何となく Node.js 的な EventEmitter を実装してみた。 ES.next とか使いまくりで普通じゃ使えないけど。

README.md

#Example

function Foo () {
  EventEmitter.call(this);
}
Foo.prototype = mixin(Object.create(EventEmitter.prototype), {
  doSomeThing: function () {
    var data = {};
    //....
    this.emit("doneSomeThing", data)
  }
});

var f = new Foo();
f.on("doneSomeThing", function(data){
  alert(data);
});

eventEmitter.js

function mixin (aTarget, aSource) {
  for (var key of Object.getOwnPropertyNames(aSource)) {
    let desc = Object.getOwnPropertyDescriptor(aSource, key);
    desc.enumerable = false;
    Object.defineProperty(aTarget, key, desc);
  }
  return aTarget;
}
/**
 * @class EventEmitter {{{1
 */
function EventEmitter() {
  this.listeners = new Map;
}
mixin(EventEmitter.prototype,
  /** @lends EventEmitter.prototype */
  {
    emit: function EventEmitter_emit (aType, aData= null) {
      if (!this.listeners.has(aType))
        return;

      for (let callback of this.listeners.get(aType)) {
        try {
          if (typeof callback === "function")
            callback.call(this, aType, aData);
          else
            callback.handleEvent(aType, aData);
        } catch(e) {
          console.error(e);
        }
      }
    },
    addListener: function EventEmitter_addListener (aType, aCallback) {
      if (typeof aCallback !== "function" &&
          (typeof aCallback !== "object" || typeof aCallback.handleEvent !== "function"))
        throw TypeError("callback is not callable.");

      if (this.listeners.has(aType))
        this.listeners.get(aType).add(aCallback);
      else
        this.listeners.set(aType, new Set([aCallback]));

      return this;
    },
    on: function EventEmitter_on (aType, aCallback) {
      this.addListener(aType, aCallback);
      return this;
    },
    once: function EventEmitter_once (aType, aCallback) {
      if (typeof aCallback !== "function" &&
          (typeof aCallback !== "object" || typeof aCallback.handleEvent !== "function"))
        throw TypeError("callback is not callable.");

      this.addListener(aType, function once(type, data) {
        this.removeEventListener(type, once);
        if (typeof aCallback === "function")
          aCallback.call(this, type, data);
        else
          aCallback.handleEvent(type, data);
      });
      return this;
    },
    removeListener: function EventEmitter_removeListener (aType, aCallback) {
      var funcs = this.listeners.get(aType);
      if (funcs)
        return funcs.delete(aCallback);

      return false;
    },
    removeAllListeners: function EventEmitter_removeAllListeners (aType) {
      if (aType)
        this.listeners.delete(aType);
      else {
        for (let [type] of this.listeners)
          this.listeners.delete(type);
      }
      return this;
    },
  }
);