node/lib/events.js

exports.EventEmitter = process.EventEmitter;

// process.EventEmitter is defined in src/node_events.cc
// process.EventEmitter.prototype.emit() is also defined there.
process.EventEmitter.prototype.addListener = function (type, listener) {
  if ('function' !== typeof listener) {
    throw new Error('addListener only takes instances of Function');
  }

  if (!this._events) this._events = {};

  // To avoid recursion in the case that type == "newListeners"! Before
  // adding it to the listeners, first emit "newListeners".
  this.emit("newListener", type, listener);

  if (!this._events[type]) {
    // Optimize the case of one listener. Don't need the extra array object.
    this._events[type] = listener;
  } else if (this._events[type] instanceof Array) {
    // If we've already got an array, just append.
    this._events[type].push(listener);
  } else {
    // Adding the second element, need to change to array.
    this._events[type] = [this._events[type], listener];
  }

  return this;
};

process.EventEmitter.prototype.removeListener = function (type, listener) {
  if ('function' !== typeof listener) {
    throw new Error('removeListener only takes instances of Function');
  }

  // does not use listeners(), so no side effect of creating _events[type]
  if (!this._events || !this._events[type]) return this;

  var list = this._events[type];

  if (list instanceof Array) {
    var i = list.indexOf(listener);
    if (i < 0) return this;
    list.splice(i, 1);
  } else {
    this._events[type] = null;
  }

  return this;
};

process.EventEmitter.prototype.removeAllListeners = function (type) {
  // does not use listeners(), so no side effect of creating _events[type]
  if (!type || !this._events || !this._events[type]) return this;
  this._events[type] = null;
};

process.EventEmitter.prototype.listeners = function (type) {
  if (!this._events) this._events = {};
  if (!this._events[type]) this._events[type] = [];
  if (!(this._events[type] instanceof Array)) {
    this._events[type] = [this._events[type]];
  }
  return this._events[type];
};
exports.Promise = function removed () {
  throw new Error(
    'Promise has been removed. See '+
    'http://groups.google.com/group/nodejs/msg/0c483b891c56fea2 for more information.');
}
process.Promise = exports.Promise;