Interoperation between constant arrays and type definitions in TypeScript

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Interoperation between constant arrays and type definitions in TypeScript

export const keyArray = ["key1", "key2", "key3"] as const;

export type Key = typeof keyArray[number];

export function isKey(value: string): value is Key {
  return (keyArray as readonly string[]).includes(value);
}

export function isKeys(values: string[]): values is Key[] {
  return values.every((key) => isKey(key));
}