jotai-form

👻📃

Tweets

• Initial announcement
• Example with Joi

TOC

• jotai-form
  • Tweets
  • TOC
  • Install
  • Usage
    • Basic Usage
    • Form Level Validation
    • Form Controls
  • API
  • Primitives
    • atomWithValidate
  • Atom Curator Functions
    • validateAtoms
    • atomWithFormControls
  • Validator Functions

Install

The library can be simply installed by adding jotai-form to your dependencies

npm i jotai-form
# or
yarn add jotai-form
# or
pnpm add jotai-form

Note: The library depends on jotai so please make sure you have jotai installed, if not you can do so by using the below commands

npm i jotai

Usage

Basic Usage

The very basic form of validation and the most common use case will involve using atomWithValidate, which creates a similar atom to jotai

This atom can be used with the useAtom helper but with a slight change. The change is that instead of directly giving you the state value you now have form based properties

const form = {
  value, // the current value of the state
  isDirty, // boolean value based on if the value has changed from the initial value
  isValid, // boolean value representing if the current atom state is valid
  error, // if an error was thrown from the validator, that'll be available here

  // and a conditional
  // boolean value when working with async validation, this
  // will be `true` for the duration of the validation and `false` once the validation is complete
  isValidating,
};

Note: isValidating will not be a property if you are using a synchronous validation function, your IDE should already help you with this but use this property only when using asynchronous validation functions.

An example, combining all that information. You can find more such examples in the examples folder

import { useAtom } from 'jotai';
import { atomWithValidate } from 'jotai-form';
import * as Yup from 'yup';

// defining a validation schema for the atom
const emailSchema = Yup.string().email().required();

// creating the atom with an async validation function
const emailAtom = atomWithValidate('', {
  validate: async (v) => {
    await emailSchema.validate(v);
    return v;
  },
});

const Form = () => {
  // Same API as other jotai atom's with the difference being
  // addition of form properties on `email`
  const [email, setEmail] = useAtom(emailAtom);

  return (
    <div>
      <input value={email.value} onChange={(e) => setEmail(e.target.value)} />
      <span>{email.isValid && 'Valid'}</span>
      <span>{!email.isValid && `${email.error}`}</span>
    </div>
  );
};

Form Level Validation

You might have cases where you would like to validate the combination of multiple values.

Example, Maybe the combined name length of first and last names cannot exceed 15 characters.

For this you can use validateAtoms which takes in a atom group and a validator function which works very similar to the atomWithValidate's validate function.

The atom group validation atom is a read only atom and with similar properties as the atom returned from atomWithValidate. The only change being values instead of value. This contains the passed atom group's values

Note: In most cases the atomWithValidate should suffice, form validation comes into the picture when dealing with fields that do need a final validation, the example here is one of the many cases but do not abuse form level validation.

Note: validateAtoms will not trigger each atom's internal validate functions, while adding disabled states or any other case where you need to check the atom's validity, please use the atom's own isValid and error properties.

import { useAtom } from 'jotai';
import { atomWithValidate, validateAtoms } from 'jotai-form';
import * as Yup from 'yup';

const nameSchema = Yup.string().required();

const firstNameAtom = atomWithValidate('', {
  validate: async (v) => {
    await nameSchema.validate(v);
    return v;
  },
});

const lastNameAtom = atomWithValidate('', {
  validate: async (v) => {
    await nameSchema.validate(v);
    return v;
  },
});

const formGroup = validateAtoms(
  {
    firstName: firstNameAtom,
    lastName: lastNameAtom,
  },
  (values) => {
    if (values.firstName.length + values.lastName.length > 15) {
      throw new Error("Overall name can't be longer than 15 characters");
    }
  },
);

const Form = () => {
  const [firstName, setFirstName] = useAtom(firstNameAtom);
  const [lastName, setLastName] = useAtom(lastNameAtom);
  const [formState] = useAtom(formGroup);

  return (
    <div>
      <label>
        firstName
        <input
          value={firstName.value}
          onChange={(e) => setFirstName(e.target.value)}
        />
        <span>{firstName.isValid && 'Valid'}</span>
        <span>{!firstName.isValid && `${email.error}`}</span>
      </label>

      <label>
        lastName
        <input
          value={lastName.value}
          onChange={(e) => setLastName(e.target.value)}
        />
        <span>{lastName.isValid && 'Valid'}</span>
        <span>{!lastName.isValid && `${email.error}`}</span>
      </label>

      <button
        disabled={!formState.isValid || !firstName.isValid || !lastName.isValid}
      >
        Submit
      </button>
      {
        // or
        // <button disabled={!(formState.isValid && firstName.isValid && lastName.isValid)}>Submit</button>
      }
      <span>{!formState.isValid && `${formState.error}`}</span>
    </div>
  );
};

Form Controls

Added in v0.1.1

Form Group Validation using validateAtoms is easier when the form is tinier and doesn't need much, but having multiple such hooks for a larger group of atoms might not be easy and lead to a lot of hooks.

We would like to keep the atomic approach but in case of forms it does need a little extension and so you can do so with atomWithFormControls.

Here's an example of what an example of this would look like.

Notes

1. atomWithFormControls still expects a atomWithValidate group to be passed to it, this is so that you can still move and combine the same atom with other form control groups if needed.

import { useAtom } from 'jotai';
import { atomWithValidate, validateAtoms } from 'jotai-form';
import * as Yup from 'yup';

const nameSchema = Yup.string().required();

const firstNameAtom = atomWithValidate('', {
  validate: async (v) => {
    await nameSchema.validate(v);
    return v;
  },
});

const lastNameAtom = atomWithValidate('', {
  validate: async (v) => {
    await nameSchema.validate(v);
    return v;
  },
});

const formControlAtom = atomWithFormControls(
  {
    firstName: firstNameAtom,
    lastName: lastNameAtom,
  },
  {
    validate: (values) => {
      if (values.firstName != 'jotai') {
        throw new Error("Oh well, can't let you in");
      }
    },
  },
);

function FormComponent() {
  const {
    // Values per field
    values,
    // is the form valid
    isValid,
    // focused state per field
    focused,
    // touched state per field
    touched,
    // errors per field
    fieldErrors,
    // form error
    error,
    // handle change of value per field
    handleOnChange,
    // handle blur event per field
    handleOnBlur,
    // handle focus event per field
    handleOnFocus,
  } = useAtomValue(formControlAtom);

  return (
    <>
      <form>
        <div>
          <input
            value={values.firstName}
            onChange={(e) => {
              handleOnChange('firstName')(e.target.value);
            }}
            onFocus={handleOnFocus('firstName')}
            onBlur={handleOnBlur('firstName')}
          />
          <p>
            {fieldErrors.firstName && touched.firstName
              ? `${fieldErrors.firstName}`
              : 'Valid'}
          </p>
        </div>
        <div>
          <input
            value={values.lastName}
            onChange={(e) => {
              handleOnChange('lastName')(e.target.value);
            }}
            onFocus={handleOnFocus('lastName')}
            onBlur={handleOnBlur('lastName')}
          />
          <p>
            {fieldErrors.firstName && touched.firstName
              ? `${fieldErrors.firstName}`
              : 'Valid'}
          </p>
        </div>
        <p>isValid: {isValid ? 'Valid' : "Something's wrong"}</p>
        <p>Form Error: {error?.toString()}</p>
      </form>
    </>
  );
}

API

Primitives

atomWithValidate

atomWithValidate is the primary base for create validating atoms and it's state and validations are inferred by the other atoms in most cases.

atomWithValidate(initialValue, options);

Atom Curator Functions

validateAtoms

The validateAtoms function accepts a group of primitives, in this case atomWithValidate and a validator function for the entire group

validateAtoms(atomGroup, validator);

atomWithFormControls

atomWithFormControls(atomGroup, options);

Validator Functions

While the API for the validator functions, options.validate or validator are very similar there's a few differences and also let's talk about how they work and what's the different

Rules

Things that apply to all the validator functions

1. If the function executes without any error, the validation was successful.
2. If there's any error , even something raised from an inner function, it'll make the form invalid.
3. Can pass in a async / sync function for validation.
4. The function will be passed the value of the atom that they are supposed to validate. options.validate from atomWithValidate will get the value for it's own atom and validator, options.validate for validateAtoms and atomWithFormControls will get all the values from the passed in atomGroup)

Differences

1. Primitive atoms expects you to return the value at the end of the validation to make sure the validation was run for the same value and your state and validated state doesn't have any mismatch.

2. Curator Functions doesn't expect a return value since it acts as a listener to the group of atoms passed in and the values will not need the same state check, so you can just throw errors from it and if it doesn't return the values back there won't be a problem

Note: The keys of the object defined for the atomGroup is used as the keys for the values that are passed to the atom curator functions, the same is applicable for atomWithFormControls

const atomGroup = { name: nameAtom, age: ageAtom };
const validator = (values) => {
  values.name; // nameAtom's value
  values.age; // ageAtom's value
};
validateAtoms(atomGroup, validator);

atomWithFormControls(atomGroup, {
  validate: validator,
});