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Logs Events

Log events are distributed by Modern.js as events of type log.

Built-in Events

Based on server-side runtime logic, Modern.js provides the following log events:

StageMessageLevel
RENDER_HTMLApp Render To HTMLerror
RENDER_STREAMAn error occurs during streaming SSRerror
RENDER_SHELLAn error occurs during streaming render shellerror

Modern.js also retains SSR logs from legacy versions using useLoader:

StageMessageLevel
PRERENDERApp Prerendererror
USE_LOADERApp run useLoadererror
TIP

The useLoader API is now deprecated. We recommend migrating to convention-based routing and using Data Loaders for data fetching. Applications already using Data Loaders can enable ssr.disablePrerender to disable prerendering and improve SSR performance.

Built-in Monitor

In Modern.js, log events are handled by LoggerMonitor, which outputs logs to the console.

INFO

The built-in LoggerMonitor depends on the rslog library.

For example, intentionally throwing an error in the project:

routes/page.tsx
import './index.css';

const Index = () => <div className="container-box">{a}</div>;

export default Index;

If running normally, you can see the following output in the console:

> Local:    http://localhost:8080/
> press h + enter to show shortcuts

error   SSR Error - App Prerender, error = ReferenceError: a is not defined
    at Index (/somepath/page.tsx:3:1)