Function onceError

test/parallel/test-events-once.js:107–121

()

}

async function onceError() {
  const ee = new EventEmitter();

  const expected = new Error('kaboom');
  process.nextTick(() => {
    ee.emit('error', expected);
  });

  const promise = once(ee, 'error');
  assert.strictEqual(ee.listenerCount('error'), 1);
  const [ err ] = await promise;
  assert.strictEqual(err, expected);
  assert.strictEqual(ee.listenerCount('error'), 0);
  assert.strictEqual(ee.listenerCount('myevent'), 0);
}

async function onceWithEventTarget() {
  const et = new EventTarget();