5-java-script-practices-that-will-help-your-teammates-sleep-at-night_3.ts

type ReferenceString = string

type Obj = Record<string, any>

interface TransformFunc {
  (
    transformer: <V>(value: ReferenceString | Obj | any[]) => V,
    ...args: any
  ): any[]
}

const transform: TransformFunc = (transformer, ...args) => {
  return args.reduce(
    (arr, arg) =>
      Array.isArray(arg)
        ? arr.concat(...arg.map((val) => transformer(val)))
        : transformer(arg),
    [],
  )
}