graphql-playground/server/schema/schema.js

const graphql = require('graphql');
const _ = require('lodash');

const {
  GraphQLObjectType,
  GraphQLString,
  GraphQLSchema
} = graphql;

// temp data
const books = [
  { name: 'Name of the Wind', genre: 'Fantasy', id: '1' },
  { name: 'The Final Empire', genre: 'Fantasy', id: '2' },
  { name: 'The Long Earth', genre: 'Sci-Fi', id: '3' }
];

const BookType = new GraphQLObjectType({
  name: 'Book',
  fields: () => ({
    id: { type: GraphQLString },
    name: { type: GraphQLString },
    genre: { type: GraphQLString }
  })
});

const RootQuery = new GraphQLObjectType({
  name: 'RootQueryType',
  fields: {
    book: {
      type: BookType,
      args: { id: { type: GraphQLString } },
      resolve (parent, { id }) {
        return _.find(books, { id });
      }
    }
  }
});

module.exports = new GraphQLSchema({
  query: RootQuery
});