loopback-graphql-server/src/types/Date/index.js

Add Relay based Apollo Server or GraphQL queries on your Loopback server

const { GraphQLScalarType } = require('graphql');
const { GraphQLError } = require('graphql/error');
const { Kind } = require('graphql/language');

module.exports = new GraphQLScalarType({
  name: 'DateTime',
  serialize(value) {
    if (!(value instanceof Date)) {
      // Is this how you raise a 'field error'?
      throw new Error('Field error: value is not an instance of Date');
    }
    if (isNaN(value.getTime())) {
      throw new Error('Field error: value is an invalid Date');
    }
    return value.toJSON();
  },
  parseValue(value) {
    const date = new Date(value);
    if (isNaN(date.getTime())) {
      throw new Error('Field error: value is an invalid Date');
    }
    return date;
  },
  parseLiteral(ast) {
    if (ast.kind !== Kind.STRING) {
      throw new GraphQLError(`Query error: Can only parse strings to dates but got a: ${ast.kind}`, [ast]);
    }
    const result = new Date(ast.value);
    if (isNaN(result.getTime())) {
      throw new GraphQLError('Query error: Invalid date', [ast]);
    }
    if (ast.value !== result.toJSON()) {
      throw new GraphQLError('Query error: Invalid date format, only accepts: YYYY-MM-DDTHH:MM:SS.SSSZ', [ast]);
    }
    return result;
  }
});