emit, on, once in pure javascript

dom-events.js

Object.prototype.emit = function(name, d) {
  this.dispatchEvent(new CustomEvent(name, { detail: d }));
  return this;
};
Object.prototype.on = function(name, cb) {
  this.addEventListener(name, cb, false);
  return cb;
};
Object.prototype.once = function(name, cb) {
  var wrapper = function() {
    this.removeEventListener(name, wrapper, false); cb.apply(this, arguments);
  };
  this.addEventListener(name, wrapper, false);
  return wrapper;
};

events.js

Object.prototype.$emit = function(name) {
  var args = Array.prototype.slice.call(arguments, 1);
  if (this._events && this._events[name])
    this._events[name].forEach(function(cb) { cb.apply(this, args) }.bind(this));
  return this;
};
Object.prototype.$off = function(name, cb) {
  if (!this._events) return this;
  if (!cb) delete this._events[name];
  if (this._events[name]) this._events[name] = this._events[name].filter(function(i) { return i != cb });
  return this;
};
Object.prototype.$on = function(name, cb) {
  if (!this._events) this._events = {};
  if (!this._events[name]) this._events[name] = [];
  this._events[name].push(cb);
  return cb;
};
Object.prototype.$once = function(name, cb) {
  var wrapper, self = this;
  wrapper = function() { self.$off(name, wrapper); cb.apply(this, arguments); };
  this.$on(name, wrapper);
  return wrapper;
};