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Making an object in Javascript?

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Started by Alpha_ProgDes April 03, 2014 05:42 PM

5 comments, last by smr 10 years ago

Alpha_ProgDes

6,963

Author

April 03, 2014 05:42 PM

I know you can do something like this:


var obj = {stuff: 'blah', work: function foo () {return 1}; place: 'bar'};

But you can also do this, I believe:


var obj = function () 
          { 
             this.stuff = 'blah', 
             this.work = function foo () {return 1}, 
             this.place = 'bar'
          };

So is there a difference between creating an object with a function as opposed to object notation? When would I use one over the other?

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fastcall22

10,918

April 03, 2014 06:08 PM

Depends on the paradigm you wish to use, OOP or data-driven. Mozilla has a detailed article on OOP programming in javascript which may answer some of your questions.

rpiller

838

April 03, 2014 10:18 PM

I'm not a big javascript guy, but I don't think it really matters in your specific example. I mean you are creating objects not classes. So I would think you could do it however you want. When it comes to creating "classes" then you have a couple choices.

dmatter

4,872

April 03, 2014 10:39 PM

The main consideration would be that the literal object notation just creates a single object, whereas the function is a constructor from which you can instantiate many new independent objects, rather like a class in some other mainstream OO language.

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Krohm

5,051

April 07, 2014 07:02 AM

But you can also do this, I believe:
<snippet removed>

While this is valid, I'm not sure it is going to work as you expect as you need to provide the function an object to use as this. This task is normally carried out by new, but last time I tried (about two months ago) new would only allow ctors to be real first-level functions, not lambdas.

That is, calling new(obj) didn't work and thrown an exception.

Previously "Krohm"

Alpha_ProgDes

6,963

Author

April 07, 2014 12:55 PM

But you can also do this, I believe:
<snippet removed>

While this is valid, I'm not sure it is going to work as you expect as you need to provide the function an object to use as this. This task is normally carried out by new, but last time I tried (about two months ago) new would only allow ctors to be real first-level functions, not lambdas.

That is, calling new(obj) didn't work and thrown an exception.

Assume that I expect nothing and am wanting to learn the difference between the two :)

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smr

2,468

April 07, 2014 01:36 PM

There are constructors in JavaScript, which is what your example demonstrates. Also using a function to define your object with a constructor will enable typeof and instanceof to return more specific result than just "object". You can reference the constructor with .prototype.constructor. Leveraging that property enables a sort of classical oop style inheritance to be implemented.

function Base(a, b) {}

function Derived (a, b) {
Base.prototype.constructor.call(this, a, b);
}
Derived.prototype = Object.create(Base.prototype);
Derived.prototype.constructor = Derived;

Making an object in Javascript?

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