eventemitter.js

var _ = require("./misc");
var assert = require("./assert");

function EventEmitter() {
  this.__listeners = {};
}

EventEmitter.prototype.addEventListener = function(evt, fn) {
  assert(typeof fn == "function", "eventemitter: second argument should be a function");
  if (!this.__listeners[evt]) this.__listeners[evt] = [];
  this.__listeners[evt].push(fn);
};

EventEmitter.prototype.removeEventListener = function(evt, fn) {
  if (arguments.length === 0) {
    this.__listeners = {};
    return;
  }
  if (!this.__listeners.hasOwnProperty(evt)) return;
  if (arguments.length === 1) {
    delete this.__listeners[evt];
    return;
  }
  var listeners = this.__listeners[evt];
  var index = listeners.indexOf(fn);
  if (~index) listeners.splice(index, 1);
  if (!listeners.length) delete this.__listeners[evt];
};

EventEmitter.prototype.trigger = function(evt, arg) {
  if (!this.__listeners.hasOwnProperty(evt)) return;
  var listeners = this.__listeners[evt].slice();
  _.each(listeners, listener => {
    try {
      listener(arg);
    } catch(e) {
      console.error(e, e.stack);
    }
  });
};

// aliases
EventEmitter.prototype.on = EventEmitter.prototype.addEventListener;
EventEmitter.prototype.off = EventEmitter.prototype.removeEventListener;

module.exports = EventEmitter;