NodeJS Fetch: Handle Network Error Type on same fetch request

Question

How I check network error type on same request?

My nodejs code:

try {
   const response= await fetch("https://app.local")
   
} catch (err) {
  console.log(err);
}

I get on console:

TypeError: fetch failed
    at node:internal/deps/undici/undici:12502:13
    at processTicksAndRejections (node:internal/process/task_queues:95:5)
    at StatusController.health (/app/src/src/controllers/status.controller.ts:40:19)
    at /app/src/node_modules/@nestjs/core/router/router-execution-context.js:46:28
    at /app/src/node_modules/@nestjs/core/router/router-proxy.js:9:17 {
  [cause]: Error: getaddrinfo ENOTFOUND app.local
      at GetAddrInfoReqWrap.onlookupall [as oncomplete] (node:dns:120:26) {
    errno: -3008,
    code: 'ENOTFOUND',
    syscall: 'getaddrinfo',
    hostname: 'app.local'
  }
}

I want to check code: 'ENOTFOUND';

... catch (err) {
  if(err.code=='ENOTFOUND') bla bla;
}

But err.code always undefined. err.message output: fetch failed

Answer 1

You can get it with: err.cause.code.

The error type should be checked to be TypeError (see more info: https://developer.mozilla.org/en-US/docs/Web/API/fetch).