test-event-emitter-max-listeners.js

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'use strict';
const common = require('../common');
const assert = require('assert');
const events = require('events');
const { inspect } = require('util');
const e = new events.EventEmitter();

e.on('maxListeners', common.mustCall());

// Should not corrupt the 'maxListeners' queue.
e.setMaxListeners(42);

const throwsObjs = [NaN, -1, 'and even this'];

for (const obj of throwsObjs) {
  assert.throws(
    () => e.setMaxListeners(obj),
    {
      code: 'ERR_OUT_OF_RANGE',
      name: 'RangeError',
      message: 'The value of "n" is out of range. ' +
               `It must be a non-negative number. Received ${inspect(obj)}`,
    }
  );

  assert.throws(
    () => events.defaultMaxListeners = obj,
    {
      code: 'ERR_OUT_OF_RANGE',
      name: 'RangeError',
      message: 'The value of "defaultMaxListeners" is out of range. ' +
               `It must be a non-negative number. Received ${inspect(obj)}`,
    }
  );
}

e.emit('maxListeners');

{
  const { EventEmitter, defaultMaxListeners } = events;
  for (const obj of throwsObjs) {
    assert.throws(() => EventEmitter.setMaxListeners(obj), {
      code: 'ERR_OUT_OF_RANGE',
    });
  }

  assert.throws(
    () => EventEmitter.setMaxListeners(defaultMaxListeners, 'INVALID_EMITTER'),
    { code: 'ERR_INVALID_ARG_TYPE' }
  );
}