events.js

/**
 * Module exports.
 */

/**
 * Check if `obj` is an array.
 */

function isArray(obj) {
  return '[object Array]' == {}.toString.call(obj);
}

/**
 * Event emitter constructor.
 *
 * @api public.
 */

function EventEmitter(){};

/**
 * Adds a listener.
 *
 * @api public
 */

EventEmitter.prototype.on = function (name, fn) {
  if (!this.$events) {
    this.$events = {};
  }

  if (!this.$events[name]) {
    this.$events[name] = fn;
  } else if (isArray(this.$events[name])) {
    this.$events[name].push(fn);
  } else {
    this.$events[name] = [this.$events[name], fn];
  }

  return this;
};

EventEmitter.prototype.addListener = EventEmitter.prototype.on;

/**
 * Adds a volatile listener.
 *
 * @api public
 */

EventEmitter.prototype.once = function (name, fn) {
  var self = this;

  function on () {
    self.removeListener(name, on);
    fn.apply(this, arguments);
  };

  on.listener = fn;
  this.on(name, on);

  return this;
};

/**
 * Removes a listener.
 *
 * @api public
 */

EventEmitter.prototype.removeListener = function (name, fn) {
  if (this.$events && this.$events[name]) {
    var list = this.$events[name];

    if (isArray(list)) {
      var pos = -1;

      for (var i = 0, l = list.length; i < l; i++) {
        if (list[i] === fn || (list[i].listener && list[i].listener === fn)) {
          pos = i;
          break;
        }
      }

      if (pos < 0) {
        return this;
      }

      list.splice(pos, 1);

      if (!list.length) {
        delete this.$events[name];
      }
    } else if (list === fn || (list.listener && list.listener === fn)) {
      delete this.$events[name];
    }
  }

  return this;
};

/**
 * Removes all listeners for an event.
 *
 * @api public
 */

EventEmitter.prototype.removeAllListeners = function (name) {
  if (name === undefined) {
    this.$events = {};
    return this;
  }

  if (this.$events && this.$events[name]) {
    this.$events[name] = null;
  }

  return this;
};

/**
 * Gets all listeners for a certain event.
 *
 * @api publci
 */

EventEmitter.prototype.listeners = function (name) {
  if (!this.$events) {
    this.$events = {};
  }

  if (!this.$events[name]) {
    this.$events[name] = [];
  }

  if (!isArray(this.$events[name])) {
    this.$events[name] = [this.$events[name]];
  }

  return this.$events[name];
};

/**
 * Emits an event.
 *
 * @api public
 */

EventEmitter.prototype.emit = function (name) {
  if (!this.$events) {
    return false;
  }

  var handler = this.$events[name];

  if (!handler) {
    return false;
  }

  var args = [].slice.call(arguments, 1);

  if ('function' == typeof handler) {
    handler.apply(this, args);
  } else if (isArray(handler)) {
    var listeners = handler.slice();

    for (var i = 0, l = listeners.length; i < l; i++) {
      listeners[i].apply(this, args);
    }
  } else {
    return false;
  }

  return true;
};