Singleton helper for next.js

README.md

Synchronous

const prisma = singletonSync('prisma', () => {
  return new PrismaClient()
})

Asynchronous

const apolloServer = await singleton("apolloServer", async () => {
  const schema = await buildSchema({
    resolvers: [...],
  });

  return new ApolloServer({
    schema,
  });
});

singleton.ts

export const singleton = async <T>(id: string, fn: () => Promise<T>) => {
  if (process.env.NODE_ENV === "production") {
    return await fn()
  } else {
    if (!global[id]) {
      global[id] = await fn()
    }
    return global[id] as T;
  }
};


export const singletonSync = <T>(id: string, fn: () => T) => {
  if (process.env.NODE_ENV === "production") {
    return fn();
  } else {
    if (!global[id]) {
      global[id] = fn();
    }
    return global[id] as T;
  }
};