Listen to (own) process.stdout (in Node.js)

Probably a basic question for those familiar with the topic. Consider the following toy program:

  const fs = require('fs');
  process.stdout.on('data', (chunk) => {
    fs.writeFileSync('myfile.txt', chunk, 'utf-8'); // just an example
  });
  process.stdout.write('xyz');

If I run this code just as it is, I get the following error:

  errno: -4053,
  code: 'ENOTCONN',
  syscall: 'read'

I already do not understand why that happens. But it gets even stranger:

When I run the code with a console.log() before it, no error is thrown anymore! However, the listener I defined for the data event seems not to be executed in that case, as no text file is created.

Can someone explain to me why this happens and what I can do get the expected result (here write to myfile.txt)?