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How to deal with Date Types in NextJS getStaticProps

January 19, 2021

If you’re using NextJS you’re probably using the getStaticProps function or the getServerSideProps function on your pages to fetch data to populate your page props. Something I discovered the other day is that you can’t pass some types in your props object to your React component including the Date type. In my particular application I’m using Prisma to get objects from my database that include createdAt and updatedAt dates.

My code looks a little something like this:

export const getStaticProps: GetStaticProps = async () => {
  const users = await prisma.user.findMany();
  return { props: { users }, revalidate: 1 };
};

However, this was a problem because getStaticProps serializes the returned object and Date (along with a few other types) can’t be serialized. You’ll get an error like ("[object Date]") cannot be serialized as JSON. Please only return JSON serializable data type. So I found this discussion on the topic https://github.com/vercel/next.js/discussions/11498. I ended up installing a package called babel-plugin-superjson-next and superjson and added a .babelrc file with these contents:

{
  "presets": ["next/babel"],
  "plugins": ["superjson-next"]
}

This just fixes the issue as described in their docs: https://github.com/blitz-js/superjson#using-with-nextjs.

Should also note here you could fix this by manually handling each Date type in your getStaticProps method. You could map over each returned object and convert the Date to a string before returning that array.