Class ChangeStream<TSchema, TChange>

Creates a new Change Stream instance. Normally created using Collection.watch().

Type Parameters

Hierarchy

Constructors

Properties

namespace: MongoDBNamespace
options: ChangeStreamOptions & {
    writeConcern?: never;
}

Type declaration

  • Optional writeConcern?: never

Remarks

WriteConcern can still be present on the options because we inherit options from the client/db/collection. The key must be present on the options in order to delete it. This allows typescript to delete the key but will not allow a writeConcern to be assigned as a property on options.

streamOptions?: CursorStreamOptions
type: symbol
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

  • get closed(): boolean
  • Is the cursor closed

    Returns boolean

  • get resumeToken(): unknown
  • The cached resume token that is used to resume after the most recently returned change.

    Returns unknown

Methods

  • Returns AsyncGenerator<TChange, void, void>

  • Type Parameters

    • K

    Parameters

    • error: Error
    • event: string | symbol
    • Rest ...args: AnyRest
      Rest

    Returns void

  • Type Parameters

    • EventKey extends "error" | "end" | "response" | "init" | "close" | "change" | "more" | "resumeTokenChanged"

    Parameters

    Returns ChangeStream<TSchema, TChange>

  • Parameters

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

          Returns void

    Returns ChangeStream<TSchema, TChange>

  • Parameters

    Returns ChangeStream<TSchema, TChange>

  • Close the Change Stream

    Returns Promise<void>

  • Type Parameters

    • EventKey extends "error" | "end" | "response" | "init" | "close" | "change" | "more" | "resumeTokenChanged"

    Parameters

    • event: symbol | EventKey
    • Rest ...args: Parameters<ChangeStreamEvents<TSchema, TChange>[EventKey]>
      Rest

    Returns boolean

  • Returns string[]

  • Returns number

  • Check if there is any document still available in the Change Stream

    Returns Promise<boolean>

  • Type Parameters

    • EventKey extends "error" | "end" | "response" | "init" | "close" | "change" | "more" | "resumeTokenChanged"

    Parameters

    • type: string | symbol | EventKey

    Returns number

  • Type Parameters

    • EventKey extends "error" | "end" | "response" | "init" | "close" | "change" | "more" | "resumeTokenChanged"

    Parameters

    • event: string | symbol | EventKey

    Returns ChangeStreamEvents<TSchema, TChange>[EventKey][]

  • Get the next available document from the Change Stream.

    Returns Promise<TChange>

  • Type Parameters

    • EventKey extends "error" | "end" | "response" | "init" | "close" | "change" | "more" | "resumeTokenChanged"

    Parameters

    Returns ChangeStream<TSchema, TChange>

  • Parameters

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

          Returns void

    Returns ChangeStream<TSchema, TChange>

  • Parameters

    Returns ChangeStream<TSchema, TChange>

  • Type Parameters

    • EventKey extends "error" | "end" | "response" | "init" | "close" | "change" | "more" | "resumeTokenChanged"

    Parameters

    Returns ChangeStream<TSchema, TChange>

  • Parameters

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

          Returns void

    Returns ChangeStream<TSchema, TChange>

  • Parameters

    Returns ChangeStream<TSchema, TChange>

  • Type Parameters

    • EventKey extends "error" | "end" | "response" | "init" | "close" | "change" | "more" | "resumeTokenChanged"

    Parameters

    Returns ChangeStream<TSchema, TChange>

  • Parameters

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

          Returns void

    Returns ChangeStream<TSchema, TChange>

  • Parameters

    Returns ChangeStream<TSchema, TChange>

  • Type Parameters

    • EventKey extends "error" | "end" | "response" | "init" | "close" | "change" | "more" | "resumeTokenChanged"

    Parameters

    Returns ChangeStream<TSchema, TChange>

  • Parameters

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

          Returns void

    Returns ChangeStream<TSchema, TChange>

  • Parameters

    Returns ChangeStream<TSchema, TChange>

  • Type Parameters

    • EventKey extends "error" | "end" | "response" | "init" | "close" | "change" | "more" | "resumeTokenChanged"

    Parameters

    • event: string | symbol | EventKey

    Returns ChangeStreamEvents<TSchema, TChange>[EventKey][]

  • Type Parameters

    • EventKey extends "error" | "end" | "response" | "init" | "close" | "change" | "more" | "resumeTokenChanged"

    Parameters

    • Optional event: string | symbol | EventKey
      Optional

    Returns ChangeStream<TSchema, TChange>

  • Type Parameters

    • EventKey extends "error" | "end" | "response" | "init" | "close" | "change" | "more" | "resumeTokenChanged"

    Parameters

    Returns ChangeStream<TSchema, TChange>

  • Parameters

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

          Returns void

    Returns ChangeStream<TSchema, TChange>

  • Parameters

    Returns ChangeStream<TSchema, TChange>

  • Return a modified Readable stream including a possible transform method.

    NOTE: When using a Stream to process change stream events, the stream will NOT automatically resume in the case a resumable error is encountered.

    Parameters

    Returns Readable & AsyncIterable<TChange>

    Throws

    MongoChangeStreamError if the underlying cursor or the change stream is closed

  • Try to get the next available document from the Change Stream's cursor or null if an empty batch is returned

    Returns Promise<TChange>

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

    Parameters

    • emitter: EventEmitter<DefaultEventMap> | DOMEventTarget
    • name: string | symbol

    Returns Function[]

    Since

    v15.2.0

  • 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<DefaultEventMap>

      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';

    (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:

    import { on, EventEmitter } from 'node: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());

    Parameters

    • emitter: EventEmitter<DefaultEventMap>
    • eventName: string

      The name of the event being listened for

    • Optional options: StaticEventEmitterOptions
      Optional

    Returns AsyncIterator<any, any, 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';

    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:

    import { EventEmitter, once } from 'node: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:

    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
      Optional

    Returns Promise<any[]>

    Since

    v11.13.0, v10.16.0

  • Parameters

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

    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.

      Optional
    • Rest ...eventTargets: (EventEmitter<DefaultEventMap> | DOMEventTarget)[]

      Zero or more {EventTarget} or {EventEmitter} instances. If none are specified, n is set as the default max for all newly created {EventTarget} and {EventEmitter} objects.

      Rest

    Returns void

    Since

    v15.4.0

Events

CHANGE: "change"

Fired for each new matching change in the specified namespace. Attaching a change event listener to a Change Stream will switch the stream into flowing mode. Data will then be passed as soon as it is available.

CLOSE: "close"
END: "end"
ERROR: "error"
INIT: "init"
MORE: "more"
RESPONSE: "response"
RESUME_TOKEN_CHANGED: "resumeTokenChanged"

Emitted each time the change stream stores a new resume token.

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