gistfile1.js

'use strict';

const stream = require('stream');

class A extends stream.Readable {
  _read() {
  }
}

class B extends stream.Writable {
  _write(buf, _ , cb) {
  }
}

const a = new A();
const b = new B();

b.on('unpipe', () => {
  console.log('unpipe');
});

b.on('error', () => {});

a.pipe(b);

b.prependListener('error', () => {
  process.once('uncaughtException', () => {
    console.log('no unpipe');
  });
  throw new Error;
});



b.emit('error', new Error);