Next.js Absolute API URL Helper

This package provides a quick solution around the common Next.js error that happens while trying to fetch data in the server side without providing a full url:

Server Error: Only absolute URLs are supported

Why does this happen though? Since these data fetching functions run only on the server, they have no way of knowing the origin like code on the client side does, so Next.js reminds you that an absolute URL has to be provided.

Warning: this helper only works for getServerSideProps and getInitialProps (both client and server) -- For getStaticProps you should either hard code the URL or use enviroment variables.

Usage

Simply provide the context to the function:

import apiUrl from "next-api-url";

fetch(`${apiUrl(ctx)}/posts`); // http://localhost:3000/api
fetch(`${apiUrl(ctx)}/posts`); // https://blog.com/api
fetch(`${apiUrl({ req: ctx.req })}/posts`); // https://blog.com/api
fetch(`${apiUrl({ req: ctx.req })}/posts`, false); // https://blog.com

Examples

getServerSideProps

import apiUrl from "next-api-url";

export const getServerSideProps: GetServerSideProps = async (context) => {
  const posts = await (await fetch(`${apiUrl(context)}/api/posts`)).json();

  return {
    props: { posts },
  };
};

getInitialProps (works on server and client 😊)

import apiUrl from "next-api-url";

Page.getInitialProps = async (context) => {
  const posts = await (await fetch(`${apiUrl(context)}/api/posts`)).json();

  return {
    posts,
  };
};

getServerSideProps using wrapper

import { withApiUrl } from "next-api-url";

export const getServerSideProps = withApiUrl(async (context, url) => {
  const posts = await (await fetch(`${url}/api/posts`)).json();

  return {
    props: {
      posts,
    },
  };
});

getInitialProps using wrapper

import { withApiUrl } from "next-api-url";

Page.getInitialProps = withApiUrl(async (context, url) => {
  const posts = await (await fetch(`${url}/api/posts`)).json();

  return {
    posts,
  };
});