hello2.js

var express = require('express');
var graphqlHTTP = require('express-graphql');
var Graphql = require('graphql');

const personType = new Graphql.GraphQLObjectType({
  name: "Person",
  fields:{
    name: { type: Graphql.GraphQLString },
    age: { type: Graphql.GraphQLInt }
  }
});

const queryType = new Graphql.GraphQLObjectType({
  name: "Query",
  fields: {
    hello: {
      type: Graphql.GraphQLString,
      resolve: () => 'Hello world!',
    },
    persons: {
      type: new Graphql.GraphQLList(personType),
      args: {
        name: {type: Graphql.GraphQLString},
        age: {type: Graphql.GraphQLInt}
      },
      resolve: (post, args, context, info) => {
        console.log(context);
        console.log(args);
        const {name, age} = args;

        return [
          {name:"kim", age: 20},
          {name:"lee", age: 30},
          {name:"park", age: 40},
        ].filter((person) => {
          if(!name && !age){ return true; }
          if(!age && name && person.name === name){ return true; }
          if(!name && age && person.age === age){ return true; }
          if(name && age && person.name === name && person.age === age){ return true; }
          return false;
        });
      }
    }
  }
});

const schema = new Graphql.GraphQLSchema({query: queryType});

var app = express();
const session = {id: "1001", expires: 20000};

app.use('/graphql', graphqlHTTP({
  schema: schema,
  graphiql: true,
  context: session,
}));
app.listen(4000, () => console.log('Now browse to localhost:4000/graphql'));