Empty checking with type guard

isEmpty.ts

import { isNull } from 'util'

type Empty = null | undefined | 0 | false | ''

export function IsEmpty<T>(thing: T | undefined | null | 0 | false | ''): thing is Empty {
  const undefinedOrNull = typeof thing === 'undefined' || thing === null

  if (undefinedOrNull) {
    return true
  }

  if (typeof thing === 'string' && thing.length === 0) {
    return true
  }

  if (typeof thing === 'number') {
    return thing === 0 || isNaN(thing)
  }

  if (typeof thing === 'boolean') {
    return !thing
  }
  return false || isNull(thing)
}