Identify specific class of array element? [duplicate]

Question

I have an array (Element[]) that contains different implementations.

Now, what's the proper way to identify the "subclass"/type of an array element? i.e. how do I identify Element[1] as an implementation of RedElement?

export interface Element {
   ...
}

export class RedElement implements Element {
    ...specific functionality/values.
}

export class GreenElement implements Element {
    ...specific functionality/values.
}

const myArr: Element[] = [
    new GreenElement(...params),
    new GreenElement(...otherParams),
    new RedElement(...),
...
]

Now when I later want to work with one of those elements I need to know which type/class it is, but all I'm left with is an Object of type Element.

myArr.forEach(e => {
    e <- has type Element
});

I could obviously add a property that identifies each element as its specific class by a string or enum but that seems not too elegant.

Is there a better way?

You could use (GreenElement | RedElement)[] and check then if(el instanceof GreenElement) etc — Ilijanovic
– Ilijanovic, Commented May 31, 2022 at 11:06
instanceof did not work for me due to an incorrect import... now works like a charm — tippexx
– tippexx, Commented May 31, 2022 at 11:18

ancyrweb · Accepted Answer · 2022-05-31 10:44:57Z

1

Since you are creating classes, you can use instanceof operator to discriminate between your different elements.

myArr.forEach(e => {
    if (e instanceof RedElement) {
        ...
    }
});

answered May 31, 2022 at 10:44

ancyrweb

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