file-fetch

file-fetch

file-fetch is a nodeify-fetch compatible fetch for read and write access to the local file system using file: URLs and URIs (including implicit ones using relative paths).

Usage

Read

Reading a file from the file system is as easy as fetching it on the Web. Call fetch with the URL, and the content is provided as Readable stream in res.body. The example below uses an absolute URL, but relative paths are also supported. See the Supported URLs and URIs section for more details.

import fetch from 'file-fetch'

const res = await fetch(new URL('example.js', import.meta.url))

res.body.pipe(process.stdout)

It's also possible to handle the content without streams. The async res.text() method returns the whole content as a string.

import fetch from 'file-fetch'

const res = await fetch(new URL('example.js', import.meta.url))

console.log(await res.text())

A similar method res.json() is available to parse JSON content and return the parsed result.

import fetch from 'file-fetch'

const res = await fetch(new URL('example.js', import.meta.url))

console.log(await res.json())

Write

Writing content to a file is done with the same function but with the PUT method. The content must be provided as a string or a Readable stream object.

import fetch from 'file-fetch'

await fetch('file:///tmp/example.log', {
  method: 'PUT',
  body: 'test'
})

import fetch from 'file-fetch'
import { Readable } from 'readable-stream'

await fetch('file:///tmp/example.log', {
  method: 'PUT',
  body: Readable.from(['test'])
})

Options

file-fetch supports the following non-standard options:

• baseURL: A string or URL used to resolve relative paths and URIs.
• contentType: A string or function to determine the media type based on the file extension or a fixed value. It can be useful if file extensions or media types not covered by mime-db are required.

Custom fetch with fixed baseURL or contentType lookup

Custom fetch instances can be useful if requests should be processed with relative paths to a directory that is not the current working directory. The contentType argument can also be predefined for the instance. The example below shows how to set the baseURL to a relative path of the current script and how to use a custom contentType function:

import { factory as fetchFactory } from 'file-fetch'

const baseURL = new URL('examples', import.meta.url)
const contentType = ext => ext === 'json' ? 'application/ld+json' : 'application/octet-stream'

const fetch = fetchFactory({ baseURL, contentType })

const res = await fetch('example.js')
const text = await res.text()

Supported URLs and URIs

Different styles of URLs and URIs are supported.

Absolute URLs

An absolute URL for a file schema must start with file:///. No further resolve logic is used.

Example:

file:///home/user/tmp/content.txt

URIs

URIs are supported for use cases where a file scheme is required to distinguish identifiers by scheme and if relative paths are required. The relative paths logic is used to resolve the full URL.

Example:

file:tmp/content.txt

Relative paths

Relative paths are resolved with the given baseURL or, if not given, with the working directory.

Example:

tmp/content.txt