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Class BufferBuilder

Hierarchy

  • Duplex
    • BufferBuilder

Implements

  • ReadableStream
  • WritableBase

Index

Constructors

constructor

Properties

allowHalfOpen

allowHalfOpen: boolean

If false then the stream will automatically end the writable side when the readable side ends. Set initially by the allowHalfOpen constructor option, which defaults to true.

This can be changed manually to change the half-open behavior of an existing Duplex stream instance, but must be changed before the 'end' event is emitted.

since

v0.9.4

Private chunks

chunks: Uint8Array[]

Readonly closed

closed: boolean

destroyed

destroyed: boolean

Is true after readable.destroy() has been called.

since

v8.0.0

Readonly errored

errored: Error | null

readable

readable: boolean

Is true if it is safe to call read, which means the stream has not been destroyed or emitted 'error' or 'end'.

since

v11.4.0

Readonly readableAborted

readableAborted: boolean

Returns whether the stream was destroyed or errored before emitting 'end'.

since

v16.8.0

experimental

Readonly readableDidRead

readableDidRead: boolean

Returns whether 'data' has been emitted.

since

v16.7.0, v14.18.0

experimental

Readonly readableEncoding

readableEncoding: BufferEncoding | null

Getter for the property encoding of a given Readable stream. The encoding property can be set using the setEncoding method.

since

v12.7.0

Readonly readableEnded

readableEnded: boolean

Becomes true when 'end' event is emitted.

since

v12.9.0

Readonly readableFlowing

readableFlowing: boolean | null

This property reflects the current state of a Readable stream as described in the Three states section.

since

v9.4.0

Readonly readableHighWaterMark

readableHighWaterMark: number

Returns the value of highWaterMark passed when creating this Readable.

since

v9.3.0

Readonly readableLength

readableLength: number

This property contains the number of bytes (or objects) in the queue ready to be read. The value provides introspection data regarding the status of the highWaterMark.

since

v9.4.0

Readonly readableObjectMode

readableObjectMode: boolean

Getter for the property objectMode of a given Readable stream.

since

v12.3.0

Readonly writable

writable: boolean

Readonly writableCorked

writableCorked: number

Readonly writableEnded

writableEnded: boolean

Readonly writableFinished

writableFinished: boolean

Readonly writableHighWaterMark

writableHighWaterMark: number

Readonly writableLength

writableLength: number

Readonly writableNeedDrain

writableNeedDrain: boolean

Readonly writableObjectMode

writableObjectMode: boolean

Methods

Optional [EventEmitter.captureRejectionSymbol]

  • [EventEmitter.captureRejectionSymbol]<K>(error: Error, event: Key<K, DefaultEventMap>, ...args: Args<K, DefaultEventMap>): void

[Symbol.asyncDispose]

  • [Symbol.asyncDispose](): Promise<void>
  • Calls readable.destroy() with an AbortError and returns a promise that fulfills when the stream is finished.

    since

    v20.4.0

    Returns Promise<void>

[Symbol.asyncIterator]

  • [Symbol.asyncIterator](): AsyncIterableIterator<any>

Optional _construct

  • _construct(callback: (error?: Error | null) => void): void
  • Parameters

    • callback: (error?: Error | null) => void
        • (error?: Error | null): void
        • Parameters

          • Optional error: Error | null

          Returns void

    Returns void

_destroy

  • _destroy(error: Error | null, callback: (error?: Error | null) => void): void
  • Parameters

    • error: Error | null
    • callback: (error?: Error | null) => void
        • (error?: Error | null): void
        • Parameters

          • Optional error: Error | null

          Returns void

    Returns void

_final

  • _final(callback: (error?: Error | null) => void): void
  • Parameters

    • callback: (error?: Error | null) => void
        • (error?: Error | null): void
        • Parameters

          • Optional error: Error | null

          Returns void

    Returns void

_read

  • _read(_size: number): void

_write

  • _write(chunk: any, _encoding: BufferEncoding, callback: (error?: Error) => void): void

Optional _writev

  • _writev(chunks: Array<{ chunk: any; encoding: BufferEncoding }>, callback: (error?: Error | null) => void): void
  • Parameters

    • chunks: Array<{ chunk: any; encoding: BufferEncoding }>
    • callback: (error?: Error | null) => void
        • (error?: Error | null): void
        • Parameters

          • Optional error: Error | null

          Returns void

    Returns void

addListener

  • addListener(event: "close", listener: () => void): this
  • addListener(event: "data", listener: (chunk: any) => void): this
  • addListener(event: "drain", listener: () => void): this
  • addListener(event: "end", listener: () => void): this
  • addListener(event: "error", listener: (err: Error) => void): this
  • addListener(event: "finish", listener: () => void): this
  • addListener(event: "pause", listener: () => void): this
  • addListener(event: "pipe", listener: (src: Readable) => void): this
  • addListener(event: "readable", listener: () => void): this
  • addListener(event: "resume", listener: () => void): this
  • addListener(event: "unpipe", listener: (src: Readable) => void): this
  • addListener(event: string | symbol, listener: (...args: any[]) => void): this
  • Event emitter The defined events on documents including:

    1. close
    2. data
    3. drain
    4. end
    5. error
    6. finish
    7. pause
    8. pipe
    9. readable
    10. resume
    11. unpipe

    Parameters

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

    Returns this

  • Parameters

    • event: "data"
    • listener: (chunk: any) => void
        • (chunk: any): void
        • Parameters

          • chunk: any

          Returns void

    Returns this

  • Parameters

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

    Returns this

  • Parameters

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

    Returns this

  • Parameters

    • event: "error"
    • listener: (err: Error) => void
        • Parameters

          Returns void

    Returns this

  • Parameters

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

    Returns this

  • Parameters

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

    Returns this

  • Parameters

    • event: "pipe"
    • listener: (src: Readable) => void
        • (src: Readable): void
        • Parameters

          • src: Readable

          Returns void

    Returns this

  • Parameters

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

    Returns this

  • Parameters

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

    Returns this

  • Parameters

    • event: "unpipe"
    • listener: (src: Readable) => void
        • (src: Readable): void
        • Parameters

          • src: Readable

          Returns void

    Returns this

  • Parameters

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

          • Rest ...args: any[]

          Returns void

    Returns this

asIndexedPairs

  • asIndexedPairs(options?: Pick<ArrayOptions, "signal">): Readable
  • This method returns a new stream with chunks of the underlying stream paired with a counter in the form [index, chunk]. The first index value is 0 and it increases by 1 for each chunk produced.

    since

    v17.5.0

    Parameters

    • Optional options: Pick<ArrayOptions, "signal">

    Returns Readable

    a stream of indexed pairs.

compose

  • compose<T>(stream: T | ComposeFnParam | Iterable<T> | AsyncIterable<T>, options?: { signal: AbortSignal }): T
  • Type parameters

    • T: ReadableStream

    Parameters

    • stream: T | ComposeFnParam | Iterable<T> | AsyncIterable<T>
    • Optional options: { signal: AbortSignal }
      • signal: AbortSignal

    Returns T

cork

  • cork(): void
  • Returns void

destroy

  • destroy(error?: Error): this
  • Destroy the stream. Optionally emit an 'error' event, and emit a 'close' event (unless emitClose is set to false). After this call, the readable stream will release any internal resources and subsequent calls to push() will be ignored.

    Once destroy() has been called any further calls will be a no-op and no further errors except from _destroy() may be emitted as 'error'.

    Implementors should not override this method, but instead implement readable._destroy().

    since

    v8.0.0

    Parameters

    • Optional error: Error

      Error which will be passed as payload in 'error' event

    Returns this

drop

  • drop(limit: number, options?: Pick<ArrayOptions, "signal">): Readable
  • This method returns a new stream with the first limit chunks dropped from the start.

    since

    v17.5.0

    Parameters

    • limit: number

      the number of chunks to drop from the readable.

    • Optional options: Pick<ArrayOptions, "signal">

    Returns Readable

    a stream with limit chunks dropped from the start.

emit

  • emit(event: "close"): boolean
  • emit(event: "data", chunk: any): boolean
  • emit(event: "drain"): boolean
  • emit(event: "end"): boolean
  • emit(event: "error", err: Error): boolean
  • emit(event: "finish"): boolean
  • emit(event: "pause"): boolean
  • emit(event: "pipe", src: Readable): boolean
  • emit(event: "readable"): boolean
  • emit(event: "resume"): boolean
  • emit(event: "unpipe", src: Readable): boolean
  • emit(event: string | symbol, ...args: any[]): boolean
  • Parameters

    • event: "close"

    Returns boolean

  • Parameters

    • event: "data"
    • chunk: any

    Returns boolean

  • Parameters

    • event: "drain"

    Returns boolean

  • Parameters

    • event: "end"

    Returns boolean

  • Parameters

    • event: "error"
    • err: Error

    Returns boolean

  • Parameters

    • event: "finish"

    Returns boolean

  • Parameters

    • event: "pause"

    Returns boolean

  • Parameters

    • event: "pipe"
    • src: Readable

    Returns boolean

  • Parameters

    • event: "readable"

    Returns boolean

  • Parameters

    • event: "resume"

    Returns boolean

  • Parameters

    • event: "unpipe"
    • src: Readable

    Returns boolean

  • Parameters

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

    Returns boolean

end

  • end(cb?: () => void): this
  • end(chunk: any, cb?: () => void): this
  • end(chunk: any, encoding?: BufferEncoding, cb?: () => void): this
  • Parameters

    • Optional cb: () => void
        • (): void
        • Returns void

    Returns this

  • Parameters

    • chunk: any
    • Optional cb: () => void
        • (): void
        • Returns void

    Returns this

  • Parameters

    • chunk: any
    • Optional encoding: BufferEncoding
    • Optional cb: () => void
        • (): void
        • Returns void

    Returns this

eventNames

  • eventNames(): Array<string | symbol & Key2<unknown, DefaultEventMap>>
  • 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) ]
    
    since

    v6.0.0

    Returns Array<string | symbol & Key2<unknown, DefaultEventMap>>

every

  • every(fn: (data: any, options?: Pick<ArrayOptions, "signal">) => boolean | Promise<boolean>, options?: ArrayOptions): Promise<boolean>
  • This method is similar to Array.prototype.every and calls fn on each chunk in the stream to check if all awaited return values are truthy value for fn. Once an fn call on a chunk awaited return value is falsy, the stream is destroyed and the promise is fulfilled with false. If all of the fn calls on the chunks return a truthy value, the promise is fulfilled with true.

    since

    v17.5.0

    Parameters

    • fn: (data: any, options?: Pick<ArrayOptions, "signal">) => boolean | Promise<boolean>

      a function to call on each chunk of the stream. Async or not.

        • (data: any, options?: Pick<ArrayOptions, "signal">): boolean | Promise<boolean>
        • Parameters

          • data: any
          • Optional options: Pick<ArrayOptions, "signal">

          Returns boolean | Promise<boolean>

    • Optional options: ArrayOptions

    Returns Promise<boolean>

    a promise evaluating to true if fn returned a truthy value for every one of the chunks.

filter

  • filter(fn: (data: any, options?: Pick<ArrayOptions, "signal">) => boolean | Promise<boolean>, options?: ArrayOptions): Readable
  • This method allows filtering the stream. For each chunk in the stream the fn function will be called and if it returns a truthy value, the chunk will be passed to the result stream. If the fn function returns a promise - that promise will be awaited.

    since

    v17.4.0, v16.14.0

    Parameters

    • fn: (data: any, options?: Pick<ArrayOptions, "signal">) => boolean | Promise<boolean>

      a function to filter chunks from the stream. Async or not.

        • (data: any, options?: Pick<ArrayOptions, "signal">): boolean | Promise<boolean>
        • Parameters

          • data: any
          • Optional options: Pick<ArrayOptions, "signal">

          Returns boolean | Promise<boolean>

    • Optional options: ArrayOptions

    Returns Readable

    a stream filtered with the predicate fn.

find

  • find<T>(fn: (data: any, options?: Pick<ArrayOptions, "signal">) => data is T, options?: ArrayOptions): Promise<T | undefined>
  • find(fn: (data: any, options?: Pick<ArrayOptions, "signal">) => boolean | Promise<boolean>, options?: ArrayOptions): Promise<any>
  • This method is similar to Array.prototype.find and calls fn on each chunk in the stream to find a chunk with a truthy value for fn. Once an fn call's awaited return value is truthy, the stream is destroyed and the promise is fulfilled with value for which fn returned a truthy value. If all of the fn calls on the chunks return a falsy value, the promise is fulfilled with undefined.

    since

    v17.5.0

    Type parameters

    • T

    Parameters

    • fn: (data: any, options?: Pick<ArrayOptions, "signal">) => data is T

      a function to call on each chunk of the stream. Async or not.

        • (data: any, options?: Pick<ArrayOptions, "signal">): data is T
        • Parameters

          • data: any
          • Optional options: Pick<ArrayOptions, "signal">

          Returns data is T

    • Optional options: ArrayOptions

    Returns Promise<T | undefined>

    a promise evaluating to the first chunk for which fn evaluated with a truthy value, or undefined if no element was found.

  • Parameters

    • fn: (data: any, options?: Pick<ArrayOptions, "signal">) => boolean | Promise<boolean>
        • (data: any, options?: Pick<ArrayOptions, "signal">): boolean | Promise<boolean>
        • Parameters

          • data: any
          • Optional options: Pick<ArrayOptions, "signal">

          Returns boolean | Promise<boolean>

    • Optional options: ArrayOptions

    Returns Promise<any>

flatMap

  • flatMap(fn: (data: any, options?: Pick<ArrayOptions, "signal">) => any, options?: ArrayOptions): Readable
  • This method returns a new stream by applying the given callback to each chunk of the stream and then flattening the result.

    It is possible to return a stream or another iterable or async iterable from fn and the result streams will be merged (flattened) into the returned stream.

    since

    v17.5.0

    Parameters

    • fn: (data: any, options?: Pick<ArrayOptions, "signal">) => any

      a function to map over every chunk in the stream. May be async. May be a stream or generator.

        • (data: any, options?: Pick<ArrayOptions, "signal">): any
        • Parameters

          • data: any
          • Optional options: Pick<ArrayOptions, "signal">

          Returns any

    • Optional options: ArrayOptions

    Returns Readable

    a stream flat-mapped with the function fn.

forEach

  • forEach(fn: (data: any, options?: Pick<ArrayOptions, "signal">) => void | Promise<void>, options?: ArrayOptions): Promise<void>
  • This method allows iterating a stream. For each chunk in the stream the fn function will be called. If the fn function returns a promise - that promise will be awaited.

    This method is different from for await...of loops in that it can optionally process chunks concurrently. In addition, a forEach iteration can only be stopped by having passed a signal option and aborting the related AbortController while for await...of can be stopped with break or return. In either case the stream will be destroyed.

    This method is different from listening to the 'data' event in that it uses the readable event in the underlying machinary and can limit the number of concurrent fn calls.

    since

    v17.5.0

    Parameters

    • fn: (data: any, options?: Pick<ArrayOptions, "signal">) => void | Promise<void>

      a function to call on each chunk of the stream. Async or not.

        • (data: any, options?: Pick<ArrayOptions, "signal">): void | Promise<void>
        • Parameters

          • data: any
          • Optional options: Pick<ArrayOptions, "signal">

          Returns void | Promise<void>

    • Optional options: ArrayOptions

    Returns Promise<void>

    a promise for when the stream has finished.

getMaxListeners

  • getMaxListeners(): number
  • Returns the current max listener value for the EventEmitter which is either set by emitter.setMaxListeners(n) or defaults to {@link defaultMaxListeners}.

    since

    v1.0.0

    Returns number

isPaused

  • isPaused(): boolean
  • The readable.isPaused() method returns the current operating state of the Readable. This is used primarily by the mechanism that underlies the readable.pipe() method. In most typical cases, there will be no reason to use this method directly.

    const readable = new stream.Readable();
    
    readable.isPaused(); // === false
    readable.pause();
    readable.isPaused(); // === true
    readable.resume();
    readable.isPaused(); // === false
    
    since

    v0.11.14

    Returns boolean

iterator

  • iterator(options?: { destroyOnReturn?: boolean }): AsyncIterableIterator<any>
  • The iterator created by this method gives users the option to cancel the destruction of the stream if the for await...of loop is exited by return, break, or throw, or if the iterator should destroy the stream if the stream emitted an error during iteration.

    since

    v16.3.0

    Parameters

    • Optional options: { destroyOnReturn?: boolean }
      • Optional destroyOnReturn?: boolean

        When set to false, calling return on the async iterator, or exiting a for await...of iteration using a break, return, or throw will not destroy the stream. Default: true.

    Returns AsyncIterableIterator<any>

listenerCount

  • listenerCount<K>(eventName: Key<K, DefaultEventMap>, listener?: Listener2<K, DefaultEventMap>): number
  • 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.

    since

    v3.2.0

    Type parameters

    • K

    Parameters

    • eventName: Key<K, DefaultEventMap>

      The name of the event being listened for

    • Optional listener: Listener2<K, DefaultEventMap>

      The event handler function

    Returns number

listeners

  • listeners<K>(eventName: Key<K, DefaultEventMap>): Array<Listener2<K, DefaultEventMap>>
  • 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

    Type parameters

    • K

    Parameters

    • eventName: Key<K, DefaultEventMap>

    Returns Array<Listener2<K, DefaultEventMap>>

map

  • map(fn: (data: any, options?: Pick<ArrayOptions, "signal">) => any, options?: ArrayOptions): Readable
  • This method allows mapping over the stream. The fn function will be called for every chunk in the stream. If the fn function returns a promise - that promise will be awaited before being passed to the result stream.

    since

    v17.4.0, v16.14.0

    Parameters

    • fn: (data: any, options?: Pick<ArrayOptions, "signal">) => any

      a function to map over every chunk in the stream. Async or not.

        • (data: any, options?: Pick<ArrayOptions, "signal">): any
        • Parameters

          • data: any
          • Optional options: Pick<ArrayOptions, "signal">

          Returns any

    • Optional options: ArrayOptions

    Returns Readable

    a stream mapped with the function fn.

off

  • off<K>(eventName: Key<K, DefaultEventMap>, listener: Listener1<K, DefaultEventMap>): this
  • Alias for emitter.removeListener().

    since

    v10.0.0

    Type parameters

    • K

    Parameters

    • eventName: Key<K, DefaultEventMap>
    • listener: Listener1<K, DefaultEventMap>

    Returns this

on

  • on(event: "close", listener: () => void): this
  • on(event: "data", listener: (chunk: any) => void): this
  • on(event: "drain", listener: () => void): this
  • on(event: "end", listener: () => void): this
  • on(event: "error", listener: (err: Error) => void): this
  • on(event: "finish", listener: () => void): this
  • on(event: "pause", listener: () => void): this
  • on(event: "pipe", listener: (src: Readable) => void): this
  • on(event: "readable", listener: () => void): this
  • on(event: "resume", listener: () => void): this
  • on(event: "unpipe", listener: (src: Readable) => void): this
  • on(event: string | symbol, listener: (...args: any[]) => void): this
  • Parameters

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

    Returns this

  • Parameters

    • event: "data"
    • listener: (chunk: any) => void
        • (chunk: any): void
        • Parameters

          • chunk: any

          Returns void

    Returns this

  • Parameters

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

    Returns this

  • Parameters

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

    Returns this

  • Parameters

    • event: "error"
    • listener: (err: Error) => void
        • Parameters

          Returns void

    Returns this

  • Parameters

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

    Returns this

  • Parameters

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

    Returns this

  • Parameters

    • event: "pipe"
    • listener: (src: Readable) => void
        • (src: Readable): void
        • Parameters

          • src: Readable

          Returns void

    Returns this

  • Parameters

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

    Returns this

  • Parameters

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

    Returns this

  • Parameters

    • event: "unpipe"
    • listener: (src: Readable) => void
        • (src: Readable): void
        • Parameters

          • src: Readable

          Returns void

    Returns this

  • Parameters

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

          • Rest ...args: any[]

          Returns void

    Returns this

once

  • once(event: "close", listener: () => void): this
  • once(event: "data", listener: (chunk: any) => void): this
  • once(event: "drain", listener: () => void): this
  • once(event: "end", listener: () => void): this
  • once(event: "error", listener: (err: Error) => void): this
  • once(event: "finish", listener: () => void): this
  • once(event: "pause", listener: () => void): this
  • once(event: "pipe", listener: (src: Readable) => void): this
  • once(event: "readable", listener: () => void): this
  • once(event: "resume", listener: () => void): this
  • once(event: "unpipe", listener: (src: Readable) => void): this
  • once(event: string | symbol, listener: (...args: any[]) => void): this
  • Parameters

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

    Returns this

  • Parameters

    • event: "data"
    • listener: (chunk: any) => void
        • (chunk: any): void
        • Parameters

          • chunk: any

          Returns void

    Returns this

  • Parameters

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

    Returns this

  • Parameters

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

    Returns this

  • Parameters

    • event: "error"
    • listener: (err: Error) => void
        • Parameters

          Returns void

    Returns this

  • Parameters

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

    Returns this

  • Parameters

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

    Returns this

  • Parameters

    • event: "pipe"
    • listener: (src: Readable) => void
        • (src: Readable): void
        • Parameters

          • src: Readable

          Returns void

    Returns this

  • Parameters

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

    Returns this

  • Parameters

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

    Returns this

  • Parameters

    • event: "unpipe"
    • listener: (src: Readable) => void
        • (src: Readable): void
        • Parameters

          • src: Readable

          Returns void

    Returns this

  • Parameters

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

          • Rest ...args: any[]

          Returns void

    Returns this

pause

  • pause(): this
  • The readable.pause() method will cause a stream in flowing mode to stop emitting 'data' events, switching out of flowing mode. Any data that becomes available will remain in the internal buffer.

    const readable = getReadableStreamSomehow();
    readable.on('data', (chunk) => {
      console.log(`Received ${chunk.length} bytes of data.`);
      readable.pause();
      console.log('There will be no additional data for 1 second.');
      setTimeout(() => {
        console.log('Now data will start flowing again.');
        readable.resume();
      }, 1000);
    });
    

    The readable.pause() method has no effect if there is a 'readable' event listener.

    since

    v0.9.4

    Returns this

pipe

  • pipe<T>(destination: T, options?: { end?: boolean | undefined }): T
  • Type parameters

    • T: WritableStream

    Parameters

    • destination: T
    • Optional options: { end?: boolean | undefined }
      • Optional end?: boolean | undefined

    Returns T

prependListener

  • prependListener(event: "close", listener: () => void): this
  • prependListener(event: "data", listener: (chunk: any) => void): this
  • prependListener(event: "drain", listener: () => void): this
  • prependListener(event: "end", listener: () => void): this
  • prependListener(event: "error", listener: (err: Error) => void): this
  • prependListener(event: "finish", listener: () => void): this
  • prependListener(event: "pause", listener: () => void): this
  • prependListener(event: "pipe", listener: (src: Readable) => void): this
  • prependListener(event: "readable", listener: () => void): this
  • prependListener(event: "resume", listener: () => void): this
  • prependListener(event: "unpipe", listener: (src: Readable) => void): this
  • prependListener(event: string | symbol, listener: (...args: any[]) => void): this
  • Parameters

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

    Returns this

  • Parameters

    • event: "data"
    • listener: (chunk: any) => void
        • (chunk: any): void
        • Parameters

          • chunk: any

          Returns void

    Returns this

  • Parameters

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

    Returns this

  • Parameters

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

    Returns this

  • Parameters

    • event: "error"
    • listener: (err: Error) => void
        • Parameters

          Returns void

    Returns this

  • Parameters

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

    Returns this

  • Parameters

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

    Returns this

  • Parameters

    • event: "pipe"
    • listener: (src: Readable) => void
        • (src: Readable): void
        • Parameters

          • src: Readable

          Returns void

    Returns this

  • Parameters

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

    Returns this

  • Parameters

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

    Returns this

  • Parameters

    • event: "unpipe"
    • listener: (src: Readable) => void
        • (src: Readable): void
        • Parameters

          • src: Readable

          Returns void

    Returns this

  • Parameters

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

          • Rest ...args: any[]

          Returns void

    Returns this

prependOnceListener

  • prependOnceListener(event: "close", listener: () => void): this
  • prependOnceListener(event: "data", listener: (chunk: any) => void): this
  • prependOnceListener(event: "drain", listener: () => void): this
  • prependOnceListener(event: "end", listener: () => void): this
  • prependOnceListener(event: "error", listener: (err: Error) => void): this
  • prependOnceListener(event: "finish", listener: () => void): this
  • prependOnceListener(event: "pause", listener: () => void): this
  • prependOnceListener(event: "pipe", listener: (src: Readable) => void): this
  • prependOnceListener(event: "readable", listener: () => void): this
  • prependOnceListener(event: "resume", listener: () => void): this
  • prependOnceListener(event: "unpipe", listener: (src: Readable) => void): this
  • prependOnceListener(event: string | symbol, listener: (...args: any[]) => void): this
  • Parameters

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

    Returns this

  • Parameters

    • event: "data"
    • listener: (chunk: any) => void
        • (chunk: any): void
        • Parameters

          • chunk: any

          Returns void

    Returns this

  • Parameters

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

    Returns this

  • Parameters

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

    Returns this

  • Parameters

    • event: "error"
    • listener: (err: Error) => void
        • Parameters

          Returns void

    Returns this

  • Parameters

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

    Returns this

  • Parameters

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

    Returns this

  • Parameters

    • event: "pipe"
    • listener: (src: Readable) => void
        • (src: Readable): void
        • Parameters

          • src: Readable

          Returns void

    Returns this

  • Parameters

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

    Returns this

  • Parameters

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

    Returns this

  • Parameters

    • event: "unpipe"
    • listener: (src: Readable) => void
        • (src: Readable): void
        • Parameters

          • src: Readable

          Returns void

    Returns this

  • Parameters

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

          • Rest ...args: any[]

          Returns void

    Returns this

push

  • push(chunk: any, encoding?: BufferEncoding): boolean
  • Parameters

    • chunk: any
    • Optional encoding: BufferEncoding

    Returns boolean

rawListeners

  • rawListeners<K>(eventName: Key<K, DefaultEventMap>): Array<Listener2<K, DefaultEventMap>>
  • 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');
    
    since

    v9.4.0

    Type parameters

    • K

    Parameters

    • eventName: Key<K, DefaultEventMap>

    Returns Array<Listener2<K, DefaultEventMap>>

read

  • read(size?: number): any
  • The readable.read() method reads data out of the internal buffer and returns it. If no data is available to be read, null is returned. By default, the data is returned as a Buffer object unless an encoding has been specified using the readable.setEncoding() method or the stream is operating in object mode.

    The optional size argument specifies a specific number of bytes to read. If size bytes are not available to be read, null will be returned unless the stream has ended, in which case all of the data remaining in the internal buffer will be returned.

    If the size argument is not specified, all of the data contained in the internal buffer will be returned.

    The size argument must be less than or equal to 1 GiB.

    The readable.read() method should only be called on Readable streams operating in paused mode. In flowing mode, readable.read() is called automatically until the internal buffer is fully drained.

    const readable = getReadableStreamSomehow();
    
    // 'readable' may be triggered multiple times as data is buffered in
    readable.on('readable', () => {
      let chunk;
      console.log('Stream is readable (new data received in buffer)');
      // Use a loop to make sure we read all currently available data
      while (null !== (chunk = readable.read())) {
        console.log(`Read ${chunk.length} bytes of data...`);
      }
    });
    
    // 'end' will be triggered once when there is no more data available
    readable.on('end', () => {
      console.log('Reached end of stream.');
    });
    

    Each call to readable.read() returns a chunk of data, or null. The chunks are not concatenated. A while loop is necessary to consume all data currently in the buffer. When reading a large file .read() may return null, having consumed all buffered content so far, but there is still more data to come not yet buffered. In this case a new 'readable' event will be emitted when there is more data in the buffer. Finally the 'end' event will be emitted when there is no more data to come.

    Therefore to read a file's whole contents from a readable, it is necessary to collect chunks across multiple 'readable' events:

    const chunks = [];
    
    readable.on('readable', () => {
      let chunk;
      while (null !== (chunk = readable.read())) {
        chunks.push(chunk);
      }
    });
    
    readable.on('end', () => {
      const content = chunks.join('');
    });
    

    A Readable stream in object mode will always return a single item from a call to readable.read(size), regardless of the value of the size argument.

    If the readable.read() method returns a chunk of data, a 'data' event will also be emitted.

    Calling read after the 'end' event has been emitted will return null. No runtime error will be raised.

    since

    v0.9.4

    Parameters

    • Optional size: number

      Optional argument to specify how much data to read.

    Returns any

reduce

  • reduce<T>(fn: (previous: any, data: any, options?: Pick<ArrayOptions, "signal">) => T, initial?: undefined, options?: Pick<ArrayOptions, "signal">): Promise<T>
  • reduce<T>(fn: (previous: T, data: any, options?: Pick<ArrayOptions, "signal">) => T, initial: T, options?: Pick<ArrayOptions, "signal">): Promise<T>
  • This method calls fn on each chunk of the stream in order, passing it the result from the calculation on the previous element. It returns a promise for the final value of the reduction.

    If no initial value is supplied the first chunk of the stream is used as the initial value. If the stream is empty, the promise is rejected with a TypeError with the ERR_INVALID_ARGS code property.

    The reducer function iterates the stream element-by-element which means that there is no concurrency parameter or parallelism. To perform a reduce concurrently, you can extract the async function to readable.map method.

    since

    v17.5.0

    Type parameters

    • T = any

    Parameters

    • fn: (previous: any, data: any, options?: Pick<ArrayOptions, "signal">) => T

      a reducer function to call over every chunk in the stream. Async or not.

        • (previous: any, data: any, options?: Pick<ArrayOptions, "signal">): T
        • Parameters

          • previous: any
          • data: any
          • Optional options: Pick<ArrayOptions, "signal">

          Returns T

    • Optional initial: undefined

      the initial value to use in the reduction.

    • Optional options: Pick<ArrayOptions, "signal">

    Returns Promise<T>

    a promise for the final value of the reduction.

  • Type parameters

    • T = any

    Parameters

    • fn: (previous: T, data: any, options?: Pick<ArrayOptions, "signal">) => T
        • (previous: T, data: any, options?: Pick<ArrayOptions, "signal">): T
        • Parameters

          • previous: T
          • data: any
          • Optional options: Pick<ArrayOptions, "signal">

          Returns T

    • initial: T
    • Optional options: Pick<ArrayOptions, "signal">

    Returns Promise<T>

removeAllListeners

  • removeAllListeners(eventName?: Key<unknown, DefaultEventMap>): this
  • 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 eventName: Key<unknown, DefaultEventMap>

    Returns this

removeListener

  • removeListener(event: "close", listener: () => void): this
  • removeListener(event: "data", listener: (chunk: any) => void): this
  • removeListener(event: "drain", listener: () => void): this
  • removeListener(event: "end", listener: () => void): this
  • removeListener(event: "error", listener: (err: Error) => void): this
  • removeListener(event: "finish", listener: () => void): this
  • removeListener(event: "pause", listener: () => void): this
  • removeListener(event: "pipe", listener: (src: Readable) => void): this
  • removeListener(event: "readable", listener: () => void): this
  • removeListener(event: "resume", listener: () => void): this
  • removeListener(event: "unpipe", listener: (src: Readable) => void): this
  • removeListener(event: string | symbol, listener: (...args: any[]) => void): this
  • Parameters

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

    Returns this

  • Parameters

    • event: "data"
    • listener: (chunk: any) => void
        • (chunk: any): void
        • Parameters

          • chunk: any

          Returns void

    Returns this

  • Parameters

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

    Returns this

  • Parameters

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

    Returns this

  • Parameters

    • event: "error"
    • listener: (err: Error) => void
        • Parameters

          Returns void

    Returns this

  • Parameters

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

    Returns this

  • Parameters

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

    Returns this

  • Parameters

    • event: "pipe"
    • listener: (src: Readable) => void
        • (src: Readable): void
        • Parameters

          • src: Readable

          Returns void

    Returns this

  • Parameters

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

    Returns this

  • Parameters

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

    Returns this

  • Parameters

    • event: "unpipe"
    • listener: (src: Readable) => void
        • (src: Readable): void
        • Parameters

          • src: Readable

          Returns void

    Returns this

  • Parameters

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

          • Rest ...args: any[]

          Returns void

    Returns this

resume

  • resume(): this
  • The readable.resume() method causes an explicitly paused Readable stream to resume emitting 'data' events, switching the stream into flowing mode.

    The readable.resume() method can be used to fully consume the data from a stream without actually processing any of that data:

    getReadableStreamSomehow()
      .resume()
      .on('end', () => {
        console.log('Reached the end, but did not read anything.');
      });
    

    The readable.resume() method has no effect if there is a 'readable' event listener.

    since

    v0.9.4

    Returns this

setDefaultEncoding

  • setDefaultEncoding(encoding: BufferEncoding): this

setEncoding

  • setEncoding(encoding: BufferEncoding): this
  • The readable.setEncoding() method sets the character encoding for data read from the Readable stream.

    By default, no encoding is assigned and stream data will be returned as Buffer objects. Setting an encoding causes the stream data to be returned as strings of the specified encoding rather than as Buffer objects. For instance, calling readable.setEncoding('utf8') will cause the output data to be interpreted as UTF-8 data, and passed as strings. Calling readable.setEncoding('hex') will cause the data to be encoded in hexadecimal string format.

    The Readable stream will properly handle multi-byte characters delivered through the stream that would otherwise become improperly decoded if simply pulled from the stream as Buffer objects.

    const readable = getReadableStreamSomehow();
    readable.setEncoding('utf8');
    readable.on('data', (chunk) => {
      assert.equal(typeof chunk, 'string');
      console.log('Got %d characters of string data:', chunk.length);
    });
    
    since

    v0.9.4

    Parameters

    • encoding: BufferEncoding

      The encoding to use.

    Returns this

setMaxListeners

  • setMaxListeners(n: number): this
  • 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.

    since

    v0.3.5

    Parameters

    • n: number

    Returns this

some

  • some(fn: (data: any, options?: Pick<ArrayOptions, "signal">) => boolean | Promise<boolean>, options?: ArrayOptions): Promise<boolean>
  • This method is similar to Array.prototype.some and calls fn on each chunk in the stream until the awaited return value is true (or any truthy value). Once an fn call on a chunk awaited return value is truthy, the stream is destroyed and the promise is fulfilled with true. If none of the fn calls on the chunks return a truthy value, the promise is fulfilled with false.

    since

    v17.5.0

    Parameters

    • fn: (data: any, options?: Pick<ArrayOptions, "signal">) => boolean | Promise<boolean>

      a function to call on each chunk of the stream. Async or not.

        • (data: any, options?: Pick<ArrayOptions, "signal">): boolean | Promise<boolean>
        • Parameters

          • data: any
          • Optional options: Pick<ArrayOptions, "signal">

          Returns boolean | Promise<boolean>

    • Optional options: ArrayOptions

    Returns Promise<boolean>

    a promise evaluating to true if fn returned a truthy value for at least one of the chunks.

take

  • take(limit: number, options?: Pick<ArrayOptions, "signal">): Readable
  • This method returns a new stream with the first limit chunks.

    since

    v17.5.0

    Parameters

    • limit: number

      the number of chunks to take from the readable.

    • Optional options: Pick<ArrayOptions, "signal">

    Returns Readable

    a stream with limit chunks taken.

toArray

  • toArray(options?: Pick<ArrayOptions, "signal">): Promise<any[]>
  • This method allows easily obtaining the contents of a stream.

    As this method reads the entire stream into memory, it negates the benefits of streams. It's intended for interoperability and convenience, not as the primary way to consume streams.

    since

    v17.5.0

    Parameters

    • Optional options: Pick<ArrayOptions, "signal">

    Returns Promise<any[]>

    a promise containing an array with the contents of the stream.

uncork

  • uncork(): void

unpipe

  • unpipe(destination?: WritableStream): this
  • The readable.unpipe() method detaches a Writable stream previously attached using the pipe method.

    If the destination is not specified, then all pipes are detached.

    If the destination is specified, but no pipe is set up for it, then the method does nothing.

    const fs = require('node:fs');
    const readable = getReadableStreamSomehow();
    const writable = fs.createWriteStream('file.txt');
    // All the data from readable goes into 'file.txt',
    // but only for the first second.
    readable.pipe(writable);
    setTimeout(() => {
      console.log('Stop writing to file.txt.');
      readable.unpipe(writable);
      console.log('Manually close the file stream.');
      writable.end();
    }, 1000);
    
    since

    v0.9.4

    Parameters

    • Optional destination: WritableStream

      Optional specific stream to unpipe

    Returns this

unshift

  • unshift(chunk: any, encoding?: BufferEncoding): void
  • Passing chunk as null signals the end of the stream (EOF) and behaves the same as readable.push(null), after which no more data can be written. The EOF signal is put at the end of the buffer and any buffered data will still be flushed.

    The readable.unshift() method pushes a chunk of data back into the internal buffer. This is useful in certain situations where a stream is being consumed by code that needs to "un-consume" some amount of data that it has optimistically pulled out of the source, so that the data can be passed on to some other party.

    The stream.unshift(chunk) method cannot be called after the 'end' event has been emitted or a runtime error will be thrown.

    Developers using stream.unshift() often should consider switching to use of a Transform stream instead. See the API for stream implementers section for more information.

    // Pull off a header delimited by \n\n.
    // Use unshift() if we get too much.
    // Call the callback with (error, header, stream).
    const { StringDecoder } = require('node:string_decoder');
    function parseHeader(stream, callback) {
      stream.on('error', callback);
      stream.on('readable', onReadable);
      const decoder = new StringDecoder('utf8');
      let header = '';
      function onReadable() {
        let chunk;
        while (null !== (chunk = stream.read())) {
          const str = decoder.write(chunk);
          if (str.includes('\n\n')) {
            // Found the header boundary.
            const split = str.split(/\n\n/);
            header += split.shift();
            const remaining = split.join('\n\n');
            const buf = Buffer.from(remaining, 'utf8');
            stream.removeListener('error', callback);
            // Remove the 'readable' listener before unshifting.
            stream.removeListener('readable', onReadable);
            if (buf.length)
              stream.unshift(buf);
            // Now the body of the message can be read from the stream.
            callback(null, header, stream);
            return;
          }
          // Still reading the header.
          header += str;
        }
      }
    }
    

    Unlike push, stream.unshift(chunk) will not end the reading process by resetting the internal reading state of the stream. This can cause unexpected results if readable.unshift() is called during a read (i.e. from within a _read implementation on a custom stream). Following the call to readable.unshift() with an immediate push will reset the reading state appropriately, however it is best to simply avoid calling readable.unshift() while in the process of performing a read.

    since

    v0.9.11

    Parameters

    • chunk: any

      Chunk of data to unshift onto the read queue. For streams not operating in object mode, chunk must be a {string}, {Buffer}, {TypedArray}, {DataView} or null. For object mode streams, chunk may be any JavaScript value.

    • Optional encoding: BufferEncoding

      Encoding of string chunks. Must be a valid Buffer encoding, such as 'utf8' or 'ascii'.

    Returns void

wrap

  • wrap(stream: ReadableStream): this
  • Prior to Node.js 0.10, streams did not implement the entire node:stream module API as it is currently defined. (See Compatibility for more information.)

    When using an older Node.js library that emits 'data' events and has a pause method that is advisory only, the readable.wrap() method can be used to create a Readable stream that uses the old stream as its data source.

    It will rarely be necessary to use readable.wrap() but the method has been provided as a convenience for interacting with older Node.js applications and libraries.

    const { OldReader } = require('./old-api-module.js');
    const { Readable } = require('node:stream');
    const oreader = new OldReader();
    const myReader = new Readable().wrap(oreader);
    
    myReader.on('readable', () => {
      myReader.read(); // etc.
    });
    
    since

    v0.9.4

    Parameters

    • stream: ReadableStream

      An "old style" readable stream

    Returns this

write

  • write(chunk: any, encoding?: BufferEncoding, cb?: (error: Error | null | undefined) => void): boolean
  • write(chunk: any, cb?: (error: Error | null | undefined) => void): boolean
  • Parameters

    • chunk: any
    • Optional encoding: BufferEncoding
    • Optional cb: (error: Error | null | undefined) => void
        • (error: Error | null | undefined): void
        • Parameters

          • error: Error | null | undefined

          Returns void

    Returns boolean

  • Parameters

    • chunk: any
    • Optional cb: (error: Error | null | undefined) => void
        • (error: Error | null | undefined): void
        • Parameters

          • error: Error | null | undefined

          Returns void

    Returns boolean

Static from

  • from(src: Stream | NodeBlob | ArrayBuffer | string | Iterable<any> | AsyncIterable<any> | AsyncGeneratorFunction | Promise<any> | Object): Duplex
  • A utility method for creating duplex streams.

    • Stream converts writable stream into writable Duplex and readable stream to Duplex.
    • Blob converts into readable Duplex.
    • string converts into readable Duplex.
    • ArrayBuffer converts into readable Duplex.
    • AsyncIterable converts into a readable Duplex. Cannot yield null.
    • AsyncGeneratorFunction converts into a readable/writable transform Duplex. Must take a source AsyncIterable as first parameter. Cannot yield null.
    • AsyncFunction converts into a writable Duplex. Must return either null or undefined
    • Object ({ writable, readable }) converts readable and writable into Stream and then combines them into Duplex where the Duplex will write to the writable and read from the readable.
    • Promise converts into readable Duplex. Value null is ignored.
    since

    v16.8.0

    Parameters

    • src: Stream | NodeBlob | ArrayBuffer | string | Iterable<any> | AsyncIterable<any> | AsyncGeneratorFunction | Promise<any> | Object

    Returns Duplex

Static fromWeb

  • fromWeb(duplexStream: { readable: ReadableStream; writable: WritableStream }, options?: Pick<DuplexOptions, "allowHalfOpen" | "decodeStrings" | "encoding" | "highWaterMark" | "objectMode" | "signal">): Duplex
  • A utility method for creating a Duplex from a web ReadableStream and WritableStream.

    since

    v17.0.0

    experimental

    Parameters

    • duplexStream: { readable: ReadableStream; writable: WritableStream }
      • readable: ReadableStream
      • writable: WritableStream
    • Optional options: Pick<DuplexOptions, "allowHalfOpen" | "decodeStrings" | "encoding" | "highWaterMark" | "objectMode" | "signal">

    Returns Duplex

Static isDisturbed

  • isDisturbed(stream: Readable | ReadableStream): boolean
  • Returns whether the stream has been read from or cancelled.

    since

    v16.8.0

    Parameters

    • stream: Readable | ReadableStream

    Returns boolean

Static toWeb

  • toWeb(streamDuplex: Duplex): { readable: ReadableStream; writable: WritableStream }
  • A utility method for creating a web ReadableStream and WritableStream from a Duplex.

    since

    v17.0.0

    experimental

    Parameters

    • streamDuplex: Duplex

    Returns { readable: ReadableStream; writable: WritableStream }

    • readable: ReadableStream
    • writable: WritableStream

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