TypeScript enum-like objects and util functions

ts_enum_objects.ts

// utils

type EnumValue<T> = T[keyof T];
type EnumKey<T> = keyof T;

export function isEnumValue<T extends Record<string, unknown>>(
  enm: T,
  value: unknown
): value is EnumValue<T> {
  return Object.values(enm).includes(value as any);
}

export function assertEnumValue<T extends Record<string, string | number>>(
  enumObj: T,
  value: unknown
): asserts value is EnumValue<T> {
  if (!isEnumValue(enumObj, value)) {
    const values = Object.values(enumObj)
      .map((x) => JSON.stringify(x))
      .join();
    throw new Error(`Not an enum value: ${value}. Expected one of ${values}.`);
  }
}

export function isEnumKey<T extends Record<string, unknown>>(
  enm: T,
  key: unknown
): key is EnumKey<T> {
  return Object.keys(enm).includes(key as any);
}

export function assertEnumKey<T extends Record<string, string | number>>(
  enumObj: T,
  value: unknown
): asserts value is EnumKey<T> {
  if (!isEnumKey(enumObj, value)) {
    const keys = Object.keys(enumObj)
      .map((x) => JSON.stringify(x))
      .join();
    throw new Error(`Not an enum key: ${value}. Expected one of ${keys}.`);
  }
}

// MyEnum

export type MyEnumValue = EnumValue<typeof MyEnum>;
export type MyEnumKey = EnumKey<typeof MyEnum>;
export const MyEnum = {
  KeyA: 1,
  KeyB: 2,
} as const;