Can we get an object of class using a string in javascript?

Question

Here, i am implementing an GeoMap asset which has all the countries. in this, all countries has their own class such as BTNMongolia, BTNHungary etc. i have only countries name to get object and based on countries name, i want to get object of the country's class. i'm doing like this.

function countryObject(country) {
    switch (country) {
        case 'mongolia':
            return new BTNMongolia();
        case 'mongolia':
            return new BTNHungary();
        case 'mongolia':
            return new BTNComoros();
        case 'mongolia':
            return new BTNAntiguaandBarbuda();
        case 'mongolia':
            return new BTNSouthKorea();
        case 'mongolia':
            return new BTNAustralia();
        case 'mongolia':
            return new BTNTajikistan();
        default:
            return null;
    }
}

here, to get object, i want to get object of the country'class from the country'name itself. is there is a short way to do that?.

possible duplicate of [Get object class from string name in javascript](http://stackoverflow.com/questions/5646279/get-object-class-from-string-name-in-javascript) — Banana, Aug 08 '14 at 11:56

score 3 · Accepted Answer · edited May 23 '17 at 12:20

3

The main idea as below, you will need to check whether it exist to return null :

return new window["BTN" + country.capitalize()]();

If your class under a namespace, you may do it this way:

return new myspaces["BTN" + country.capitalize()]();

As for string capitalize you can refer this post.

edited May 23 '17 at 12:20

Community

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answered Aug 08 '14 at 11:50

Wenbing Li

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Be warned, this doesn't work if your constructors are in a namespace other than `window` – Adam Jenkins Aug 08 '14 at 11:57

score 2 · Answer 2 · edited Aug 08 '14 at 11:59

2

This could be a solution. You can use a dictionary like bellow.

function countryObject(country){
    var countryObject = {
        mongolia:  BTNMongolia,
        hungary:   BTNHungary,
        comoros:   BTNComoros,
        australia: BTNAustralia
        // ...
    };
    return new countryObject[country]();
}

I've not specified the full code. So please extend it.

edited Aug 08 '14 at 11:59

Emissary

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answered Aug 08 '14 at 11:49

Mritunjay

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You don't need to instantiate ***every*** one each time the factory function is called - just reference the constructors and `return new countryObject[country];` – Emissary Aug 08 '14 at 11:51
that doesnt really answer his question, its exactly the same as switch-case logic, he still needs to map everything while he asks how to do it blind without mapping... – Banana Aug 08 '14 at 11:51
@Emissary thanx for the catch, updated my answer now it won't create every time. – Mritunjay Aug 08 '14 at 11:55
1

@Emissary ohhh I got it, What I was thinking they both are same, but when you used the terms then I realized, many many thanx. – Mritunjay Aug 08 '14 at 12:02

score 0 · Answer 3 · edited May 23 '17 at 11:49

0

I believe this questions was already answered here Get object class from string name in javascript. Basically don't use eval, store the list of classes in a map and then look them up in the map.

edited May 23 '17 at 11:49

Community

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answered Aug 08 '14 at 11:55

Eric Maibach

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icke · Answer 4 · 2014-08-08T11:56:58.627

-2

You could try something like return eval('new BTN'+country+'()'). That doesn't seem like a good use of eval, but I can't think of another way of doing it without explicitly listing all the possible classes.

edited Aug 08 '14 at 11:56

answered Aug 08 '14 at 11:48

icke

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Can we get an object of class using a string in javascript?

4 Answers4