Arktype Utils

ArkType is a TypeScript validator that delivers highly optimized validators.

I created some wrappers around ArkType's validators.

This is still an early version, the shape might change. I will attempt to keep a nice deprecation path.

Turning FormData into an object

This is a helper method, primarily for Node-based backends that need to turn FormData values into a JS object.

NOTE: This does no validation, it just turns the values into an object

import { formDataToObject } from '@jhecht/arktype-utils';

const fd = new FormData();
fd.append('name', 'Bob');
fd.append('surname', 'Surbob');
fd.append('age', '31');

const obj = formDataToObject(fd);

For repeated entries, if there is more than 1 value found, it will be turned into an array

import { formDataToObject } from '@jhecht/arktype-utils';
const fd = new FormData();
fd.append('name', 'Bob');
fd.append('name', 'John');

const obj = formDataToObject(fd);

// { name: ['Bob', 'John']}
console.info(obj);

This method all does it's best guess for JSON-parsible values, including BigInt

import { formDataToObject } from '@jhecht/arktype-utils';

const fd = new FormData();
fd.append('number', '13');
fd.append('otherNumber', '3.1415');
fd.append('bigNumber', '300n');

const obj = formDataToObject(fd);

// { number: 13, otherNumber: 3.1415, bigNumber: 300n } -- no strings!
console.info(obj);

You can also for an element to always be an array by ending it with []:

import { formDataToObject } from '@jhecht/arktype-utils';

const fd = new FormData();
fd.append('email[]', '[email protected]');

const obj = formDataToObject(fd);

// { email: ['[email protected]'] }
console.info(obj);

You can also specify a nested key value, turning the result into either an object or an array depending on whether or not those keys are numerical.

import { formDataToObject } from '@jhecht/artktype-utils';

const fd = new FormData();
fd.append('obj[id]', 'uuid');
fd.append('obj[name]', "J'onn");
fd.append('obj[age]', '307');

const obj = formDataToObject(fd);
/**
 * {
 *  obj: {
 *    id: 'uuid',
 *    name: 'J\'onn',
 *    age: 307,
 *  }
 * }
 */
console.info(obj);

import { formDataToObject } from '@jhecht/artktype-utils';

const fd = new FormData();
fd.append('name[0]', 'Bruce');
fd.append('name[1]', 'Clark');
fd.append('name[3]', 'Barry');
fd.append('name[2]', "J'onn");

const obj = formDataToObject(fd);

/**
 * {
 *  name: ['Bruce', 'Clark', 'J\'onn', 'Barry']
 * }
 */
console.info(obj);

Deeply Nested Objects and Arrays

formDataToObject supports advanced dot and bracket notation for deeply nested structures, including arrays of objects and nested arrays:

const fd = new FormData();
fd.append('payments.id1.location', 'England');
fd.append('payments.id1.age', '37');
fd.append('payments.id2.location', 'New York');
fd.append('payments.id2.age', '81');
fd.append('payments.id2.name', 'Steve');

const obj = formDataToObject(fd);
// {
//   payments: {
//     id1: { location: 'England', age: 37 },
//     id2: { location: 'New York', age: 81, name: 'Steve' },
//   }
// }

const fd2 = new FormData();
fd2.append('locations[].name', 'England');
fd2.append('locations[].members[]', 'John');
fd2.append('locations[].members[]', 'Joe');
fd2.append('locations[].name', 'France');
fd2.append('locations[].members[]', 'Francis');
fd2.append('locations[].members[]', 'Joe2');

const obj2 = formDataToObject(fd2);
// {
//   locations: [
//     { name: 'England', members: ['John', 'Joe'] },
//     { name: 'France', members: ['Francis', 'Joe2'] }
//   ]
// }

Validating Data with ArkType

I created this wrapper, which throws if there are any error values. It takes two arguments, one being a FormData object, and the other a type or scope call from ArkType, which serves as the validator for the object-ified FormData.

import { validateFormData } from '@jhecht/arktype-utils';
import { type } from 'arktype';

const fd = new FormData();
// Assume `fd` is gotten from the request body here

try {
  const obj = validateFormData(
    fd,
    type({
      name: 'string>=2',
      age: '13<=number',
      favoriteMovies: 'string[]',
    }),
  );
  // If this code is ran we know that the value of the `fd` variables passes the above validations when turned into an object
  console.info(obj);
} catch (e) {
  // If we end up here, `e` will be the `Problems` object returned by ArkType's validator
  console.error(e);
}