Preface

Prepend data to a stream or file.

API

import { preface, createPrependGenerator, PrependStream } from "preface"

createPrependGenerator(data)

Create an async generator that prepends data to the incoming stream or async iterable.

Example

import { pipeline } from "node:stream/promises"

const r = new PassThrough()
const g = createPrependGenerator("b")
const w = new PassThrough()

const p = pipeline(r, g, w)
r.end("a")
await p

// w should now hold "ab"

class PrependStream extends Transform

Deprecated: use createPrependGenerator instead.

A transform stream that prepends data to the incoming stream.

new PrependStream(data, options)

Creates a new instance of PrependStream.

• data: String|Buffer|null: The data to prepend to the input stream. Can accept any object in object mode.
• options: Object: Options to pass to the Transform constructor.
• options.enc: String: Encoding of the data to push.

preface<T>(inputStream, data)

Returns a new instance of PrependStream constructed with the specified arguments. This is in a way just a function version to set up the PrependStream class.

• inputStream: AsyncIterable | Iterable<T>
• data: T: Data to prepend to the stream. Can accept any object in object mode.

CLI

Install as a global module to do some awesome:

• First unnamed argument: Data to prepend to the stream.
• -i / --in: Path to input file. Uses standard input if not provided.
• -o / --out: Path to output file. Uses standard output if not provided.

Examples:

• echo 1234 | preface abcd (Try this one!)
• preface abcd < in.txt > out.txt
• preface abcd --in in.txt --out out.txt

License

MIT