Make an eventing system mix-in that adds .trigger() and .on() to any input object.

eventingLibrary.js

/*
Example usage:
var obj = mixEvents({ name: 'Alice', age: 30 });
obj.on('ageChange', function(){ // On takes an event name and a callback function
  console.log('Age changed');
});
obj.age++;
obj.trigger('ageChange'); // This should call our callback! Should log 'age changed'.
*/

var mixEvents = function(obj) {
  var events = {};

  obj.trigger = function (event) {
    if(!events[event]) {
      return;
    }
    else {
      var args = Array.prototype.slice.call(arguments).slice(1);
      events[event].forEach(function(callback){
        !args.length ? callback() : callback.apply(null, args)
      })
    }
  };

  // Register a callback to be fired on this event.
  obj.on = function (event, callback) {
    !events[event] ? events[event] = [callback] : events[event].push(callback)
  };
  return obj;
};