node/test/parallel/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 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'];
const maxError = /^TypeError: "n" argument must be a positive number$/;
const defError = /^TypeError: "defaultMaxListeners" must be a positive number$/;

for (const obj of throwsObjs) {
  assert.throws(() => e.setMaxListeners(obj), maxError);
  assert.throws(() => events.defaultMaxListeners = obj, defError);
}

e.emit('maxListeners');