phase 5 part 3: mongodb, elasticsearch hybrid search, data-pipeline, nodejs BFF topics with verified examples

topics/backend/nodejs/examples/express-bff/server.ts

@@ -0,0 +1,17 @@
+// 不自动运行：启动服务 node server.ts，然后 curl -N -X POST localhost:3000/chat -H 'content-type: application/json' -d '{"question":"退货"}'
+import { createApp } from "./app.ts";
+
+async function* fakeLLM(q: string, signal: AbortSignal) {
+  for (const t of ["关于", `“${q}”`, "：", "签收 7 天内", "可以申请退货。"]) {
+    if (signal.aborted) return;
+    await new Promise((r) => setTimeout(r, 200));
+    yield t;
+  }
+}
+
+const app = createApp({
+  askLLM: fakeLLM,
+  findOrder: async (id) => (id === "A001" ? { id, status: "paid" } : null),
+});
+const port = Number(process.env.PORT ?? 3000);
+app.listen(port, () => console.log(`listening on http://127.0.0.1:${port}`));