index.js

#!/usr/bin/env node

const express = require('express')
const graphqlHTTP = require('express-graphql')
const { buildSchema } = require('graphql')

const gql = `
  type Message {
    id: Int!
    text: String!
  }
  type User {
    id: Int!
    name: String!
    getMessages(limit: Int): [Message]
  }
  type Query {
    listUsers(limit: Int): [User]
  }
`
const schema = buildSchema(gql)

const root = {
  listUsers(params) {
    // You can use params.limit
    // You can return a promise
    return [
      {
        id: 1,
        name: 'user1',
        getMessages(params) {
          // You can use params.limit
          // You can return a promise
          return [
            {
              id: 1,
              text: 'message 1'
            }
          ]
        }
      }
    ]
  }
}

var app = express()
app.use(
  '/graphql',
  graphqlHTTP({
    schema: schema,
    rootValue: root,
    graphiql: true
  })
)

app.listen(4000, () => console.log('Now browse to localhost:4000/graphql'))

package.json

{
  "name": "graphql-example",
  "version": "0.1.0",
  "description": "A simple GraphQL example",
  "main": "index.js",
  "scripts": {
    "dev": "nodemon index.js",
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "Alberto Gimeno <gimenete@gimenete.net>",
  "license": "MIT",
  "bin": "./index.js",
  "dependencies": {
    "express": "^4.14.0",
    "express-graphql": "^0.5.4",
    "graphql": "^0.7.1"
  },
  "devDependencies": {
    "nodemon": "^1.11.0"
  }
}