Serve a NestJS application from a sub-path using ExpressJS sub-app feature

nestjs-expressjs-sub-app-sub-path.ts

import { ValidationPipe } from '@nestjs/common';
import { NestFactory } from '@nestjs/core';
import { ExpressAdapter } from '@nestjs/platform-express';
import { urlencoded, json } from 'express';

import { AppModule } from './app/app.module';

(async () => {
  const nestExpressAppAdapter = new ExpressAdapter();
  const app = await NestFactory.create(AppModule, nestExpressAppAdapter, {});
  
  // Serve the NestJS app as a sub-app at the base href path:
  const expressAppAdapter = new ExpressAdapter();
  const expressApp = expressAppAdapter.getInstance();
  const nestExpressApp = nestExpressAppAdapter.getInstance();
  const baseHref = process.env.BASE_HREF || '/';
  expressApp.use(baseHref, nestExpressApp);
  await app.init();

  expressApp.listen(appPort, () => {
    console.log(`Listening on port ${appPort}`);
  });
})();