Instantiate ES6 class from variable

Question

Is there a way to instantiate a new object from a class based on a variable in ES6?

This is my scenario:

class SomeClass {
    hasMany(what){

        var instance = new window[what]();

        var owned_objects = instance.allOwnedBy(this.constructor.name, self.id);

        return instance;
    }
}

However, this returns Uncaught TypeError: window.Group is not a constructor(…)

the hasMany is located within a Class. So what I want to achieve is that the function within this class, should instantiate another class based on the name of that class passed as a variable, and then return the instance.

I assume the `Group` class is not defined in the global scope? — GOTO 0, Sep 29 '16 at 21:39
Correct @GOTO. the window[what] was a far fetch. I tried with just new what(). I tried: this[what] = what, and new what() etc. the Group class is just defined with: class Group { ... — Ole Haugset, Sep 29 '16 at 21:40
@OleHaugset If you don't have any moral concerns using `eval`, you could try `var instance = new (eval(what))();` — GOTO 0, Sep 29 '16 at 21:44
That works @GOTO, but the gut feeling is just that its terribly wrong :P — Ole Haugset, Sep 29 '16 at 22:17

ezakto · Answer 1 · 2016-09-29T21:38:39.213

0

How are you defining class Group?

In my tests, it'd work if you specifically set the class as a property of window. So:

window.Group = class {...}

Then you can do:

var instance = new window['Group']();

edited Sep 29 '16 at 21:38

answered Sep 29 '16 at 21:36

ezakto

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It would work, yes, but you still shouldn't do that. – Bergi Sep 29 '16 at 21:36
1

I'm not really a "don't pollute the window object" activist, but yeah. He could also make a dict with all the references and access that. – ezakto Sep 29 '16 at 21:40

Instantiate ES6 class from variable

1 Answers1