graphql directive

graphqlDirective.js

const {makeExecutableSchema} = require('graphql-tools');
const {graphql} = require('graphql');

// Construct a schema, using GraphQL schema language
const typeDefs = `
  directive @upper on FIELD_DEFINITION

  type Query {
    hello: String @upper
  }
`;

// Implement resolvers for out custom Directive
const directiveResolvers = {
    upper(
        next,
        src,
        args,
        context,
    ) {
        return next().then((str) => {
            if (typeof(str) === 'string') {
                return str.toUpperCase();
            }
            return str;
        });
    },
}

// Provide resolver functions for your schema fields
const resolvers = {
    Query: {
        hello: (root, args, context) => {
            return 'Hello world!';
        },
    },
};

export const schema = makeExecutableSchema({
    typeDefs,
    resolvers,
    directiveResolvers,
});

const query = `
query UPPER_HELLO {
  hello
}
`;

graphql(schema, query).then((result) => console.log('Got result', result));