filterEnum in typescript

filterEnum.ts

/**
 * Filters am emum to only return the keys represented in it
 *
 * How is this not built into the language?
 * https://stackoverflow.com/a/21294925/511710
 * https://noahbass.com/posts/typescript-enum-iteration
 *
 * @param {{}} e
 * @returns
 */
function filterEnum(e: {}) {
  return Object.keys(e).filter(v => isNaN(Number(v)));
}