Applying Middleware to Apollo Server

apollo-middleware.js

const { ApolloServer, gql, makeExecutableSchema } = require('apollo-server')
const { applyMiddleware } = require('graphql-middleware')

const uppercaseCategory = async (resolve, parent, args, context, info) => {
  const result = await resolve(parent, args, context, info)

  return result.toUpperCase()
}

const postsMiddleware = async (resolve, parent, args, context, info) => {
  const result = await resolve(parent, args, context, info)

  const formattedPosts = result.reduce(
    (formatted, post) => [
      ...formatted,
      {
        ...post,
        title: `${post.category}: ${post.title}`
      }
    ],
    []
  )

  return formattedPosts
}

const postMiddleware = {
  Post: {
    category: uppercaseCategory
  },
  Query: {
    posts: postsMiddleware
  }
}

const middleware = [postMiddleware]

const schemaWithMiddleware = applyMiddleware(schema, ...middleware)

const server = new ApolloServer({ schema: schemaWithMiddleware })