What steps do I need to follow to write this function in TypeScript?

I am encountering a problem when building the project where it shows errors in 2 functions. Can someone please assist me?

The first error message is as follows:

Argument of type 'IFilmCard[] | undefined' is not assignable to parameter of type 'IFilmCard[]'.
  Type 'undefined' is not assignable to type 'IFilmCard[]'
 
export function __filterFilms(crts: [string, string?], arr: IFilmCard[]) {
    return __filterByGenre(crts[0], __filterByYear(crts[1], arr))
} 

The second error message is as follows:

Argument of type 'IPersonCard[] | undefined' is not assignable to parameter of type 'IPersonCard[]'.Type 'undefined' is not assignable to type 'IPersonCard[]'


export function __filterPersons(crts: [string, string?], arr: IPersonCard[]) {
    return __filterByCountry(crts[0], __filterByYearsPersons(crts[1], arr))
} 

Answer №1

In case your variable is of type IPersonCard[] and if it does not allow being undefined, you may consider appending 'as IPersonCard[]' after assigning the value. However, this approach will result in losing the advantages of TypeScript's type checking functionality. The error indicates that the data could potentially be an IPersonCard[], but there is also a possibility for it to be undefined as well, which was not handled in the code.

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