The Typescript error "Attempting to call a function that does not have any callable signatures.(2349)"

Could you please assist me in resolving this issue:

type IValidator = (value?: string) => string | undefined;
type IComposeValidators = (validators: ((value?: string) => string | undefined)[]) => IValidator;

export const composeValidators: IComposeValidators = (...validators) => (value) => {
  return validators.reduce((error, validator) => error || validator(value), undefined); // There seems to be an error with this expression. Type '((value?: string | undefined) => string | undefined)[]' lacks call signatures.(2349)
};

Typescript Playground

Answer №1

I discovered a resolution:

interface ValidatorFn {
  (value?: string): string | undefined;
}

export const combineValidators = (...validators: ValidatorFn[]): ValidatorFn => (value) => {
  return validators.reduce((error: string | undefined, validator) => error || validator(value), undefined);
};

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