Real world use case for .filter(Boolean) by @DoctorDerek https://medium.com/p/87b5112f9f6d

[path]\[slug].tsx

export async function getStaticPaths() {
  // search 1 level recursively in @/data/
  const dataRegExpMarkdown = /(.+)?\\(.+)?\\(.+)?\.md/
  // ["data\\hosting\\packages.md", "data", "hosting", "packages"]
  const paths: any[] = getFilesRecursively("data")
    .map((path: string) => dataRegExpMarkdown.exec(path))
    .filter((item: any[]) => Boolean(item)) // remove falsy
    .map((item: any[]) => ({
      params: {
        path: item[2], // "hosting" (supports 1 directory)
        slug: item[3], // "packages" (excluding .md or .mdx)
      },
    }))
  return {
    paths: paths,
    fallback: false,
  }
}