Make any function have "on", "off", and "trigger" functionality

eventable.js

// Put this in a utility file somewhere.  (Requires Underscore.)

var Eventable = {

  on : function(event, callback) {
      this.events[event] = callback;

      return this;
  },

  off : function(event) {
      delete this.events[event];

      return this;
  },

  trigger : function(event, data) {
      if (_.has(this.events, event)) {
          this.events[event].apply(this, [data]);
      }

      return this;
  },

  eventable : function(scope) {
      scope.events = scope.events || {};

      _.bindAll(scope, "on", "off", "trigger");
  }

};

usage.js

function MySomething() {
   this.eventable(this);
}

_.extend(MySomething.prototype, Eventable);

// elsewhere:

var s = new MySomething();

s.on("something", function() {
   console.log("Something called!");
});

s.trigger("something"); // -> "Something called!"