Add fetchJSON utility, based on best-practices from Vercel (SWR offic…

…ial recommendations) for server-side fetching

src/utils/api/fetchJSON.ts

@@ -0,0 +1,25 @@
+/**
+ * Uses built-in Next.js "fetch" lib and attempt to transform response as JSON
+ *
+ * Meant to be used from the server side.
+ * Fetching from the client side should rather use SWR hook.
+ *
+ * @example Server-side use "fetchJSON"
+ * @see https://github.com/vercel/swr/blob/master/examples/server-render/pages/%5Bpokemon%5D.js#L40
+ *
+ * @example Client-side use "useSWR" with "initialData" pre-fetched from getServerSideProps
+ * @see https://github.com/vercel/swr/blob/master/examples/server-render/pages/%5Bpokemon%5D.js#L9
+ *
+ * @param args
+ * @see https://nextjs.org/blog/next-9-4#improved-built-in-fetch-support
+ */
+const fetchJSON: <JSON = any>(
+  input: RequestInfo,
+  init?: RequestInit,
+) => Promise<JSON> = async (...args) => {
+  const res = await fetch(...args);
+  if (!res.ok) throw new Error(res.statusText);
+  return res.json();
+};
+
+export default fetchJSON;