Access enumeration member of an object in JavaScript

Question

I'm trying to pass an "Options"-Object to the constructor of another object. Options have enumerations which I try to read in another file.

js/mainApp.js:

square = new World(20, 20, null, 0);

var opts = new Options(MODE.SINGLE, REGION.MIDDLE_EAST);
world = new World(0, 0, "img/whatever.png", opts);

js/options.js :

var MODE = {
    SINGLE : 1,
    MULTI  : 2
};

var REGION = {
    MIDDLE_EAST : { xTranslate : -2300, yTranslate: -700, scale : 1.2}
};

function Options(MODE, REGION) {
    this.mode = MODE;
    this.region = REGION;
}

Now in the World constructor I'm getting the error "opts.region is undefined" for the second alert. For some reason the first alert shows the expected "{ xTranslate : -2300, yTranslate: -700, scale : 1.2}"

js/options.js:

var World = ExtendingSomething.extend(
{
    initialize: function(x, y, imageURL, opts) {
        alert (JSON.stringify(opts.region));
        alert (JSON.stringify(opts.region.scale));
        ...
    }
}
);

Edit: I added few information

I don't understand why I'm getting this error is undefined while it works in in this jsfiddle (thanks for creating to Thomas C. G. de Vilhena).

Maybe it's a problem that I'm using different files? still: Why is there no problem with the call opts.region, but as soon as I'm calling opts.region.scale the error opts.region is undefined appears(not opts.region.scale!).

<script type="text/javascript" src="js/mainApp.js"></script>
<script type="text/javascript" src="js/options.js"></script>
<script type="text/javascript" src="js/world.js"></script>

Edit: I needed to add another line of code to understand the problem

ExtendSomething.extend seems to be missing a closing bracket, but apart from that, the code you have posted looks okay to me. Why don't you create a JSFiddle snippet? — Amal Antony
– Amal Antony, Commented Dec 26, 2013 at 13:41
This jsfiddle is working fine. It is a bit different from the code you provided though. — Thomas C. G. de Vilhena
– Thomas C. G. de Vilhena, Commented Dec 26, 2013 at 17:41
the only difference I can see is: 1.) I'm using world as a subclass with an initialize function, 2.) The different functions appear in seperate files. I still can't understand why I'm getting an is undefined error. — Sadık
– Sadık, Commented Dec 26, 2013 at 21:41

Sadık · Accepted Answer · 2013-12-26 23:17:37Z

1

The problem is the constructor call with wrong parameters. There should be some kind of type check, otherwise it gives a TypeError.

remove any wrong call to constructor or add a check

square = new World(20, 20, null, 0);

answered Dec 26, 2013 at 23:17

Sadık

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Sajad Deyargaroo · Accepted Answer · 2013-12-26 22:30:54Z

0

Script files should be loaded in below order.

<script type="text/javascript" src="js/options.js"></script>
<script type="text/javascript" src="js/world.js"></script>
<script type="text/javascript" src="js/mainApp.js"></script>

It seems we are using objects even before they are being loaded.

answered Dec 26, 2013 at 22:30

Sajad Deyargaroo

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1 Comment

Sadık Over a year ago

thank you, I didn't know that. But this did not solve my problem.

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