property

ImportMeta.hot

hot: { data: any; accept(): void; dispose(cb: (data: any) => void | Promise<void>): void; off(event: HMREvent, callback: () => void): void; on(event: HMREvent, callback: () => void): void }

Hot module replacement (HMR) APIs. In production this value is undefined, so you can guard HMR code with an if statement:

if (import.meta.hot) {
  // HMR APIs are available
}

The check is usually unnecessary: Bun dead-code-eliminates calls to the HMR APIs in production builds.

https://bun.com/docs/bundler/hmr