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Class Reduce<T, A>

A transform stream that reduces items using the provided function

Readable
 .from([1, 2, 3, 4])
 .pipe(new Reduce((item: number, accumulator: number) => accumulator + item, 0))
 .on("close", (chunks: number[]) => {
     console.log(chunks); // [10]
 });

Type parameters

  • T

    the type of record passed down by previous streams

  • A

    the type of aggregation result

Hierarchy

Implements

  • ReadableStream
  • Writable

Index

Constructors

Properties

Methods

Constructors

constructor

  • new Reduce(reducer: Reducer<T, A>, accumulator: A, opts?: TransformOptions): Reduce

  • Parameters

    • reducer: Reducer<T, A>

      The reducer function used to aggregate items

    • accumulator: A
    • Default value opts: TransformOptions = {}

      The stream's options

    Returns Reduce

Properties

Private accumulator

accumulator: A

destroyed

destroyed: boolean

readable

readable: boolean

readableHighWaterMark

readableHighWaterMark: number

readableLength

readableLength: number

readableObjectMode

readableObjectMode: boolean

Private reducer

reducer: Reducer<T, A>

The reducer function used to aggregate items

writable

writable: boolean

writableCorked

writableCorked: number

writableEnded

writableEnded: boolean

writableFinished

writableFinished: boolean

writableHighWaterMark

writableHighWaterMark: number

writableLength

writableLength: number

writableObjectMode

writableObjectMode: boolean

Methods

[Symbol.asyncIterator]

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

_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

          • 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

_flush

  • _flush(callback: TransformCallback): void

_read

  • _read(size: number): void

  • Parameters

    • size: number

    Returns void

_transform

  • _transform(object: T, _: string, callback: TransformCallback): void

  • Parameters

    • object: T
    • _: string
    • callback: TransformCallback

    Returns void

_write

  • _write(chunk: any, encoding: string, callback: (error?: Error | null) => void): void

  • Parameters

    • chunk: any
    • encoding: string
    • callback: (error?: Error | null) => void
        • (error?: Error | null): void

        • Parameters

          • Optional error: Error | null

          Returns void

    Returns void

Optional _writev

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

  • Parameters

    • chunks: Array<{ chunk: any; encoding: string }>
    • 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: "end", listener: () => void): this
  • addListener(event: "readable", listener: () => void): this
  • addListener(event: "error", listener: (err: Error) => void): this
  • addListener(event: string | symbol, listener: (...args: any[]) => void): this

  • Event emitter The defined events on documents including:

    1. close
    2. data
    3. end
    4. readable
    5. error

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

        • Returns void

    Returns this

  • Parameters

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

        • Returns void

    Returns this

  • Parameters

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

        • Parameters

          • err: Error

          Returns void

    Returns this

  • Parameters

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

        • Parameters

          • Rest ...args: any[]

          Returns void

    Returns this

cork

  • cork(): void

  • Returns void

destroy

  • destroy(error?: Error): void

  • Parameters

    • Optional error: Error

    Returns void

emit

  • emit(event: "close"): boolean
  • emit(event: "data", chunk: any): boolean
  • emit(event: "end"): boolean
  • emit(event: "readable"): boolean
  • emit(event: "error", err: Error): boolean
  • emit(event: string | symbol, ...args: any[]): boolean

  • Parameters

    • event: "close"

    Returns boolean

  • Parameters

    • event: "data"
    • chunk: any

    Returns boolean

  • Parameters

    • event: "end"

    Returns boolean

  • Parameters

    • event: "readable"

    Returns boolean

  • Parameters

    • event: "error"
    • err: Error

    Returns boolean

  • Parameters

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

    Returns boolean

end

  • end(cb?: undefined | (() => void)): void
  • end(chunk: any, cb?: undefined | (() => void)): void
  • end(chunk: any, encoding?: undefined | string, cb?: undefined | (() => void)): void

  • Parameters

    • Optional cb: undefined | (() => void)

    Returns void

  • Parameters

    • chunk: any
    • Optional cb: undefined | (() => void)

    Returns void

  • Parameters

    • chunk: any
    • Optional encoding: undefined | string
    • Optional cb: undefined | (() => void)

    Returns void

eventNames

  • eventNames(): Array<string | symbol>

  • Returns Array<string | symbol>

getMaxListeners

  • getMaxListeners(): number

isPaused

  • isPaused(): boolean

  • Returns boolean

listenerCount

  • listenerCount(type: string | symbol): number

  • Parameters

    • type: string | symbol

    Returns number

listeners

  • listeners(event: string | symbol): Function[]

  • Parameters

    • event: string | symbol

    Returns Function[]

off

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

  • Parameters

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

        • Parameters

          • Rest ...args: any[]

          Returns void

    Returns this

on

  • on(event: "close", listener: () => void): this
  • on(event: "data", listener: (chunk: any) => void): this
  • on(event: "end", listener: () => void): this
  • on(event: "readable", listener: () => void): this
  • on(event: "error", listener: (err: Error) => 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: "end"
    • listener: () => void
        • (): void

        • Returns void

    Returns this

  • Parameters

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

        • Returns void

    Returns this

  • Parameters

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

        • Parameters

          • err: Error

          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: "end", listener: () => void): this
  • once(event: "readable", listener: () => void): this
  • once(event: "error", listener: (err: Error) => 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: "end"
    • listener: () => void
        • (): void

        • Returns void

    Returns this

  • Parameters

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

        • Returns void

    Returns this

  • Parameters

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

        • Parameters

          • err: Error

          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

  • Returns this

pipe

  • pipe<T>(destination: T, options?: undefined | { end?: undefined | false | true }): T

  • Type parameters

    • T: WritableStream

    Parameters

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

    Returns T

prependListener

  • prependListener(event: "close", listener: () => void): this
  • prependListener(event: "data", listener: (chunk: any) => void): this
  • prependListener(event: "end", listener: () => void): this
  • prependListener(event: "readable", listener: () => void): this
  • prependListener(event: "error", listener: (err: Error) => 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: "end"
    • listener: () => void
        • (): void

        • Returns void

    Returns this

  • Parameters

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

        • Returns void

    Returns this

  • Parameters

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

        • Parameters

          • err: Error

          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: "end", listener: () => void): this
  • prependOnceListener(event: "readable", listener: () => void): this
  • prependOnceListener(event: "error", listener: (err: Error) => 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: "end"
    • listener: () => void
        • (): void

        • Returns void

    Returns this

  • Parameters

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

        • Returns void

    Returns this

  • Parameters

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

        • Parameters

          • err: Error

          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?: undefined | string): boolean

  • Parameters

    • chunk: any
    • Optional encoding: undefined | string

    Returns boolean

rawListeners

  • rawListeners(event: string | symbol): Function[]

  • Parameters

    • event: string | symbol

    Returns Function[]

read

  • read(size?: undefined | number): any

  • Parameters

    • Optional size: undefined | number

    Returns any

removeAllListeners

  • removeAllListeners(event?: string | symbol): this

  • Parameters

    • Optional event: string | symbol

    Returns this

removeListener

  • removeListener(event: "close", listener: () => void): this
  • removeListener(event: "data", listener: (chunk: any) => void): this
  • removeListener(event: "end", listener: () => void): this
  • removeListener(event: "readable", listener: () => void): this
  • removeListener(event: "error", listener: (err: Error) => 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: "end"
    • listener: () => void
        • (): void

        • Returns void

    Returns this

  • Parameters

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

        • Returns void

    Returns this

  • Parameters

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

        • Parameters

          • err: Error

          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

  • Returns this

setDefaultEncoding

  • setDefaultEncoding(encoding: string): this

  • Parameters

    • encoding: string

    Returns this

setEncoding

  • setEncoding(encoding: string): this

  • Parameters

    • encoding: string

    Returns this

setMaxListeners

  • setMaxListeners(n: number): this

  • Parameters

    • n: number

    Returns this

uncork

  • uncork(): void

  • Returns void

unpipe

  • unpipe(destination?: NodeJS.WritableStream): this

  • Parameters

    • Optional destination: NodeJS.WritableStream

    Returns this

unshift

  • unshift(chunk: any, encoding?: BufferEncoding): void

  • Parameters

    • chunk: any
    • Optional encoding: BufferEncoding

    Returns void

wrap

  • wrap(oldStream: ReadableStream): this

  • Parameters

    • oldStream: ReadableStream

    Returns this

write

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

  • Parameters

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

    Returns boolean

  • Parameters

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

    Returns boolean

Static from

  • from(iterable: Iterable<any> | AsyncIterable<any>, options?: ReadableOptions): Readable

  • A utility method for creating Readable Streams out of iterators.

    Parameters

    • iterable: Iterable<any> | AsyncIterable<any>
    • Optional options: ReadableOptions

    Returns Readable

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