Simulate C# like events in javascript

Question

I want to simulate C#'s events in JavaScript: what i want to do is something like this:

Let's say i have the following code:

function addToInvocationList(method, listener) {
      *Some code to add listener to the invocation list of method*
}

function MyClass() {
}

MyClass.prototype.Event = function() {}

var my_class_obj = new MyClass();

function subscriberFunction1() {}
function subscriberFunction2() {}
function subscriberFunction3() {}

addToInvocationList(my_class_obj.Event, subscriberFunction1);
addToInvocationList(my_class_obj.Event, subscriberFunction2);
addToInvocationList(my_class_obj.Event, subscriberFunction3);

my_class_obj.Event();

What i want to do is when i call my_class_obj.Event, all the subscribed functions get called.

Could this be achieved purely in JavaScript or i need to find my way around through DOM events?

Khanh TO · Accepted Answer · 2014-02-05 15:03:50Z

9

How about writing a separate event class: Reference link: http://alexatnet.com/articles/model-view-controller-mvc-javascript

function Event(sender) {
    this._sender = sender;
    this._listeners = [];
}

Event.prototype = {
    attach: function (listener) {
        this._listeners.push(listener);
    },
    notify: function (args) {
        for (var i = 0; i < this._listeners.length; i++) {
            this._listeners[i](this._sender, args);
        }
    }
};

And your my class. For example:

function MyClass(name) {
     var self = this;
     self.Name = name;
     self.nameChanged = new Event(this);

     self.setName = function (newName){
         self.Name = newName;
         self.nameChanged.notify(newName);
     }
}

Subscribe to event example code:

var my_class_obj = new MyClass("Test");
my_class_obj.nameChanged.attach(function (sender,args){

});
my_class_obj.setName("newName");

You can attach more event handlers and all these event handlers will get called. And you can also add more events as you'd like: addressChanged event for example. This approach also simulate c# event (sender and args)

edited Feb 5, 2014 at 15:03

answered Apr 12, 2013 at 6:41

Khanh TO

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2 Comments

hiddenUser Over a year ago

Exactly that's what i figured out, thanks man! This works great! However. i'm wondering about Garbage Collection, what if wanted to remove a handler, how can i make sure it's garbage collected, are anonymous methods garbage collected as soon are their reference is removed??

Khanh TO Over a year ago

well, there should be no difference between anonymous methods and declared methods in this case. We also usually use anonymous methods in jQuery: $(document).ready(function(){});

Andries · Accepted Answer · 2013-04-12 06:01:10Z

0

You could write your own Observer (publisher-subscriber) read the GOF. Or, if using jQuery, custom events (http://api.jquery.com/trigger/) can help you out.

answered Apr 12, 2013 at 6:01

Andries

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