TypeScript Question

enum-in-array.tsx

// when T is a custom type we want to infer from 
// that rather than extending from any string 
export function isValueInArray<T extends string>(
  values: T[],
  value: T | undefined
) {
  return value ? values.includes(value) : false;
}

type Status = 'PENDING' | 'ERROR' | 'SUCCESS';

type Props = {
  status: Status;
};

function Component(props: Props) {
  // this should throw a type erorr because "TEST" isn’t a valid Status
  // the reason it works is because isValueInArray<T extends string>
  // so any string is valid
  const isValidValue = isValueInArray(['PENDING', 'TEST'], props.status);

  return isValidValue ? <div>Valid</div> : <div>Invalid</div>;
}