class.js

Class MyStream extends stream.Writable {
  constructor() {
    super({objectMode: true})
  }
 _write(chunk, _, next) {
   next();
  }
  _final(done) {
    done();
  }
}
const mystream = new MyStream();

function.js

const mystream = new stream.Writable({
  objectMode: true,
  write(chunk, _, next) {
    next();
  },
  final(done) {
    done();
  }
});