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Class MongoClient

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

remarks

The programmatically provided options take precedent over the URI options.

example
// Connect using a MongoClient instance
const MongoClient = require('mongodb').MongoClient;
const test = require('assert');
// Connection url
const url = 'mongodb://localhost:27017';
// Database Name
const dbName = 'test';
// Connect using MongoClient
const mongoClient = new MongoClient(url);
mongoClient.connect(function(err, client) {
const db = client.db(dbName);
client.close();
});
example
// Connect using the MongoClient.connect static method
const MongoClient = require('mongodb').MongoClient;
const test = require('assert');
// Connection url
const url = 'mongodb://localhost:27017';
// Database Name
const dbName = 'test';
// Connect using MongoClient
MongoClient.connect(url, function(err, client) {
const db = client.db(dbName);
client.close();
});

Hierarchy

Index

Constructors

constructor

Properties

[kOptions]

[kOptions]: MongoOptions

The consolidate, parsed, transformed and merged options.

s

Optional topology

topology?: Topology

Static Readonly captureRejectionSymbol

captureRejectionSymbol: typeof captureRejectionSymbol

Static captureRejections

captureRejections: boolean

Sets or gets the default captureRejection value for all emitters.

Static defaultMaxListeners

defaultMaxListeners: number

Static Readonly errorMonitor

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

autoEncrypter

bsonOptions

logger

monitorCommands

  • get monitorCommands(): boolean
  • set monitorCommands(value: boolean): void

options

readConcern

readPreference

serverApi

  • get serverApi(): Readonly<undefined | ServerApi>

writeConcern

Methods

addListener

close

  • close(): Promise<void>
  • close(callback: Callback<void>): void
  • close(force: boolean): Promise<void>
  • close(force: boolean, callback: Callback<void>): void

connect

db

  • 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

emit

  • emit<EventKey>(event: symbol | EventKey, ...args: Parameters<MongoClientEvents[EventKey]>): boolean
  • Type parameters

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

    Parameters

    Returns boolean

eventNames

  • eventNames(): string[]

getLogger

getMaxListeners

  • getMaxListeners(): number

listenerCount

  • listenerCount<EventKey>(type: string | symbol | EventKey): number
  • Type parameters

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

    Parameters

    • type: string | symbol | EventKey

    Returns number

listeners

  • listeners<EventKey>(event: string | symbol | EventKey): MongoClientEvents[EventKey][]
  • Type parameters

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

    Parameters

    • event: string | symbol | EventKey

    Returns MongoClientEvents[EventKey][]

off

on

once

prependListener

prependOnceListener

rawListeners

  • rawListeners<EventKey>(event: string | symbol | EventKey): MongoClientEvents[EventKey][]
  • Type parameters

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

    Parameters

    • event: string | symbol | EventKey

    Returns MongoClientEvents[EventKey][]

removeAllListeners

  • removeAllListeners<EventKey>(event?: string | symbol | EventKey): MongoClient
  • Type parameters

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

    Parameters

    • Optional event: string | symbol | EventKey

    Returns MongoClient

removeListener

setMaxListeners

startSession

watch

  • 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

    Returns ChangeStream<TSchema>

withSession

  • 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>

Static connect

Static getEventListeners

  • getEventListeners(emitter: DOMEventTarget | EventEmitter, name: string | symbol): Function[]
  • 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.

    const { getEventListeners, EventEmitter } = require('events');

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

    v15.2.0

    Parameters

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

    Returns Function[]

Static listenerCount

  • listenerCount(emitter: EventEmitter, eventName: string | symbol): number
  • A class method that returns the number of listeners for the given eventNameregistered on the given emitter.

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

    v0.9.12

    deprecated

    Since v3.2.0 - Use listenerCount instead.

    Parameters

    • emitter: EventEmitter

      The emitter to query

    • eventName: string | symbol

      The event name

    Returns number

Static on

  • on(emitter: EventEmitter, eventName: string, options?: StaticEventEmitterOptions): AsyncIterableIterator<any>
  • ```js const { on, EventEmitter } = require('events');

    (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')) { // 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:

    ```js
    const { on, EventEmitter } = require('events');
    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());
    since

    v13.6.0, v12.16.0

    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

Static once

  • once(emitter: NodeEventTarget, eventName: string | symbol, options?: StaticEventEmitterOptions): Promise<any[]>
  • once(emitter: DOMEventTarget, eventName: string, options?: StaticEventEmitterOptions): Promise<any[]>
  • 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.

    const { once, EventEmitter } = require('events');

    async function run() {
    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.log('error happened', err);
    }
    }

    run();

    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:

    const { EventEmitter, once } = require('events');

    const ee = new EventEmitter();

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

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

    // Prints: ok boom

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

    const { EventEmitter, once } = require('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!
    since

    v11.13.0, v10.16.0

    Parameters

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

    Returns Promise<any[]>

  • Parameters

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

    Returns Promise<any[]>

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