node/test/parallel/test-event-emitter-once.js

'use strict';
require('../common');
var assert = require('assert');
var events = require('events');

var e = new events.EventEmitter();
var times_hello_emited = 0;

e.once('hello', function(a, b) {
  times_hello_emited++;
});

e.emit('hello', 'a', 'b');
e.emit('hello', 'a', 'b');
e.emit('hello', 'a', 'b');
e.emit('hello', 'a', 'b');

var remove = function() {
  assert.fail(1, 0, 'once->foo should not be emitted', '!');
};

e.once('foo', remove);
e.removeListener('foo', remove);
e.emit('foo');

process.on('exit', function() {
  assert.equal(1, times_hello_emited);
});

var times_recurse_emitted = 0;

e.once('e', function() {
  e.emit('e');
  times_recurse_emitted++;
});

e.once('e', function() {
  times_recurse_emitted++;
});

e.emit('e');

process.on('exit', function() {
  assert.equal(2, times_recurse_emitted);
});