Simplified EventEmitter like objects

createEmitter.js

function createEmitter() {
  // not ideal when many simple emitters are needed
  // returns object similar to node.js EventEmitter API
  // not compatible with DOM nodes, only JS controllers
  var
    // on, off, emit as immutable and non enumerable
    // all methods returns the implicitly bound emitter
    emitter = Object.create(null, {
      on: {value: function (type, handler) {
        var tmp = get(type);
        if (tmp.indexOf(handler) < 0) {
          tmp.push(handler);
        }
        return emitter;
      }},
      off: {value: function (type, handler) {
        var tmp = get(type), i = tmp.indexOf(handler);
        if (-1 < i) {
          tmp.splice(i, 1);
        }
        return emitter;
      }},
      emit: {value: function (type, handler) {
        var tmp = get(type);
        tmp.forEach(
          emit,
          tmp.slice.call(arguments, 1)
        );
        return emitter;
      }}
    }),
    // private Dictionary for listeners
    listeners = Object.create(null)
  ;
  // private methods
  function emit(handler) {
    handler.apply(emitter, this);
  }
  function get(type) {
    return listeners[type] || (listeners[type] = []);
  }
  return emitter;
}