Make Service

make-service

A type-safe fetch wrapper for building HTTP service clients. Zero dependencies, built on the Standard Schema spec for runtime validation with Zod, Arktype, or any compatible library.

Core API

makeService(baseURL, options?)

Creates an object with HTTP methods bound to a base URL.

import { makeService } from 'make-service'

const api = makeService('https://api.example.com/v1', {
  headers: { 'content-type': 'application/json' },
})

const response = await api.get('/users')
const response = await api.post('/users', { body: { name: 'John' } })
const response = await api.put('/users/:id', { params: { id: '1' }, body: { name: 'Jane' } })
const response = await api.delete('/users/:id', { params: { id: '1' } })
const response = await api.patch('/users/:id', { params: { id: '1' }, body: { active: false } })

Available methods: get, post, put, delete, patch, head, options, connect.

makeFetcher(baseURL, options?)

Like makeService but returns a single function that accepts method in requestInit.

const fetcher = makeFetcher('https://api.example.com')
const response = await fetcher('/users', { method: 'POST', body: { name: 'John' } })

enhancedFetch(url, requestInit?)

Enhanced fetch without base URL binding. Same typed response behavior.

const response = await enhancedFetch('https://api.example.com/users')

typedResponse(response)

Wraps a native Response to add typed json() and text() methods.

const typed = typedResponse(nativeResponse)
const data = await typed.json() // unknown (not any!)

BaseOptions

type BaseOptions = {
  headers?: HeadersInit | (() => HeadersInit | Promise<HeadersInit>)
  requestTransformer?: (request: EnhancedRequestInit) => EnhancedRequestInit | Promise<EnhancedRequestInit>
  responseTransformer?: (response: TypedResponse) => TypedResponse | Promise<TypedResponse>
}

Dynamic headers

Pass a function (sync or async) to compute headers per request:

const api = makeService('https://api.example.com', {
  headers: async () => ({
    authorization: `Bearer ${await getToken()}`,
  }),
})

Request transformer

Runs before headers are merged. Transform the body, add signals, etc:

import { deepSnakeKeys } from 'string-ts'

const api = makeService('https://api.example.com', {
  requestTransformer: (request) => ({
    ...request,
    body: deepSnakeKeys(request.body),
  }),
})

Response transformer

Transform responses after fetch completes:

import { camelKeys } from 'string-ts'

const api = makeService('https://api.example.com', {
  responseTransformer: (response) => {
    const headers = camelKeys(Object.fromEntries(response.headers))
    // extract tokens, update sessions, etc.
    return response
  },
})

Request Options (ServiceRequestInit)

Path params

URL segments with :param syntax are type-checked:

await api.get('/users/:id/posts/:postId', {
  params: { id: '1', postId: '42' },
})
// Resolves to: /users/1/posts/42

Query params

await api.get('/users', { query: { page: '2', limit: '10' } })
// Resolves to: /users?page=2&limit=10

Accepts Record<string, string>, URLSearchParams, string, or entries array. Merges with existing query strings in the path.

Body

JSON-like objects are auto-stringified. FormData, Blob, ReadableStream pass through unchanged:

await api.post('/users', { body: { name: 'John', age: 30 } })
await api.post('/upload', { body: formData })

Trace

Debug hook called after fetch completes:

await api.get('/users', {
  trace: (url, init, response) => {
    console.log(`${init.method} ${url} → ${response.status}`)
  },
})

Headers per request

Request-level headers merge with (and override) base headers. Set a value to undefined or 'undefined' to remove a base header:

await api.get('/public', { headers: { authorization: undefined } })

Typed Responses

All methods return TypedResponse — a Response with enhanced json() and text():

Generic type cast (no validation)

const users = await response.json<User[]>()

Schema validation (runtime safe)

Pass any Standard Schema-compatible schema (Zod, Arktype, etc.):

import { z } from 'zod'

const users = await response.json(
  z.array(z.object({ id: z.number(), name: z.string() }))
)

On validation failure, throws ParseResponseError with .issues array.

Schema with transform

import { deepCamelKeys } from 'string-ts'

const data = await response.json(
  z.object({
    first_name: z.string(),
    last_name: z.string(),
  }).transform(deepCamelKeys)
)
// data is { firstName: string, lastName: string }

Text with types

const email = await response.text<`${string}@${string}`>()
const validated = await response.text(z.string().email())

Utility Functions

mergeHeaders(...entries)

Merge multiple HeadersInit into one Headers object:

const headers = mergeHeaders(
  { 'content-type': 'application/json' },
  new Headers({ authorization: 'Bearer token' }),
)

addQueryToURL(url, params)

addQueryToURL('/users', { page: '1' }) // '/users?page=1'
addQueryToURL('/users?admin=true', { page: '1' }) // '/users?admin=true&page=1'

replaceURLParams(url, params)

replaceURLParams('/users/:id', { id: '42' }) // '/users/42'

makeGetApiURL(baseURL)

Factory for building full URLs:

const getApiURL = makeGetApiURL('https://api.example.com')
getApiURL('/users', { page: '1' }) // 'https://api.example.com/users?page=1'

ensureStringBody(body)

Stringifies JSON-like objects, passes through FormData/Blob/etc. unchanged.

ParseResponseError

Thrown on schema validation failure:

import { ParseResponseError } from 'make-service'

try {
  const data = await response.json(schema)
} catch (error) {
  if (error instanceof ParseResponseError) {
    console.log(error.issues) // [{ message: '...', path: [...] }]
  }
}

Patterns and Real-World Usage

For detailed patterns combining make-service with string-ts, composable-functions, and authentication flows, see references/patterns.md.