index.js

// Import the required libraries
var graphql = require('graphql');
var graphqlHTTP = require('express-graphql');
var express = require('express');

// Import the data you created above
var data = require('./data.json');

// Define the User type with two string fields: `id` and `name`.
// The type of User is GraphQLObjectType, which has child fields
// with their own types (in this case, GraphQLString).
var userType = new graphql.GraphQLObjectType({
  name: 'User',
  fields: {
    id: { type: graphql.GraphQLString },
    name: { type: graphql.GraphQLString },
  }
});

// Define the schema with one top-level field, `user`, that
// takes an `id` argument and returns the User with that ID.
// Note that the `query` is a GraphQLObjectType, just like User.
// The `user` field, however, is a userType, which we defined above.
var schema = new graphql.GraphQLSchema({
  query: new graphql.GraphQLObjectType({
    name: 'Query',
    fields: {
      user: {
        type: userType,
        // `args` describes the arguments that the `user` query accepts
        args: {
          id: { type: graphql.GraphQLString }
        },
        // The resolve function describes how to "resolve" or fulfill
        // the incoming query.
        // In this case we use the `id` argument from above as a key
        // to get the User from `data`
        resolve: function (_, args) {
          return data[args.id];
        }
      }
    }
  })
});

express()
  .use('/graphql', graphqlHTTP({ schema: schema, pretty: true }))
  .listen(3000);

console.log('GraphQL server running on http://localhost:3000/graphql');