JavaScript Object and Prototypes

[Frinavale]

Ok, now that I think I understand how Objects work in JavaScript, I'm off to look up how to implement a Singleton pattern using JavaScript.

[gits]

;) nope ... you could even do (for a specific instance):

function MY_OBJ() {}

MY_OBJ.prototype.my_func = function() {};

var o = new MY_OBJ;

o.my_func = function() { // new code here };

kind regards

[gits]

hmmm ... a singleton :) something like this:

function MY_OBJ() {
    if (this.o != null) {
        return MY_OBJ.prototype.o;
    } else {
        MY_OBJ.prototype.o = this;
    }
}

MY_OBJ.prototype.o = null;

MY_OBJ.prototype.my_func = function() {};
 
var o = new MY_OBJ;

o.foo = 'foo';

alert(o.foo);

var a = new MY_OBJ;

a.foo = 'bar';

alert(a.foo);
alert(o.foo);

kind regards

[Frinavale]

:D

You know what's funny?
I decided that I don't actually want to use the Singleton in my solution.

;)

Thanks again Gits!

[gits]

*lol* ... but it's quite cool ;) ... nope ... serious ... when you have a look at it it makes use of the things we talked about before ... when we first create an instance we overwrite the prototype of the class and when the second instance should be created we just return a ref to the first created object ;)

kind regards

[Frinavale]

when you have a look at it it makes use of the things we talked about before ...

I was thinking the same thing.
It is pretty cool, and thanks to you it makes a lot of sense to me now.

I have a long way to go with JavaScript. As my ASP.NET applications become more complicated I'm finding that I have to use JavaScript more and more. It's a really good thing that you've helped me understand these basics now because I have a feeling everything's about to become a lot more complicated in my future.

[gits]

you know where to find help ;) ... JavaScript is quite cool!! :)

kind regards,
gits

[Dormilich]

What is the name of the ":" notation so that I can look this up?

"Object Literal" (just to give that info)

[Frinavale]

ok .... let's have a closer look at it :) ...

var foo = {
    a: 'some_value',
    b: function() { // whatever code }
};

here you create an instance of an object directly and you declare the properties a and b ... where b stores a reference to the function-code that is assigned to it. note: when you have a look at this ... this is where JSON is not far away ;) just have that as a string from a response and eval it and you have a native js-object ready for use.

I started debugging my original Ajax enabled .net server control (again...becaus e it's not working in IE8... in fact it's crashing IE8 RC1). Upon researching a way around my problems I encountered numerous references to JSON with regards to these types of controls. Curious, I finally looked into JSON and now understand what you were referring to in your comment here.

PS: be aware of the use of the this keyword when working with javascript object ... this always relates to the caller of a function ... so that might be tricky when starting to use objects in JavaScript.

I find it ironic that I had to experience this problem first hand myself even though you warned me about ""this"".