Element implicitly has an 'any' type because index expression is not of type 'number'

Question

I get error below. I know what this code means but I do not know how interface should look like:

Element implicitly has an 'any' type because index expression is not of type 'number'.

interfaces:

export declare interface Category {
    id: string;
    name: string;
    parent_id: string;
}

export declare interface CategoriesMap {
    [key: string]: Category;
}

component:

private listOfSubcategories: CategoriesMap[] = [];

private selectCategory($event: any, index: string) {
        this.category = this.listOfSubcategories[index][$event.target.value];
    }

Regards

Answer 1

Your this.listOfSubcategories is an array, but index is a string. This should be a number to read from the array.