Node.js simple HTTP proxy

app.js

const http = require('node:http')
const https = require('node:https')
const events = require('node:events')
const stream = require('node:stream/promises')

const { env } = process

http
  .createServer(async (clientRequest, clientResponse) => {
    try {
      const url = new URL(clientRequest.url, env.BASE_URL)
      const httpModule = url.protocol === 'https:' ? https : http
      const serverRequest = httpModule.request(url, {
        method: http.request.method,
        headers: Object.assign({}, clientRequest.headers, { host: url.host })
      })
      const requestPipeline = stream.pipeline(clientRequest, serverRequest)
      const [serverResponse] = await events.once(serverRequest, 'response')
      clientResponse.writeHead(serverResponse.statusCode, serverResponse.headers)
      const responsePipeline = stream.pipeline(serverResponse, clientResponse)
      await Promise.all([requestPipeline, responsePipeline])
    } catch (error) {
      // handle `premature close` and `aborted` errors
      console.error(clientRequest.url, error.message)
      if (!clientResponse.headersSent) {
        clientResponse
          .writeHead(500, { 'content-type': 'text/plain' })
          .end(error.message)
      } else {
        clientResponse.end()
      }
    }
  })
  .listen(env.PORT)
  .on('listening', function () {
    const address = this.address()
    const bind = typeof address === 'string'
      ? 'pipe ' + address
      : 'port ' + address.port
    console.log('Listening on ' + bind)
  })
  .on('error', function (error) {
    if (error.syscall !== 'listen') {
      throw error
    }

    const bind = typeof env.PORT === 'string'
      ? 'pipe ' + port
      : 'port ' + port

    switch (error.code) {
      case 'EACCES':
        console.error(bind + ' requires elevated privileges')
        process.exit(1)
      case 'EADDRINUSE':
        console.error(bind + ' is already in use')
        process.exit(1)
      default:
        throw error
    }
  })