API reference

createFetcher

The transport, and how to replace it.

const fetcher = createFetcher({ baseUrl?, defaultHeaders?, serializeParams? });

baseUrlstringdefaults to ''

A fallback origin, used only when the call context supplies none.
An endpoint’s own baseUrl always wins, so setting both does not double the origin.

defaultHeadersRecord<string, string>

Merged under the headers the pipeline resolved, so pipeline headers win.

serializeParams(params) => stringdefaults to defaultSerializeParams

Controls query-string encoding. The default encodes arrays as repeated keys and nested objects as JSON.
Replace it if your backend expects bracket or dot notation.

Writing your own

A fetcher is a function. Implement it to route through your own client, to mock in tests, or to add transport-level retries.

const fetcher: EndpointFetcher = async (request, headers, ctx) => {
  const res = await myClient(ctx.method, `${ctx.baseUrl ?? ''}${ctx.path}`, {
    body: request,
    headers,
    signal: ctx.signal,
  });
  return {
    data: res.body,
    status: res.status,
    statusText: res.statusText,
    ok: res.status < 400,
    headers: res.headers,   // optional, lower-cased
  };
};