LiveEvent class

new LiveEvent(props: IDataObjectProps<{ Events: ILiveEventEvents<TEvent> }>)

Parameters

boolean disposed

Property Value

The objects fluid type factory.

static factory: DataObjectFactory<LiveEvent<any>, DataObjectTypes>

Property Value

Handle to a data store

IFluidHandle<this> handle

Property Value

string id

Property Value

IFluidHandle<this> IFluidHandle

Property Value

this IFluidLoadable

Property Value

this IFluidRouter

Property Value

The initialization status of the data object.

LiveDataObjectInitializeState initializeState

Property Value

Flag that indicates whether initialization has succeeded or not.

boolean isInitialized

Property Value

The objects fluid type/name.

static TypeName: "@microsoft/live-share:LiveEvent" = "@microsoft/live-share:LiveEvent"

Property Value

addListener: TypedEventTransform<LiveEvent<TEvent>, ILiveEventEvents<TEvent> & IEvent>

Property Value

Inherited From LiveDataObject.addListener

Value: boolean

Change the default captureRejections option on all new EventEmitter objects.

static captureRejections: boolean

Property Value

Inherited From LiveDataObject.captureRejections

Value: Symbol.for('nodejs.rejection')

See how to write a custom rejection handler.

static captureRejectionSymbol: typeof captureRejectionSymbol

Property Value

Inherited From LiveDataObject.captureRejectionSymbol

By default, a maximum of 10 listeners can be registered for any single event. This limit can be changed for individual EventEmitter instances using the emitter.setMaxListeners(n) method. To change the default for allEventEmitter instances, the events.defaultMaxListeners property can be used. If this value is not a positive number, a RangeError is thrown.

Take caution when setting the events.defaultMaxListeners because the change affects all EventEmitter instances, including those created before the change is made. However, calling emitter.setMaxListeners(n) still has precedence over events.defaultMaxListeners.

This is not a hard limit. The EventEmitter instance will allow more listeners to be added but will output a trace warning to stderr indicating that a "possible EventEmitter memory leak" has been detected. For any single EventEmitter, the emitter.getMaxListeners() and emitter.setMaxListeners() methods can be used to temporarily avoid this warning:

import { EventEmitter } from 'node:events';
const emitter = new EventEmitter();
emitter.setMaxListeners(emitter.getMaxListeners() + 1);
emitter.once('event', () => {
  // do stuff
  emitter.setMaxListeners(Math.max(emitter.getMaxListeners() - 1, 0));
});

The --trace-warnings command-line flag can be used to display the stack trace for such warnings.

The emitted warning can be inspected with process.on('warning') and will have the additional emitter, type, and count properties, referring to the event emitter instance, the event's name and the number of attached listeners, respectively. Its name property is set to 'MaxListenersExceededWarning'.

static defaultMaxListeners: number

Property Value

Inherited From LiveDataObject.defaultMaxListeners

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.

static errorMonitor: typeof errorMonitor

Property Value

Inherited From LiveDataObject.errorMonitor

off: TypedEventTransform<LiveEvent<TEvent>, ILiveEventEvents<TEvent> & IEvent>

Property Value

Inherited From LiveDataObject.off

on: TypedEventTransform<LiveEvent<TEvent>, ILiveEventEvents<TEvent> & IEvent>

Property Value

Inherited From LiveDataObject.on

once: TypedEventTransform<LiveEvent<TEvent>, ILiveEventEvents<TEvent> & IEvent>

Property Value

Inherited From LiveDataObject.once

prependListener: TypedEventTransform<LiveEvent<TEvent>, ILiveEventEvents<TEvent> & IEvent>

Property Value

Inherited From LiveDataObject.prependListener

prependOnceListener: TypedEventTransform<LiveEvent<TEvent>, ILiveEventEvents<TEvent> & IEvent>

Property Value

Inherited From LiveDataObject.prependOnceListener

removeListener: TypedEventTransform<LiveEvent<TEvent>, ILiveEventEvents<TEvent> & IEvent>

Property Value

Inherited From LiveDataObject.removeListener

Initialize the object to begin sending/receiving events through this DDS.

function initialize(allowedRoles?: UserMeetingRole[]): Promise<void>

Parameters

Returns

a void promise that resolves once complete.

Remarks

You should register received event listeners before calling this function to ensure no incoming events are missed. received events will not be emitted until after this function is called.

Returns true if a received event is newer then the current event.

static function isNewer(current: undefined | IClientTimestamp, received: IClientTimestamp, debouncePeriod?: number): boolean

Parameters

Returns

True if the received event is newer then the current event and should replace the current one.

Remarks

Used when building new Live objects to process state change events. The isNewer() method implements an algorithm that deals with conflicting events that have the same timestamp and older events that should have debounced the current event.

• When the received event has the same timestamp as the current event, each events clientId will be used as a tie breaker. The clientId containing the lower sort order wins any ties.
• Older events are generally ignored unless a debounce period is specified. An older event that should have debounced the current event will be considered newer.

The algorithm employed by isNewer() helps ensure that all clients will eventually reach a consistent state with one other.

Broadcasts an event to all other clients.

function send(evt: TEvent): Promise<ILiveEvent<TEvent>>

Parameters

Returns

A promise with the full event object that was sent, including the timestamp of when the event was sent and the clientId if known. The clientId will be undefined if the client is disconnected at time of delivery.

Remarks

The event will be queued for delivery if the client isn't currently connected.

Listens once to the abort event on the provided signal.

Listening to the abort event on abort signals is unsafe and may lead to resource leaks since another third party with the signal can call e.stopImmediatePropagation(). Unfortunately Node.js cannot change this since it would violate the web standard. Additionally, the original API makes it easy to forget to remove listeners.

This API allows safely using AbortSignals in Node.js APIs by solving these two issues by listening to the event such that stopImmediatePropagation does not prevent the listener from running.

Returns a disposable so that it may be unsubscribed from more easily.

import { addAbortListener } from 'node:events';

function example(signal) {
  let disposable;
  try {
    signal.addEventListener('abort', (e) => e.stopImmediatePropagation());
    disposable = addAbortListener(signal, (e) => {
      // Do something when signal is aborted.
    });
  } finally {
    disposable?.[Symbol.dispose]();
  }
}

static function addAbortListener(signal: AbortSignal, resource: (event: Event) => void): Disposable

Parameters

Returns

Disposable that removes the abort listener.

Inherited From LiveDataObject.addAbortListener

Called when the host container closes and disposes itself

function dispose()

Inherited From LiveDataObject.dispose

Synchronously calls each of the listeners registered for the event named eventName, in the order they were registered, passing the supplied arguments to each.

Returns true if the event had listeners, false otherwise.

import { EventEmitter } from 'node:events';
const myEmitter = new EventEmitter();

// First listener
myEmitter.on('event', function firstListener() {
  console.log('Helloooo! first listener');
});
// Second listener
myEmitter.on('event', function secondListener(arg1, arg2) {
  console.log(`event with parameters ${arg1}, ${arg2} in second listener`);
});
// Third listener
myEmitter.on('event', function thirdListener(...args) {
  const parameters = args.join(', ');
  console.log(`event with parameters ${parameters} in third listener`);
});

console.log(myEmitter.listeners('event'));

myEmitter.emit('event', 1, 2, 3, 4, 5);

// Prints:
// [
//   [Function: firstListener],
//   [Function: secondListener],
//   [Function: thirdListener]
// ]
// Helloooo! first listener
// event with parameters 1, 2 in second listener
// event with parameters 1, 2, 3, 4, 5 in third listener

function emit<K>(eventName: string | symbol, args: AnyRest): boolean

Parameters

Returns

Inherited From LiveDataObject.emit

Returns an array listing the events for which the emitter has registered listeners. The values in the array are strings or Symbols.

import { EventEmitter } from 'node:events';

const myEE = new EventEmitter();
myEE.on('foo', () => {});
myEE.on('bar', () => {});

const sym = Symbol('symbol');
myEE.on(sym, () => {});

console.log(myEE.eventNames());
// Prints: [ 'foo', 'bar', Symbol(symbol) ]

function eventNames(): (string | symbol)[]

Returns

Inherited From LiveDataObject.eventNames

Call this API to ensure PureDataObject is fully initialized. Initialization happens on demand, only on as-needed bases. In most cases you should allow factory/object to decide when to finish initialization. But if you are supplying your own implementation of DataStoreRuntime factory and overriding some methods and need a fully initialized object, then you can call this API to ensure object is fully initialized.

function finishInitialization(existing: boolean): Promise<void>

Parameters

Returns

Inherited From LiveDataObject.finishInitialization

Get the client info for a given clientId

function getClientInfo(clientId: string): Promise<undefined | IClientInfo>

Parameters

Returns

IClientInfo object if the user is known, otherwise it will return undefined

Inherited From LiveDataObject.getClientInfo

static function getDataObject(runtime: IFluidDataStoreRuntime): Promise<PureDataObject<DataObjectTypes>>

Parameters

Returns

Inherited From LiveDataObject.getDataObject

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] ]
}

static function getEventListeners(emitter: EventEmitter<DefaultEventMap> | EventTarget, name: string | symbol): Function[]

Parameters

Returns

Inherited From LiveDataObject.getEventListeners

Retrieve Fluid object using the handle get

function getFluidObjectFromDirectory<T>(key: string, directory: IDirectory, getObjectFromDirectory?: (id: string, directory: IDirectory) => undefined | IFluidHandle<FluidObject<unknown> & IFluidLoadable>): Promise<undefined | T>

Parameters

Returns

Inherited From LiveDataObject.getFluidObjectFromDirectory

Returns the current max listener value for the EventEmitter which is either set by emitter.setMaxListeners(n) or defaults to defaultMaxListeners.

function getMaxListeners(): number

Returns

Inherited From LiveDataObject.getMaxListeners

Returns the currently set max amount of listeners.

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

For EventTargets this is the only way to get the max event listeners for the event target. If the number of event handlers on a single EventTarget exceeds the max set, the EventTarget will print a warning.

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

{
  const ee = new EventEmitter();
  console.log(getMaxListeners(ee)); // 10
  setMaxListeners(11, ee);
  console.log(getMaxListeners(ee)); // 11
}
{
  const et = new EventTarget();
  console.log(getMaxListeners(et)); // 10
  setMaxListeners(11, et);
  console.log(getMaxListeners(et)); // 11
}

static function getMaxListeners(emitter: EventEmitter<DefaultEventMap> | EventTarget): number

Parameters

Returns

Inherited From LiveDataObject.getMaxListeners

Initializes internal objects and calls initialization overrides. Caller is responsible for ensuring this is only invoked once.

function initializeInternal(existing: boolean): Promise<void>

Parameters

Returns

Inherited From LiveDataObject.initializeInternal

A class method that returns the number of listeners for the given eventName registered 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

static function listenerCount(emitter: EventEmitter<DefaultEventMap>, eventName: string | symbol): number

Parameters

Returns

Inherited From LiveDataObject.listenerCount

Returns the number of listeners listening for the event named eventName. If listener is provided, it will return how many times the listener is found in the list of the listeners of the event.

function listenerCount<K>(eventName: string | symbol, listener?: Function): number

Parameters

Returns

Inherited From LiveDataObject.listenerCount

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

server.on('connection', (stream) => {
  console.log('someone connected!');
});
console.log(util.inspect(server.listeners('connection')));
// Prints: [ [Function] ]

function listeners<K>(eventName: string | symbol): Function[]

Parameters

Returns

Inherited From LiveDataObject.listeners

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());

Use the close option to specify an array of event names that will end the iteration:

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);
  ee.emit('close');
});

for await (const event of on(ee, 'foo', { close: ['close'] })) {
  console.log(event); // prints ['bar'] [42]
}
// the loop will exit after 'close' is emitted
console.log('done'); // prints 'done'

static function on(emitter: EventEmitter<DefaultEventMap>, eventName: string | symbol, options?: StaticEventEmitterIteratorOptions): AsyncIterator<any[], any, any>

Parameters

Returns

An AsyncIterator that iterates eventName events emitted by the emitter

Inherited From LiveDataObject.on

static function on(emitter: EventTarget, eventName: string, options?: StaticEventEmitterIteratorOptions): AsyncIterator<any[], any, any>

Parameters

Returns

Inherited From LiveDataObject.on

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!

static function once(emitter: EventEmitter<DefaultEventMap>, eventName: string | symbol, options?: StaticEventEmitterOptions): Promise<any[]>

Parameters

Returns

Inherited From LiveDataObject.once

static function once(emitter: EventTarget, eventName: string, options?: StaticEventEmitterOptions): Promise<any[]>

Parameters

Returns

Inherited From LiveDataObject.once

Returns a copy of the array of listeners for the event named eventName, including any wrappers (such as those created by .once()).

import { EventEmitter } from 'node:events';
const emitter = new EventEmitter();
emitter.once('log', () => console.log('log once'));

// Returns a new Array with a function `onceWrapper` which has a property
// `listener` which contains the original listener bound above
const listeners = emitter.rawListeners('log');
const logFnWrapper = listeners[0];

// Logs "log once" to the console and does not unbind the `once` event
logFnWrapper.listener();

// Logs "log once" to the console and removes the listener
logFnWrapper();

emitter.on('log', () => console.log('log persistently'));
// Will return a new Array with a single function bound by `.on()` above
const newListeners = emitter.rawListeners('log');

// Logs "log persistently" twice
newListeners[0]();
emitter.emit('log');

function rawListeners<K>(eventName: string | symbol): Function[]

Parameters

Returns

Inherited From LiveDataObject.rawListeners

Removes all listeners, or those of the specified eventName.

It is bad practice to remove listeners added elsewhere in the code, particularly when the EventEmitter instance was created by some other component or module (e.g. sockets or file streams).

Returns a reference to the EventEmitter, so that calls can be chained.

function removeAllListeners(eventName?: string | symbol): LiveEvent<TEvent>

Parameters

Returns

Inherited From LiveDataObject.removeAllListeners

{@inheritDoc PureDataObject.request}

function request(request: IRequest): Promise<IResponse>

Parameters

Returns

Inherited From LiveDataObject.request

By default EventEmitters will print a warning if more than 10 listeners are added for a particular event. This is a useful default that helps finding memory leaks. The emitter.setMaxListeners() method allows the limit to be modified for this specific EventEmitter instance. The value can be set to Infinity (or 0) to indicate an unlimited number of listeners.

Returns a reference to the EventEmitter, so that calls can be chained.

function setMaxListeners(n: number): LiveEvent<TEvent>

Parameters

Returns

Inherited From LiveDataObject.setMaxListeners

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

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

setMaxListeners(5, target, emitter);

static function setMaxListeners(n?: number, eventTargets: (EventEmitter<DefaultEventMap> | EventTarget)[])

Parameters

Inherited From LiveDataObject.setMaxListeners

function [captureRejectionSymbol]<K>(error: Error, event: string | symbol, args: AnyRest)

Parameters

Inherited From LiveDataObject.[captureRejectionSymbol]