How to define GraphQL custom scalars - https://atheros.ai/blog/how-to-design-graphql-custom-scalars

task_type.ts

import {
  GraphQLString,
  GraphQLID,
  GraphQLObjectType,
  GraphQLNonNull,
  GraphQLInt,
  GraphQLFloat,
  GraphQLBoolean,
} from 'graphql';
import DateTime from '../custom-scalars/DateTime';
import TaskStateEnumType from './TaskStateEnumType';
const TaskType = new GraphQLObjectType({
  name: 'Task',
  fields: () => ({
    id: {
      type: new GraphQLNonNull(GraphQLID),
    },
    name: {
      type: new GraphQLNonNull(GraphQLString),
    },
    completed: {
      type: new GraphQLNonNull(GraphQLBoolean),
      defaultValue: false
    },
    state: {
      type: new GraphQLNonNull(TaskStateEnumType),
    },
    progress: {
      type: new GraphQLNonNull(GraphQLFloat),
    },
    taskPriority: {
      type: new GraphQLNonNull(GraphQLInt),
    },
    dueDate: {
      type: DateTime,
    },
    createdAt: {
      type: new GraphQLNonNull(DateTime),
    },
    updatedAt: {
      type: DateTime,
    },
  }),
});
export default TaskType