@conform-to/validitystate

@conform-to/validitystate

The current version is not compatible with conform react adapter.

Conform helpers for server validation based on the validation attributes.

API Reference

• parse
• validate
• defaultFormatError
• getError

parse

A function to parse FormData or URLSearchParams on the server based on the constraints and an optional error formatter.

import { type FormConstraints, type FormatErrorArgs, parse } from '@conform-to/validitystate';

const constraints = {
    email: { type: 'email', required: true },
    password: { type: 'password', required: true },
    remember: { type: 'checkbox' },
} satisify FormConstraints;

function formatError({ input }: FormatErrorArgs) {
    switch (input.name) {
        case 'email': {
            if (input.validity.valueMissing) {
                return 'Email is required';
            } else if (input.validity.typeMismatch) {
                return 'Email is invalid';
            }
            break;
        }
        case 'password': {
            if (input.validity.valueMissing) {
                return 'Password is required';
            }
            break;
        }
     }

     return '';
}

const submission = parse(formData, {
  constraints,
  formatError,
});

// The error will be a dictinioary mapping input name to the corresponding errors
// e.g. { email: 'Email is required', password: 'Password is required' }
console.log(submission.error);

if (!submission.error) {
    // If no error, the parsed data will be available with the inferred type.
    // e.g. { email: string; password: string; remember: boolean; }
    console.log(submission.value);
}

The error formatter can also return multiple error.

function formatError({ input }: FormatErrorArgs) {
  const error = [];

  switch (input.name) {
    case 'email': {
      if (input.validity.valueMissing) {
        error.push('Email is required');
      }
      if (input.validity.typeMismatch) {
        error.push('Email is invalid');
      }
      break;
    }
    case 'password': {
      if (input.validity.valueMissing) {
        error.push('Password is required');
      }
      if (input.validity.tooShort) {
        error.push('Passowrd is too short');
      }
      break;
    }
  }

  return error;
}

If no error formatter is provided, check the defaultFormatError helpers for the default behavior.

validate

A helper to customize client validation by reusing the constraints and error formatter. Error will be set on the form control element using the setCustomValidity method. It should be called before reporting new error (i.e. triggering form.reportValidity()).

import { validate } from '@conform-to/validitystate';

function Example() {
  return (
    <form
      onSubmit={(event) => {
        const form = event.currentTarget;

        // validate before reporting new error
        validate(form, {
          constraints,
          formatError,
        });

        if (!form.reportValidity()) {
          event.preventDefault();
        }
      }}
      noValidate
    >
      {/* ... */}
    </form>
  );
}

defaultFormatError

This is the default error formatter used by parse to represent error by all failed validation attributes. For example:

{ "email": ["required", "type"], "password": ["required"] }

This helper is useful if you want to customize the error based on the default error formatter.

import { type FormConstraints, type FormatErrorArgs, defaultFormatError } from '@conform-to/validitystate';

const constraints = {
    email: { type: 'email', required: true },
    password: { type: 'password', required: true },
    confirmPassowrd: { type: 'password', required: true },
} satisify FormConstraints;

function formatError({ input }: FormatErrorArgs<typeof constraints>) {
    const error = defaultFormatError({ input });

    if (input.name === 'confirmPassword' && error.length === 0 && value.password !== value.confirmPassword) {
        error.push('notmatch');
    }

    return error;
}

const submission = parse(formData, {
    constraints,
    formatError,
});

getError

It gets the actual error messages stored on the validationMessage property. This is needed if the custom error formatter returns multiple error.

import { getError } from '@conform-to/validitystate';

function Example() {
  const [error, setError] = useState({});

  return (
    <form
      onInvalid={(event) => {
        const input = event.target as HTMLInputElement;

        setError((prev) => ({
          ...prev,
          [input.name]: getError(input.validationMessage),
        }));

        event.preventDefault();
      }}
    >
      {/* ... */}
    </form>
  );
}

Attributes supported

month and week input type are not implemented due to limited browser support

Support	type	required	minLength	maxLength	pattern	min	max	step	multiple
text		🗸	🗸	🗸	🗸
email	🗸	🗸	🗸	🗸	🗸
password		🗸	🗸	🗸	🗸
url	🗸	🗸	🗸	🗸	🗸
tel		🗸	🗸	🗸	🗸
search		🗸	🗸	🗸	🗸
datetime-local		🗸				🗸	🗸	🗸
date		🗸				🗸	🗸	🗸
time		🗸				🗸	🗸	🗸
select		🗸							🗸
textarea		🗸	🗸	🗸
radio		🗸
color		🗸
checkbox		🗸
number		🗸				🗸	🗸	🗸
range		🗸				🗸	🗸	🗸
file		🗸							🗸