file

File read and write streams for Node.js and the browser.

Install

npm install @datastream/file

fileReadStream Readable

Reads a file as a stream.

• Node.js: Uses fs.createReadStream
• Browser: Uses window.showOpenFilePicker (File System Access API)

Options

Option	Type	Description
path	string	File path (Node.js)
types	object[]	File type filter for the file picker (see below)

Example — Node.js

import { pipeline } from '@datastream/core'
import { fileReadStream } from '@datastream/file'

await pipeline([
  fileReadStream({ path: './data.csv' }),
])

Example — Browser

import { fileReadStream } from '@datastream/file'

const stream = await fileReadStream({
  types: [{ accept: { 'text/csv': ['.csv'] } }],
})

fileWriteStream Writable

Writes a stream to a file.

• Node.js: Uses fs.createWriteStream
• Browser: Uses window.showSaveFilePicker (File System Access API)

Options

Option	Type	Description
path	string	File path (Node.js), suggested file name (Browser)
types	object[]	File type filter

Example — Node.js

import { pipeline, createReadableStream } from '@datastream/core'
import { fileWriteStream } from '@datastream/file'

await pipeline([
  createReadableStream('hello world'),
  fileWriteStream({ path: './output.txt' }),
])

Example — Browser

import { fileWriteStream } from '@datastream/file'

const writable = await fileWriteStream({
  path: 'output.csv',
  types: [{ accept: { 'text/csv': ['.csv'] } }],
})

File type filtering

The types option validates file extensions (Node.js) and configures the file picker dialog (Browser):

const types = [
  {
    accept: {
      'text/csv': ['.csv'],
      'application/json': ['.json'],
    },
  },
]

On Node.js, if types is provided and the file extension doesn’t match, an "Invalid extension" error is thrown.