如何重写javascript方法并从类中调用？

Question

Excuse the title but I'm not really sure what this is called (Maybe events?):

I have created a class that someone will use:

function cls_something()
{
    this.notify('hello');
}

Now the person using my class creates a method called 'notify' (as instructed by me) in order to listen for notifications and then perform their own custom code using the param I pass:

var something = new cls_something();

something.notify = function(message)
{
    console.log('The notification is ' + message);   
}

How do I call this method from within the class to give him the notification message?

Fiddle

I'm trying to achieve something like this...

websocket = new WebSocket("ws://localhost:10000"); 

websocket.onopen = function(e)
{
    console.log('you are connected');
}

websocket.onmessage = function(e)
{
    console.log('omg wtf ffs, there was an error: ' + e.msg);
}

Answer 1

You can just call this.notify("Message"); You'd probably want to check to see if it's defined first, though.

EDIT 1:

Ok, so your problem here is that you're calling a function straight from the constructor, before it's defined. If it needs to be defined in the constructor, then pass the function as a parameter.

function cls_something(notifyFunction)
{
    notifyFunction('hello');
}

EDIT 2:

Just so we're clear, you can have the user of your class define functions later, if you'd like. You just can't run them straight from the constructor, obviously. If you run them from the constructor, they need to be defined before hand.

Say your class was something like

function cls_something()
{
    this.someFunctionThatIsRunLater = function() {
        this.notify('hello');
    }
}

Then your client can write

var something = new cls_something();

something.notify = function(message)
{
    console.log('The notification is ' + message);   
}

Then, when the client calls

something.someFunctionThatIsRunLater();

Notify will be called.