@harikalyan/capture-duck

Capture JavaScript errors in the browser and Node, normalize stack traces, optionally forward to PostHog, and send browser payloads to your own HTTP ingest (you own the URL, API keys, and database).

Install

npm install @harikalyan/capture-duck

Optional (browser only), for PostHog:

npm install posthog-js

Browser

Use fetch (no axios) to POST JSON to ingestUrl. Global window.onerror / onunhandledrejection handlers fire captureDuck without awaiting so the UI is not blocked.

import posthog from "posthog-js";
import {
  buildPosthogInitOptions,
  initErrorTracking,
  captureDuck,
} from "@harikalyan/capture-duck/browser";

posthog.init(MY_KEY, buildPosthogInitOptions({ apiKey: MY_KEY, host: MY_HOST }));

await initErrorTracking({
  ingestUrl: "https://api.example.com/errors",
  getIngestHeaders: () => ({ Authorization: `Bearer ${token}` }),
  posthogClient: posthog,
  timeoutMs: 8000,
  beforeSend: (payload) => payload,
});

const { ingest } = await captureDuck(err, { context: "checkout" });
if (ingest?.ok) {
  console.log(ingest.data);
}

Node / backend

No database is bundled into the package. You pass a report function that persists the payload (Convex, Prisma, HTTP, etc.).

import { createCaptureDuck } from "@harikalyan/capture-duck/node";

const captureDuck = createCaptureDuck({
  report: async (payload) => {
    await db.errors.insert(payload);
  },
  environment: process.env.NODE_ENV,
});

Security notes

• Browser: use only the public PostHog project key (phc_...).
• Put secrets on your server or in getIngestHeaders, not in frontend bundles.

License

MIT