Typescript: initialize empty array when using extends Array<T>

Question

I am trying to add a method which would belong to a class extending Arrays of device with Typescript (3.7.5).

export class devices extends Array<device> {
    constructor(items?:Array<device>) {
        super(...items);
    }

    getDeviceByUid(uid: number): device {
        return this.filter(elmt => elmt.uid == uid)[0];
    }
}

But I also need to be able to declare and define an empty array, like I would do with a normal array:

unfilteredDeviceList: devices = []; //error : Property 'getDeviceByUid' is missing in type 'undefined[]' but required in type 'devices'.

So I tried like so: unfilteredDeviceList: devices = new devices();

I get no compile time errors when doing the latest, but in runtime : Error: Uncaught (in promise): TypeError: super is not iterable (cannot read property Symbol(Symbol.iterator))

What is the way to declare and define an extended empty array, or what should I change in the constructor?

Eugene Karataev · Accepted Answer · 2020-05-03 16:51:52Z

1

Changing the constructor implementation this way should work:

class devices extends Array<device> {
    constructor(items?:Array<device>) {
        super();

        if (items) {
            this.push(...items);
        }
    }

    getDeviceByUid(uid: number): device {
        return this.filter(elmt => elmt.uid == uid)[0];
    }
}

answered May 3, 2020 at 16:51

Eugene Karataev

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1 Comment

Victor Over a year ago

Thanks, it works, however now I'm getting TypeError: Found non-callable @@iterator when using it in Angular. It seems that Angular passes a number to the constructor when doing some refreshes... I don't understand why

mamichels · Accepted Answer · 2020-05-03 16:47:03Z

1

Guess you now initialize by const arr: devices = new devices([])

answered May 3, 2020 at 16:47

mamichels

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