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Fetch JSON safely

Use @antithrow/std's fetch and Response.json() so every network and parsing failure is a typed error.

The recipe​

import { Err, Result } from "antithrow";
import { fetch, Response } from "@antithrow/std";

const data = await Result.do(async function* () {
	const res = yield* fetch("https://api.example.com/user");

	if (!res.ok) {
		yield* new Err({ kind: "http", status: res.status } as const);
	}

	const body = yield* Response.json<User>(res);
	return body;
});

if (data.isOk()) {
	use(data.value);
}

Why both fetch and Response.json​

The globals throw in two different places:

  • fetch() rejects on DNS, TLS, CORS, aborts.
  • Response.json() throws SyntaxError on a non-JSON body (e.g. an HTML error page).

@antithrow/std wraps both so neither can blow past your handler.

Skipping Result.do​

If you only need the happy path and a single error, chain instead:

const data = await fetch("/api").andThen((res) => Response.json<User>(res));

The error type becomes the union of fetch's and Response.json's — typically TypeError | SyntaxError.

See also​