Building a GraphQL API with Deno and gql

In this blog tutorial, I will demonstrate how to set up a GraphQL server in Deno with gql, a framework-agnostic GraphQL middleware.

# GraphQL Schema

We’ll start with declaring a schema using type definitions and resolvers using graphql_tag and graphql_tools Deno modules, similar to how you do it with Apollo Server or GraphQL Yoga:

import { gql } from 'https://deno.land/x/graphql_tag/mod.ts'
import { makeExecutableSchema } from 'npm:@graphql-tools/schema@10.0.3'

const typeDefs = gql`
  type Query {
    hello: String
  }
`

const resolvers = {
  Query: {
    hello: () => `Hello World!`,
  },
}

const schema = makeExecutableSchema({ resolvers, typeDefs })

Now we have an executable schema that can be passed to a GraphQL server.

# Server setup

In order to setup gql you just need to pass a req object to it so it can read request body and properties.

import { GraphQLHTTP } from 'https://deno.land/x/gql/mod.ts'

// schema code

Deno.serve({
  port: 3000,
  onListen({ hostname, port }) {
    console.log(`☁  Started on http://${hostname}:${port}`)
  },
}, async (req) => {
  const { pathname } = new URL(req.url)
  return pathname === '/graphql'
    ? await GraphQLHTTP<Request>({
      schema,
      graphiql: true,
    })(req)
    : new Response('Not Found', { status: 404 })
})

Now run the server with these permissions (for reading body and using network):

deno run --allow-net --allow-read server.ts

# GraphQL Playground

With server set up and graphiql enabled, the GraphQL Playground will launch as well.

Open your browser on http://localhost:3000 and you will see this:

# Conclusion

This is how you can set up a simple GraphQL server for Deno without any backend frameworks. There are a few examples of using gql with other frameworks, check them out.