" | "connectionPoolReady" | "connectionCreated" | "connectionReady" | "connectionClosed" | "connectionCheckOutStarted" | "connectionCheckOutFailed" | "connectionCheckedOut" | "connectionCheckedIn" | "commandStarted" | "commandSucceeded" | "commandFailed" | "serverHeartbeatStarted" | "serverHeartbeatSucceeded" | "serverHeartbeatFailed"

    Parameters

    Returns MongoClient

  • Parameters

    • event: CommonEvents
    • listener: ((eventName, listener) => void)
        • (eventName, listener): void
        • Parameters

          Returns void

    Returns MongoClient

  • Parameters

    Returns MongoClient

  • Type Parameters

    • EventKey extends "error" | "timeout" | "close" | "open" | "serverOpening" | "serverClosed" | "serverDescriptionChanged" | "topologyOpening" | "topologyClosed" | "topologyDescriptionChanged" | "connectionPoolCreated" | "connectionPoolClosed" | "connectionPoolCleared" | "connectionPoolReady" | "connectionCreated" | "connectionReady" | "connectionClosed" | "connectionCheckOutStarted" | "connectionCheckOutFailed" | "connectionCheckedOut" | "connectionCheckedIn" | "commandStarted" | "commandSucceeded" | "commandFailed" | "serverHeartbeatStarted" | "serverHeartbeatSucceeded" | "serverHeartbeatFailed"

    Parameters

    Returns MongoClient

  • Parameters

    • event: CommonEvents
    • listener: ((eventName, listener) => void)
        • (eventName, listener): void
        • Parameters

          Returns void

    Returns MongoClient

  • Parameters

    Returns MongoClient

  • Type Parameters

    • EventKey extends "error" | "timeout" | "close" | "open" | "serverOpening" | "serverClosed" | "serverDescriptionChanged" | "topologyOpening" | "topologyClosed" | "topologyDescriptionChanged" | "connectionPoolCreated" | "connectionPoolClosed" | "connectionPoolCleared" | "connectionPoolReady" | "connectionCreated" | "connectionReady" | "connectionClosed" | "connectionCheckOutStarted" | "connectionCheckOutFailed" | "connectionCheckedOut" | "connectionCheckedIn" | "commandStarted" | "commandSucceeded" | "commandFailed" | "serverHeartbeatStarted" | "serverHeartbeatSucceeded" | "serverHeartbeatFailed"

    Parameters

    • event: string | symbol | EventKey

    Returns MongoClientEvents[EventKey][]

  • Type Parameters

    • EventKey extends "error" | "timeout" | "close" | "open" | "serverOpening" | "serverClosed" | "serverDescriptionChanged" | "topologyOpening" | "topologyClosed" | "topologyDescriptionChanged" | "connectionPoolCreated" | "connectionPoolClosed" | "connectionPoolCleared" | "connectionPoolReady" | "connectionCreated" | "connectionReady" | "connectionClosed" | "connectionCheckOutStarted" | "connectionCheckOutFailed" | "connectionCheckedOut" | "connectionCheckedIn" | "commandStarted" | "commandSucceeded" | "commandFailed" | "serverHeartbeatStarted" | "serverHeartbeatSucceeded" | "serverHeartbeatFailed"

    Parameters

    • Optional event: string | symbol | EventKey

    Returns MongoClient

  • Create a new Change Stream, watching for new changes (insertions, updates, replacements, deletions, and invalidations) in this cluster. Will ignore all changes to system collections, as well as the local, admin, and config databases.

    Type Parameters

    Parameters

    • pipeline: Document[] = []

      An array of pipeline stages through which to pass change stream documents. This allows for filtering (using $match) and manipulating the change stream documents.

    • options: ChangeStreamOptions = {}

      Optional settings for the command

    Returns ChangeStream<TSchema, TChange>

    Remarks

    watch() accepts two generic arguments for distinct use cases:

    • The first is to provide the schema that may be defined for all the data within the current cluster
    • The second is to override the shape of the change stream document entirely, if it is not provided the type will default to ChangeStreamDocument of the first argument
  • Runs a given operation with an implicitly created session. The lifetime of the session will be handled without the need for user interaction.

    NOTE: presently the operation MUST return a Promise (either explicit or implicitly as an async function)

    Parameters

    Returns Promise<void>

  • Parameters

    Returns Promise<void>

  • Returns a copy of the array of listeners for the event named eventName.

    For EventEmitters this behaves exactly the same as calling .listeners on the emitter.

    For EventTargets this is the only way to get the event listeners for the event target. This is useful for debugging and diagnostic purposes.

    import { getEventListeners, EventEmitter } from 'node:events';

    {
    const ee = new EventEmitter();
    const listener = () => console.log('Events are fun');
    ee.on('foo', listener);
    console.log(getEventListeners(ee, 'foo')); // [ [Function: listener] ]
    }
    {
    const et = new EventTarget();
    const listener = () => console.log('Events are fun');
    et.addEventListener('foo', listener);
    console.log(getEventListeners(et, 'foo')); // [ [Function: listener] ]
    }

    Parameters

    • emitter: EventEmitter | _DOMEventTarget
    • name: string | symbol

    Returns Function[]

    Since

    v15.2.0, v14.17.0

  • A class method that returns the number of listeners for the given eventNameregistered on the given emitter.

    import { EventEmitter, listenerCount } from 'node:events';

    const myEmitter = new EventEmitter();
    myEmitter.on('event', () => {});
    myEmitter.on('event', () => {});
    console.log(listenerCount(myEmitter, 'event'));
    // Prints: 2

    Parameters

    • emitter: EventEmitter

      The emitter to query

    • eventName: string | symbol

      The event name

    Returns number

    Since

    v0.9.12

    Deprecated

    Since v3.2.0 - Use listenerCount instead.

  • import { on, EventEmitter } from 'node:events';
    import process from 'node:process';

    const ee = new EventEmitter();

    // Emit later on
    process.nextTick(() => {
    ee.emit('foo', 'bar');
    ee.emit('foo', 42);
    });

    for await (const event of on(ee, 'foo')) {
    // The execution of this inner block is synchronous and it
    // processes one event at a time (even with await). Do not use
    // if concurrent execution is required.
    console.log(event); // prints ['bar'] [42]
    }
    // Unreachable here

    Returns an AsyncIterator that iterates eventName events. It will throw if the EventEmitter emits 'error'. It removes all listeners when exiting the loop. The value returned by each iteration is an array composed of the emitted event arguments.

    An AbortSignal can be used to cancel waiting on events:

    import { on, EventEmitter } from 'node:events';
    import process from 'node:process';

    const ac = new AbortController();

    (async () => {
    const ee = new EventEmitter();

    // Emit later on
    process.nextTick(() => {
    ee.emit('foo', 'bar');
    ee.emit('foo', 42);
    });

    for await (const event of on(ee, 'foo', { signal: ac.signal })) {
    // The execution of this inner block is synchronous and it
    // processes one event at a time (even with await). Do not use
    // if concurrent execution is required.
    console.log(event); // prints ['bar'] [42]
    }
    // Unreachable here
    })();

    process.nextTick(() => ac.abort());

    Parameters

    • emitter: EventEmitter
    • eventName: string

      The name of the event being listened for

    • Optional options: StaticEventEmitterOptions

    Returns AsyncIterableIterator<any>

    that iterates eventName events emitted by the emitter

    Since

    v13.6.0, v12.16.0

  • Creates a Promise that is fulfilled when the EventEmitter emits the given event or that is rejected if the EventEmitter emits 'error' while waiting. The Promise will resolve with an array of all the arguments emitted to the given event.

    This method is intentionally generic and works with the web platform EventTarget interface, which has no special'error' event semantics and does not listen to the 'error' event.

    import { once, EventEmitter } from 'node:events';
    import process from 'node:process';

    const ee = new EventEmitter();

    process.nextTick(() => {
    ee.emit('myevent', 42);
    });

    const [value] = await once(ee, 'myevent');
    console.log(value);

    const err = new Error('kaboom');
    process.nextTick(() => {
    ee.emit('error', err);
    });

    try {
    await once(ee, 'myevent');
    } catch (err) {
    console.error('error happened', err);
    }

    The special handling of the 'error' event is only used when events.once()is used to wait for another event. If events.once() is used to wait for the 'error' event itself, then it is treated as any other kind of event without special handling:

    import { EventEmitter, once } from 'node:events';

    const ee = new EventEmitter();

    once(ee, 'error')
    .then(([err]) => console.log('ok', err.message))
    .catch((err) => console.error('error', err.message));

    ee.emit('error', new Error('boom'));

    // Prints: ok boom

    An AbortSignal can be used to cancel waiting for the event:

    import { EventEmitter, once } from 'node:events';

    const ee = new EventEmitter();
    const ac = new AbortController();

    async function foo(emitter, event, signal) {
    try {
    await once(emitter, event, { signal });
    console.log('event emitted!');
    } catch (error) {
    if (error.name === 'AbortError') {
    console.error('Waiting for the event was canceled!');
    } else {
    console.error('There was an error', error.message);
    }
    }
    }

    foo(ee, 'foo', ac.signal);
    ac.abort(); // Abort waiting for the event
    ee.emit('foo'); // Prints: Waiting for the event was canceled!

    Parameters

    • emitter: _NodeEventTarget
    • eventName: string | symbol
    • Optional options: StaticEventEmitterOptions

    Returns Promise<any[]>

    Since

    v11.13.0, v10.16.0

  • Parameters

    • emitter: _DOMEventTarget
    • eventName: string
    • Optional options: StaticEventEmitterOptions

    Returns Promise<any[]>

  • import { setMaxListeners, EventEmitter } from 'node:events';

    const target = new EventTarget();
    const emitter = new EventEmitter();

    setMaxListeners(5, target, emitter);

    Parameters

    • Optional n: number

      A non-negative number. The maximum number of listeners per EventTarget event.

    • Rest ...eventTargets: (EventEmitter | _DOMEventTarget)[]

    Returns void

    Since

    v15.4.0

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