Add fetchWorker for fetching off the main thread

src/workers/fetch.test.ts

@@ -0,0 +1,14 @@
+import { assert } from '@/deps-test.ts';
+
+import { fetchWorker } from './fetch.ts';
+
+Deno.test('fetchWorker', async () => {
+  await sleep(2000);
+  const response = await fetchWorker('https://example.com');
+  const text = await response.text();
+  assert(text.includes('Example Domain'));
+});
+
+function sleep(ms: number) {
+  return new Promise((resolve) => setTimeout(resolve, ms));
+}

src/workers/fetch.ts

@@ -0,0 +1,19 @@
+import { Comlink } from '@/deps.ts';
+
+import type { FetchWorker } from './fetch.worker.ts';
+
+const _worker = Comlink.wrap<typeof FetchWorker>(
+  new Worker(
+    new URL('./fetch.worker.ts', import.meta.url),
+    { type: 'module' },
+  ),
+);
+
+const fetchWorker: typeof fetch = async (input) => {
+  const url = input instanceof Request ? input.url : input.toString();
+
+  const args = await _worker.fetch(url);
+  return new Response(...args);
+};
+
+export { fetchWorker };

src/workers/fetch.worker.ts

@@ -0,0 +1,17 @@
+import { Comlink } from '@/deps.ts';
+
+export const FetchWorker = {
+  async fetch(url: string): Promise<[BodyInit, ResponseInit]> {
+    const response = await fetch(url);
+    return [
+      await response.text(),
+      {
+        status: response.status,
+        statusText: response.statusText,
+        headers: Array.from(response.headers.entries()),
+      },
+    ];
+  },
+};
+
+Comlink.expose(FetchWorker);