import { isRFC3339 } from 'validator';
import { GraphQLScalarType } from 'graphql';

export default new GraphQLScalarType({
  name: 'Timestamp',
  description: 'RFC3339 Timestamp format',
  serialize(value) {
    if (isRFC3339(value)) {
      return value;
    }
    throw new Error('Timestamp cannot represent an invalid RFC-3339 Timestamp string');
  },
  parseValue(value) {
    if (isRFC3339(value)) {
      return value;
    }
    throw new Error('Timestamp cannot represent an invalid RFC-3339 Timestamp string');
  },
  parseLiteral(ast) {
    if (isRFC3339(ast.value)) {
      return ast.value;
    }
    throw new Error('Timestamp cannot represent an invalid RFC-3339 Timestamp string');
  }
});

scalar Timestamp

import timeStamp from './scalars/timeStamp';
.
.
.
.
const schema = {
  typeDefs: [
    myTypeDefs
  ],
  resolvers: merge(
    resolvers,
    timeStamp
  ),
};

export default makeExecutableSchema({
  typeDefs: schema.typeDefs,
  resolvers: schema.resolvers
});

throw new _1.SchemaError(""" + typeName + "" defined in resolvers, but has invalid value "" + resolverValue + "". A resolver's value " +
            ^

Error: "name" defined in resolvers, but has invalid value "Timestamp". A resolver's value must be of type object or function.