fetch-mpx

A dependency-injected HTTP client with pluggable platform fetch, content-type detection, and error mapping.

• ESM, "type": "module", Node 22+
• Yarn 4 (Corepack)
• Vitest for testing
• No build step — ships source directly
• Zero runtime dependencies

Design

fetch-mpx is built around two injected dependencies:

• platformFetch(url, options) — the actual fetch implementation (browser fetch, Node built-in, Tauri's HTTP plugin, etc.)
• mapRequestError(error) — converts platform-specific error strings into Error objects with .code properties

The library provides optional convenience platform adapters (platform-browser, platform-node), but the core is completely platform-agnostic.

Install

yarn add fetch-mpx

Usage

import {createHttpClient} from 'fetch-mpx'

// Create a client with your platform fetch
const {get, post, put, patch, del, ping} = createHttpClient({
  platformFetch: fetch,          // browser built-in
  mapRequestError: error => error, // pass-through, or your own mapper
})

// Use it
const {data, status, headers} = await get('https://api.example.com/todos/1')
const created = await post('https://api.example.com/todos', {title: 'New'})

With platform adapters

import {createHttpClient} from 'fetch-mpx'
import {platformFetch} from 'fetch-mpx/platform-node'

const client = createHttpClient({
  platformFetch,
  mapRequestError: error => error,
})

Content-type detection

import {detectResponseType, RESPONSE_TYPES} from 'fetch-mpx'

detectResponseType('application/json')           // 'json'
detectResponseType('text/html; charset=utf-8')   // 'text'
detectResponseType('audio/mpeg')                 // 'blob'

Error mapping

The mapRequestError function is called whenever the platform fetch throws a string error (e.g. Tauri plugin). It should return an Error object.

const myErrorMapper = errorString => {
  const error = new Error(errorString)
  error.code = 'CUSTOM_CODE'
  return error
}

const client = createHttpClient({
  platformFetch,
  mapRequestError: myErrorMapper,
})

Error clarification

Set clarifyTimeoutError: true in request config to standardize timeout/abort errors:

try {
  await get(url, {timeout: 5000, clarifyTimeoutError: true})
} catch (error) {
  error.name   // 'TimeoutError' or 'AbortError'
  error.code   // 'TIMEOUT' or 'ABORTED'
  error.status // 499
}

License

MIT