Class Client

Client for interacting with rippled servers.

Hierarchy

Constructor

Abstraction

getBalances: ((this: Client, address: string, options?: { ledger_hash?: string; ledger_index?: LedgerIndex; limit?: number; peer?: string }) => Promise<{ currency: string; issuer?: string; value: string }[]>) = getBalances

Type declaration

    • (this: Client, address: string, options?: { ledger_hash?: string; ledger_index?: LedgerIndex; limit?: number; peer?: string }): Promise<{ currency: string; issuer?: string; value: string }[]>
    • Get XRP/non-XRP balances for an account.

      Returns

      An array of XRP/non-XRP balances for the given account.

      Parameters

      • this: Client

        Client.

      • address: string

        Address of the account to retrieve balances for.

      • options: { ledger_hash?: string; ledger_index?: LedgerIndex; limit?: number; peer?: string } = {}

        Allows the client to specify a ledger_hash, ledger_index, filter by peer, and/or limit number of balances.

        • Optional ledger_hash?: string

          Retrieve the account balances at the ledger with a given ledger_hash.

        • Optional ledger_index?: LedgerIndex

          Retrieve the account balances at a given ledger_index.

        • Optional limit?: number

          Limit number of balances to return.

        • Optional peer?: string

          Filter balances by peer.

      Returns Promise<{ currency: string; issuer?: string; value: string }[]>

getLedgerIndex: ((this: Client) => Promise<number>) = getLedgerIndex

Type declaration

    • (this: Client): Promise<number>
    • Returns the index of the most recently validated ledger.

      Returns

      The most recently validated ledger index.

      Parameters

      • this: Client

        The Client used to connect to the ledger.

      Returns Promise<number>

getOrderbook: ((this: Client, takerPays: TakerAmount, takerGets: TakerAmount, options?: { ledger_hash?: string; ledger_index?: LedgerIndex; limit?: number; taker?: string }) => Promise<{ buy: BookOffer[]; sell: BookOffer[] }>) = getOrderbook

Type declaration

    • (this: Client, takerPays: TakerAmount, takerGets: TakerAmount, options?: { ledger_hash?: string; ledger_index?: LedgerIndex; limit?: number; taker?: string }): Promise<{ buy: BookOffer[]; sell: BookOffer[] }>
    • Fetch orderbook (buy/sell orders) between two accounts.

      Returns

      An object containing buy and sell objects.

      Parameters

      • this: Client

        Client.

      • takerPays: TakerAmount

        Specification of which currency the account taking the offer would pay, as an object with currency and issuer fields.

      • takerGets: TakerAmount

        Specification of which currency the account taking the offer would receive, as an object with currency and issuer fields.

      • options: { ledger_hash?: string; ledger_index?: LedgerIndex; limit?: number; taker?: string } = {}

        Options allowing the client to specify ledger_index, ledger_hash, filter by taker, and/or limit number of orders.

        • Optional ledger_hash?: string

          Retrieve the orderbook at the ledger with a given ledger_hash.

        • Optional ledger_index?: LedgerIndex

          Retrieve the orderbook at a given ledger_index.

        • Optional limit?: number

          Limit number of order books to fetch for each side of the order book. Defaults to 20.

        • Optional taker?: string

          Filter orders by taker.

      Returns Promise<{ buy: BookOffer[]; sell: BookOffer[] }>

getXrpBalance: ((this: Client, address: string, options?: { ledger_hash?: string; ledger_index?: LedgerIndex }) => Promise<string>) = getXrpBalance

Type declaration

    • (this: Client, address: string, options?: { ledger_hash?: string; ledger_index?: LedgerIndex }): Promise<string>
    • Get the XRP balance for an account.

      Example

      const client = new Client(wss://s.altnet.rippletest.net:51233)
      const balance = await client.getXrpBalance('rG1QQv2nh2gr7RCZ1P8YYcBUKCCN633jCn')
      console.log(balance)
      /// '200'

      Returns

      The XRP balance of the account (as a string).

      Parameters

      • this: Client

        Client.

      • address: string

        Address of the account to retrieve XRP balance.

      • options: { ledger_hash?: string; ledger_index?: LedgerIndex } = {}

        Options to include for getting the XRP balance.

        • Optional ledger_hash?: string

          Retrieve the account balances at the ledger with a given ledger_hash.

        • Optional ledger_index?: LedgerIndex

          Retrieve the account balances at a given ledger_index.

      Returns Promise<string>

Core

autofill: (<T>(this: Client, transaction: T, signersCount?: number) => Promise<T>) = autofill

Type declaration

    • <T>(this: Client, transaction: T, signersCount?: number): Promise<T>
    • Autofills fields in a transaction. This will set Sequence, Fee, lastLedgerSequence according to the current state of the server this Client is connected to. It also converts all X-Addresses to classic addresses and flags interfaces into numbers.

      Returns

      The autofilled transaction.

      Type Parameters

      Parameters

      • this: Client

        A client.

      • transaction: T

        A Transaction in JSON format

      • Optional signersCount: number

        The expected number of signers for this transaction. Only used for multisigned transactions.

      Returns Promise<T>

submit: ((this: Client, transaction: string | Transaction, opts?: { autofill?: boolean; failHard?: boolean; wallet?: Wallet }) => Promise<SubmitResponse>) = submit

Type declaration

    • (this: Client, transaction: string | Transaction, opts?: { autofill?: boolean; failHard?: boolean; wallet?: Wallet }): Promise<SubmitResponse>
    • Submits a signed/unsigned transaction. Steps performed on a transaction:

      1. Autofill.
      2. Sign & Encode.
      3. Submit.

      Returns

      A promise that contains SubmitResponse.

      Throws

      RippledError if submit request fails.

      Parameters

      • this: Client

        A Client.

      • transaction: string | Transaction

        A transaction to autofill, sign & encode, and submit.

      • Optional opts: { autofill?: boolean; failHard?: boolean; wallet?: Wallet }

        (Optional) Options used to sign and submit a transaction.

        • Optional autofill?: boolean

          If true, autofill a transaction.

        • Optional failHard?: boolean

          If true, and the transaction fails locally, do not retry or relay the transaction to other servers.

        • Optional wallet?: Wallet

          A wallet to sign a transaction. It must be provided when submitting an unsigned transaction.

      Returns Promise<SubmitResponse>

submitAndWait: ((this: Client, transaction: string | Transaction, opts?: { autofill?: boolean; failHard?: boolean; wallet?: Wallet }) => Promise<TxResponse>) = submitAndWait

Type declaration

    • (this: Client, transaction: string | Transaction, opts?: { autofill?: boolean; failHard?: boolean; wallet?: Wallet }): Promise<TxResponse>
    • Asynchronously submits a transaction and verifies that it has been included in a validated ledger (or has errored/will not be included for some reason). See Reliable Transaction Submission.

      Returns

      A promise that contains TxResponse, that will return when the transaction has been validated.

      Parameters

      • this: Client

        A Client.

      • transaction: string | Transaction

        A transaction to autofill, sign & encode, and submit.

      • Optional opts: { autofill?: boolean; failHard?: boolean; wallet?: Wallet }

        (Optional) Options used to sign and submit a transaction.

        • Optional autofill?: boolean

          If true, autofill a transaction.

        • Optional failHard?: boolean

          If true, and the transaction fails locally, do not retry or relay the transaction to other servers.

        • Optional wallet?: Wallet

          A wallet to sign a transaction. It must be provided when submitting an unsigned transaction.

      Returns Promise<TxResponse>

Faucet

fundWallet: ((this: Client, wallet?: null | Wallet, options?: { faucetHost?: string }) => Promise<{ balance: number; wallet: Wallet }>) = fundWallet

Type declaration

    • (this: Client, wallet?: null | Wallet, options?: { faucetHost?: string }): Promise<{ balance: number; wallet: Wallet }>
    • Generates a random wallet with some amount of XRP (usually 1000 XRP).

      Example

      const api = new xrpl.Client("wss://s.altnet.rippletest.net:51233")
      await api.connect()
      const { wallet, balance } = await api.fundWallet()

      Returns

      A Wallet on the Testnet or Devnet that contains some amount of XRP, and that wallet's balance in XRP.

      Throws

      When either Client isn't connected or unable to fund wallet address.

      Parameters

      • this: Client

        Client.

      • Optional wallet: null | Wallet

        An existing XRPL Wallet to fund. If undefined or null, a new Wallet will be created.

      • Optional options: { faucetHost?: string }

        See below.

        • Optional faucetHost?: string

          A custom host for a faucet server. On devnet and testnet, fundWallet will attempt to determine the correct server automatically. In other environments, or if you would like to customize the faucet host in devnet or testnet, you should provide the host using this option.

      Returns Promise<{ balance: number; wallet: Wallet }>

Fee

feeCushion: number

Factor to multiply estimated fee by to provide a cushion in case the required fee rises during submission of a transaction. Defaults to 1.2.

maxFeeXRP: string

Maximum transaction cost to allow, in decimal XRP. Must be a string-encoded number. Defaults to '2'.

Network

  • get url(): string
  • Get the url that the client is connected to.

    Returns

    The URL of the server this client is connected to.

    Returns string

  • Tells the Client instance to connect to its rippled server.

    Returns

    A promise that resolves with a void value when a connection is established.

    Returns Promise<void>

  • Tells the Client instance to disconnect from it's rippled server.

    Returns

    A promise that resolves with a void value when a connection is destroyed.

    Returns Promise<void>

  • Checks if the Client instance is connected to its rippled server.

    Returns

    Whether the client instance is connected.

    Returns boolean

  • Event handler for subscription streams.

    Example

    const api = new Client('wss://s.altnet.rippletest.net:51233')

    api.on('transactions', (tx: TransactionStream) => {
    console.log("Received Transaction")
    console.log(tx)
    })

    await api.connect()
    const response = await api.request({
    command: 'subscribe',
    streams: ['transactions_proposed']
    })

    Parameters

    • event: "connected"
    • listener: (() => void)
        • (): void
        • Returns void

    Returns Client

  • Event handler for subscription streams.

    Returns

    This, because it inherits from EventEmitter.

    Parameters

    • event: "disconnected"
    • listener: ((code: number) => void)

      Function to run on event.

        • (code: number): void
        • Parameters

          • code: number

          Returns void

    Returns Client

  • Event handler for subscription streams.

    Returns

    This, because it inherits from EventEmitter.

    Parameters

    Returns Client

  • Event handler for subscription streams.

    Returns

    This, because it inherits from EventEmitter.

    Parameters

    Returns Client

  • Event handler for subscription streams.

    Returns

    This, because it inherits from EventEmitter.

    Parameters

    Returns Client

  • Event handler for subscription streams.

    Returns

    This, because it inherits from EventEmitter.

    Parameters

    Returns Client

  • Event handler for subscription streams.

    Returns

    This, because it inherits from EventEmitter.

    Parameters

    Returns Client

  • Event handler for subscription streams.

    Returns

    This, because it inherits from EventEmitter.

    Parameters

    Returns Client

  • Event handler for subscription streams.

    Returns

    This, because it inherits from EventEmitter.

    Parameters

    • event: "error"
    • listener: ((...err: any[]) => void)

      Function to run on event.

        • (...err: any[]): void
        • Parameters

          • Rest ...err: any[]

          Returns void

    Returns Client

  • Parameters

    Returns Promise<AccountChannelsResponse[]>

  • Makes multiple paged requests to the client to return a given number of resources. Multiple paged requests will be made until the limit number of resources is reached (if no limit is provided, a single request will be made).

    If the command is unknown, an additional collect property is required to know which response key contains the array of resources.

    NOTE: This command is used by existing methods and is not recommended for general use. Instead, use rippled's built-in pagination and make multiple requests as needed.

    Returns

    The array of all responses.

    Throws

    ValidationError if there is no collection key (either from a known command or for the unknown command).

    Parameters

    Returns Promise<AccountLinesResponse[]>

  • Makes multiple paged requests to the client to return a given number of resources. Multiple paged requests will be made until the limit number of resources is reached (if no limit is provided, a single request will be made).

    If the command is unknown, an additional collect property is required to know which response key contains the array of resources.

    NOTE: This command is used by existing methods and is not recommended for general use. Instead, use rippled's built-in pagination and make multiple requests as needed.

    Returns

    The array of all responses.

    Throws

    ValidationError if there is no collection key (either from a known command or for the unknown command).

    Parameters

    Returns Promise<AccountObjectsResponse[]>

  • Makes multiple paged requests to the client to return a given number of resources. Multiple paged requests will be made until the limit number of resources is reached (if no limit is provided, a single request will be made).

    If the command is unknown, an additional collect property is required to know which response key contains the array of resources.

    NOTE: This command is used by existing methods and is not recommended for general use. Instead, use rippled's built-in pagination and make multiple requests as needed.

    Returns

    The array of all responses.

    Throws

    ValidationError if there is no collection key (either from a known command or for the unknown command).

    Parameters

    Returns Promise<AccountOffersResponse[]>

  • Makes multiple paged requests to the client to return a given number of resources. Multiple paged requests will be made until the limit number of resources is reached (if no limit is provided, a single request will be made).

    If the command is unknown, an additional collect property is required to know which response key contains the array of resources.

    NOTE: This command is used by existing methods and is not recommended for general use. Instead, use rippled's built-in pagination and make multiple requests as needed.

    Returns

    The array of all responses.

    Throws

    ValidationError if there is no collection key (either from a known command or for the unknown command).

    Parameters

    Returns Promise<AccountTxResponse[]>

  • Makes multiple paged requests to the client to return a given number of resources. Multiple paged requests will be made until the limit number of resources is reached (if no limit is provided, a single request will be made).

    If the command is unknown, an additional collect property is required to know which response key contains the array of resources.

    NOTE: This command is used by existing methods and is not recommended for general use. Instead, use rippled's built-in pagination and make multiple requests as needed.

    Returns

    The array of all responses.

    Throws

    ValidationError if there is no collection key (either from a known command or for the unknown command).

    Parameters

    Returns Promise<BookOffersResponse[]>

  • Makes multiple paged requests to the client to return a given number of resources. Multiple paged requests will be made until the limit number of resources is reached (if no limit is provided, a single request will be made).

    If the command is unknown, an additional collect property is required to know which response key contains the array of resources.

    NOTE: This command is used by existing methods and is not recommended for general use. Instead, use rippled's built-in pagination and make multiple requests as needed.

    Returns

    The array of all responses.

    Throws

    ValidationError if there is no collection key (either from a known command or for the unknown command).

    Parameters

    Returns Promise<LedgerDataResponse[]>

Other

connection: Connection
prepareTransaction: (<T>(this: Client, transaction: T, signersCount?: number) => Promise<T>) = autofill

Type declaration

    • <T>(this: Client, transaction: T, signersCount?: number): Promise<T>
    • Autofills fields in a transaction. This will set Sequence, Fee, lastLedgerSequence according to the current state of the server this Client is connected to. It also converts all X-Addresses to classic addresses and flags interfaces into numbers.

      Returns

      The autofilled transaction.

      Type Parameters

      Parameters

      • this: Client

        A client.

      • transaction: T

        A Transaction in JSON format

      • Optional signersCount: number

        The expected number of signers for this transaction. Only used for multisigned transactions.

      Returns Promise<T>

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.

  • Alias for emitter.on(eventName, listener).

    Since

    v0.1.26

    Parameters

    • eventName: string | symbol
    • listener: ((...args: any[]) => void)
        • (...args: any[]): void
        • Parameters

          • Rest ...args: any[]

          Returns void

    Returns Client

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

    Returns true if the event had listeners, false otherwise.

    const EventEmitter = require('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

    Since

    v0.1.26

    Parameters

    • eventName: string | symbol
    • Rest ...args: any[]

    Returns boolean

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

    const EventEmitter = require('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) ]

    Since

    v6.0.0

    Returns (string | symbol)[]

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

    Since

    v1.0.0

    Returns number

  • Returns the number of listeners listening to the event named eventName.

    Since

    v3.2.0

    Parameters

    • eventName: string | symbol

      The name of the event being listened for

    Returns number

  • 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] ]

    Since

    v0.1.26

    Parameters

    • eventName: string | symbol

    Returns Function[]

  • Alias for emitter.removeListener().

    Since

    v10.0.0

    Parameters

    • eventName: string | symbol
    • listener: ((...args: any[]) => void)
        • (...args: any[]): void
        • Parameters

          • Rest ...args: any[]

          Returns void

    Returns Client

  • Adds a one-timelistener function for the event named eventName. The next time eventName is triggered, this listener is removed and then invoked.

    server.once('connection', (stream) => {
    console.log('Ah, we have our first user!');
    });

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

    By default, event listeners are invoked in the order they are added. Theemitter.prependOnceListener() method can be used as an alternative to add the event listener to the beginning of the listeners array.

    const myEE = new EventEmitter();
    myEE.once('foo', () => console.log('a'));
    myEE.prependOnceListener('foo', () => console.log('b'));
    myEE.emit('foo');
    // Prints:
    // b
    // a

    Since

    v0.3.0

    Parameters

    • eventName: string | symbol

      The name of the event.

    • listener: ((...args: any[]) => void)

      The callback function

        • (...args: any[]): void
        • Parameters

          • Rest ...args: any[]

          Returns void

    Returns Client

  • Adds the listener function to the beginning of the listeners array for the event named eventName. No checks are made to see if the listener has already been added. Multiple calls passing the same combination of eventNameand listener will result in the listener being added, and called, multiple times.

    server.prependListener('connection', (stream) => {
    console.log('someone connected!');
    });

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

    Since

    v6.0.0

    Parameters

    • eventName: string | symbol

      The name of the event.

    • listener: ((...args: any[]) => void)

      The callback function

        • (...args: any[]): void
        • Parameters

          • Rest ...args: any[]

          Returns void

    Returns Client

  • Adds a one-timelistener function for the event named eventName to the_beginning_ of the listeners array. The next time eventName is triggered, this listener is removed, and then invoked.

    server.prependOnceListener('connection', (stream) => {
    console.log('Ah, we have our first user!');
    });

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

    Since

    v6.0.0

    Parameters

    • eventName: string | symbol

      The name of the event.

    • listener: ((...args: any[]) => void)

      The callback function

        • (...args: any[]): void
        • Parameters

          • Rest ...args: any[]

          Returns void

    Returns Client

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

    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');

    Since

    v9.4.0

    Parameters

    • eventName: string | symbol

    Returns Function[]

  • 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.

    Since

    v0.1.26

    Parameters

    • Optional event: string | symbol

    Returns Client

  • Removes the specified listener from the listener array for the event namedeventName.

    const callback = (stream) => {
    console.log('someone connected!');
    };
    server.on('connection', callback);
    // ...
    server.removeListener('connection', callback);

    removeListener() will remove, at most, one instance of a listener from the listener array. If any single listener has been added multiple times to the listener array for the specified eventName, then removeListener() must be called multiple times to remove each instance.

    Once an event is emitted, all listeners attached to it at the time of emitting are called in order. This implies that anyremoveListener() or removeAllListeners() calls after emitting and_before_ the last listener finishes execution will not remove them fromemit() in progress. Subsequent events behave as expected.

    const myEmitter = new MyEmitter();

    const callbackA = () => {
    console.log('A');
    myEmitter.removeListener('event', callbackB);
    };

    const callbackB = () => {
    console.log('B');
    };

    myEmitter.on('event', callbackA);

    myEmitter.on('event', callbackB);

    // callbackA removes listener callbackB but it will still be called.
    // Internal listener array at time of emit [callbackA, callbackB]
    myEmitter.emit('event');
    // Prints:
    // A
    // B

    // callbackB is now removed.
    // Internal listener array [callbackA]
    myEmitter.emit('event');
    // Prints:
    // A

    Because listeners are managed using an internal array, calling this will change the position indices of any listener registered after the listener being removed. This will not impact the order in which listeners are called, but it means that any copies of the listener array as returned by the emitter.listeners() method will need to be recreated.

    When a single function has been added as a handler multiple times for a single event (as in the example below), removeListener() will remove the most recently added instance. In the example the once('ping')listener is removed:

    const ee = new EventEmitter();

    function pong() {
    console.log('pong');
    }

    ee.on('ping', pong);
    ee.once('ping', pong);
    ee.removeListener('ping', pong);

    ee.emit('ping');
    ee.emit('ping');

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

    Since

    v0.1.26

    Parameters

    • eventName: string | symbol
    • listener: ((...args: any[]) => void)
        • (...args: any[]): void
        • Parameters

          • Rest ...args: any[]

          Returns void

    Returns Client

  • 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 toInfinity (or 0) to indicate an unlimited number of listeners.

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

    Since

    v0.3.5

    Parameters

    • n: number

    Returns Client

  • 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, v14.17.0

    Parameters

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

    Returns Function[]

  • 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

  • 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:

    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

    Returns

    that iterates eventName events emitted by the emitter

    Parameters

    • emitter: EventEmitter
    • eventName: string

      The name of the event being listened for

    • Optional options: StaticEventEmitterOptions

    Returns AsyncIterableIterator<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[]>

  • 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 EventEmitter.setMaxListeners() method allows the default limit to be modified (if eventTargets is empty) or modify the limit specified in every EventTarget | EventEmitter passed as arguments. The value can be set toInfinity (or 0) to indicate an unlimited number of listeners.

    EventEmitter.setMaxListeners(20);
    // Equivalent to
    EventEmitter.defaultMaxListeners = 20;

    const eventTarget = new EventTarget();
    // Only way to increase limit for `EventTarget` instances
    // as these doesn't expose its own `setMaxListeners` method
    EventEmitter.setMaxListeners(20, eventTarget);

    Since

    v15.3.0, v14.17.0

    Parameters

    • Optional n: number
    • Rest ...eventTargets: (DOMEventTarget | EventEmitter)[]

    Returns void

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