react-use-form-state

Motivation

Managing form state in React can be a bit unwieldy sometimes. There are plenty of great solutions already available that make managing forms state a breeze. However, many of those solutions are opinionated, packed with tons of features that may end up not being used, and/or require shipping a few extra bytes!

Luckily, the recent introduction of React Hooks and the ability to write custom hooks have enabled new possibilities when it comes sharing state logic. Form state is no exception!

react-use-form-state is a small React Hook that attempts to simplify managing form state, using the native form input elements you are familiar with!

Getting Started

To get it started, add react-use-form-state to your project:

npm install --save react-use-form-state

Please note that react-use-form-state requires react@^16.8.0 as a peer dependency.

Examples

Basic Usage

import { useFormState } from 'react-use-form-state';

export default function SignUpForm({ onSubmit }) {
  const [formState, { text, email, password, radio }] = useFormState();

  function handleSubmit(e) {
    // ...
  }

  return (
    <form onSubmit={handleSubmit}>
      <input {...text('name')} />
      <input {...email('email')} required />
      <input {...password('password')} required minLength="8" />
      <input {...radio('plan', 'free')} />
      <input {...radio('plan', 'premium')} />
    </form>
  );
}

From the example above, as the user fills in the form, the formState object will look something like this:

{
  values: {
    name: 'Mary Poppins',
    email: '[email protected]',
    password: '1234',
    plan: 'free',
  },
  touched: {
    name: true,
    email: true,
    password: true,
    plan: true,
  },
  validity: {
    name: true,
    email: true,
    password: false,
    plan: true,
  },
  errors: {
    password: 'Please lengthen this text to 8 characters or more',
  },
  clear: Function,
  clearField: Function,
  reset: Function,
  resetField: Function,
  setField: Function,
}

Initial State

useFormState takes an initial state object with keys matching the names of the inputs.

export default function RentCarForm() {
  const [formState, { checkbox, radio, select }] = useFormState({
    trip: 'roundtrip',
    type: ['sedan', 'suv', 'van'],
  });
  return (
    <form>
      <select {...select('trip')}>
        <option value="roundtrip">Same Drop-off</option>
        <option value="oneway">Different Drop-off</option>
      </select>
      <input {...checkbox('type', 'sedan')} />
      <input {...checkbox('type', 'suv')} />
      <input {...checkbox('type', 'van')} />
      <button>Submit</button>
    </form>
  );
}

Global Handlers

useFormState supports a variety of form-level event handlers that you could use to perform certain actions:

export default function RentCarForm() {
  const [formState, { email, password }] = useFormState(null, {
    onChange(e, stateValues, nextStateValues) {
      const { name, value } = e.target;
      console.log(`the ${name} input has changed!`);
    },
  });
  return (
    <>
      <input {...text('username')} />
      <input {...password('password')} />
    </>
  );
}

Advanced Input Options

useFormState provides a quick and simple API to get started with building a form and managing its state. It also supports HTML5 form validation out of the box.

<input {...password('password')} required minLength="8" />

While this covers that majority of validation cases, there are times when you need to attach custom event handlers or perform custom validation.

For this, all input functions provide an alternate API that allows you attach input-level event handlers such as onChange and onBlur, as well as providing custom validation logic.

export default function SignUpForm() {
  const [state, { text, password }] = useFormState();
  return (
    <>
      <input {...text('username')} required />
      <input
        {...password({
          name: 'password',
          onChange: e => console.log('password input changed!'),
          onBlur: e => console.log('password input lost focus!'),
          validate: (value, values, e) => validatePassword(value),
          validateOnBlur: true,
        })}
      />
    </>
  );
}

Custom Input Validation

The example above demonstrates how you can determine the validity of an input by passing a validate() method. You can also specify custom validation errors using the same method.

The input is considered valid if this method returns true or undefined.

Any truthy value other than true returned from this method will make the input invalid. This returned value is used as a custom validation error that can be retrieved from state.errors.

For convenience, empty collection values such as empty objects, empty arrays, empty maps, empty sets are not considered invalidation errors, and if returned the input will be valid.

<input
  {...password({
    name: 'password',

    // can also return objects, arrays, etc, for more complex error objects
    validate: (value, values, event) => {
      if (!value.trim()) {
        return 'Password is required';
      }
      if (!STRONG_PASSWORD_REGEX.test(value)) {
        return 'Password is not strong enough';
      }
    },
  })}
/>

If the input's value is invalid based on the rules specified above, the form state will look similar to this:

{
  validity: {
    password: false,
  },
  errors: {
    password: 'Password is not strong enough',
  }
}

If the validate() method is not specified, useFormState will fallback to the HTML5 constraints validation to determine the validity of the input along with the appropriate error message.

Check If the Form State Is Pristine

useFormState exposes a pristine object, and an isPristine() helper via formState that you can use to check if the user has made any changes.

This can be used for a Submit button, to disable it, if there are no actual changes to the form state:

function PristineForm() {
  const [formState, { text, password }] = useFormState();
  return (
    <div>
      <input {...text('username')} />
      <input {...password('password')} />
      <button disabled={formState.isPristine()} onClick={handleSubmit}>
        Login
      </button>
    </div>
  );
}

Checking if a field is pristine is done with simple equality ===, with some exceptions. This can be overridden per field by providing a custom compare function.

Note that a compare function is required for raw inputs, otherwise, if not specified, the pristine value of a raw input will always be set to false after a change.

<input
  {...raw({
    name: 'userObj',
    compare(initialValue, value) {
      // returns a boolean indicating if the changed value is equal to the initial value
      return isEqualDeep(initialValue, value);
    },
  })}
/>

Without Using a <form /> Element

useFormState is not limited to actual forms. It can be used anywhere inputs are used.

function LoginForm({ onSubmit }) {
  const [formState, { email, password }] = useFormState();
  return (
    <div>
      <input {...email('email')} required />
      <input {...password('password')} required minLength="8" />
      <button onClick={() => onSubmit(formState)}>Login</button>
    </div>
  );
}

Labels

As a convenience, useFormState provides an optional API that helps with pairing a label to a specific input.

When formOptions.withIds is enabled, a label can be paired to an input by using input.label(). This will populate the label's htmlFor attribute for an input with the same parameters.

const [formState, { label, text, radio }] = useFormState(initialState, {
  withIds: true, // enable automatic creation of id and htmlFor props
});

return (
  <form>
    <label {...label('name')}>Full Name</label>
    <input {...text('name')} />

    <label {...label('plan', 'free')}>Free Plan</label>
    <input {...radio('plan', 'free')} />

    <label {...label('plan', 'premium')}>Premium Plan</label>
    <input {...radio('plan', 'premium')} />
  </form>
);

Note that this will override any existing id prop if specified before calling the input functions. If you want the id to take precedence, it must be passed after calling the input types like this:

<input {...text('username')} id="signup-username" />

Custom Controls

useFormState provides a raw type for working with controls that do not use React's SyntheticEvent system. For example, controls like react-select or react-datepicker have onChange and value props that expect a custom value instead of an event.

To use this, your custom component should support an onChange() event which takes the value as a parameter, and a value prop which is expected to contain the value. Note that if no initial value is given, the component will receive a value prop of an empty string, which might not be what you want. Therefore, you must provide an initial value for raw() inputs when working with custom controls.

import DatePicker from 'react-datepicker';

function Widget() {
  const [formState, { raw }] = useFormState({ date: new Date() });
  return (
    <>
      <DatePicker {...raw('date')} />
    </>
  );
}

You can also provide an onChange option with a return value in order to map the value passed from the custom control's onChange to a different value in the form state.

function Widget() {
  const [formState, { raw }] = useFormState({ date: new Date() });
  return (
    <>
      <DatePicker
        {...raw({
          name: 'date',
          onChange: date => date.toString();
        })}
        value={new Date(formState.date)}
      />
    </>
  );
}

Note that onChange() for a raw value must return a value.

Many raw components do not support onBlur() correctly. For these components, you can use touchOnChange to mark a field as touched when it changes instead of on blur:

function Widget() {
  const [formState, { raw }] = useFormState({ date: new Date() });
  return (
    <>
      <CustomComponent
        {...raw({
          name: 'date',
          touchOnChange: true,
        })}
      />
    </>
  );
}

Updating Fields Manually

There are cases where you may want to update the value of an input manually without user interaction. To do so, the formState.setField method can be used.

function Form() {
  const [formState, { text }] = useFormState();

  function setNameField() {
    // manually setting the value of the "name" input
    formState.setField('name', 'Mary Poppins');
  }

  return (
    <>
      <input {...text('name')} readOnly />
      <button onClick={setNameField}>Set Name</button>
    </>
  );
}

Please note that when formState.setField is called, any existing errors that might have been set due to previous interactions from the user will be cleared, and both of the validity and the touched states of the input will be set to true.

It's also possible to clear a single input's value or to reset it to its initial value, if provided, using formState.clearField and formState.resetField respectively.

As a convenience you can also set the error value for a single input using formState.setFieldError.

Resetting The Form State

The form state can be cleared or reset back to its initial state if provided at any time using formState.clear and formState.reset respectively.

function Form() {
  const [formState, { text, email }] = useFormState({
    email: '[email protected]',
  });
  return (
    <>
      <input {...text('first_name')} />
      <input {...text('last_name')} />
      <input {...email('email')} />
      <button onClick={formState.clear}>Clear All Fields</button>
      <button onClick={formState.reset}>Reset to Initial State</button>
    </>
  );
}

Working with TypeScript

When working with TypeScript, the compiler needs to know what values and inputs useFormState is expected to be working with.

For this reason, useFormState accepts an optional type argument that defines the state of the form and its fields which you could use to enforce type safety.

interface LoginFormFields {
  username: string;
  password: string;
  remember_me: boolean;
}

const [formState, { text }] = useFormState<LoginFormFields>();
                                          ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
// OK
<input {...text('username')} />
formState.values.username

// Error
formState.values.doesNotExist
<input {...text('doesNotExist')} />

By default, useFormState will use the type any for the form state and its inputs if no type argument is provided. Therefore, it is recommended that you provide one.

By default, the errors property will contain strings. If you return complex error objects from custom validation, you can provide an error type:

interface I18nError {
  en: string;
  fr: string;
}

interface LoginFormErrors {
  username?: string | I18nError;
  password?: string;
}

const [formState, { text }] = useFormState<LoginFormFields, LoginFormErrors>();

formState.errors.username; // Will be undefined, a string, or an I18nError.

API

import { useFormState } from 'react-use-form-state';

function FormComponent()
  const [formState, inputs] = useFormState(initialState, formOptions);
  return (
    // ...
  )
}

initialState

useFormState takes an optional initial state object with keys as the name property of the form inputs, and values as the initial values of those inputs (similar to defaultValue/defaultChecked).

formOptions

useFormState also accepts an optional form options object as a second argument with following properties:

formOptions.onBlur

A function that gets called upon any blur of the form's inputs. This functions provides access to the input's blur SyntheticEvent

const [formState, inputs] = useFormState(null, {
  onBlur(e) {
    // accessing the inputs target that triggered the blur event
    const { name, value, ...target } = e.target;
  },
});

formOptions.onChange

A function that gets triggered upon any change of the form's inputs, and before updating formState.

This function gives you access to the input's change SyntheticEvent, the current formState, the next state after the change is applied.

const [formState, inputs] = useFormState(null, {
  onChange(e, stateValues, nextStateValues) {
    // accessing the actual inputs target that triggered the change event
    const { name, value, ...target } = e.target;
    // the state values prior to applying the change
    formState.values === stateValues; // true
    // the state values after applying the change
    nextStateValues;
    // the state value of the input. See Input Types below for more information.
    nextStateValues[name];
  },
});

formOptions.onTouched

A function that gets called after an input inside the form has lost focus, and is marked as touched. It will be called once throughout the component life cycle. This functions provides access to the input's blur SyntheticEvent.

const [formState, inputs] = useFormState(null, {
  onTouched(e) {
    // accessing the inputs target that triggered the blur event
    const { name, value, ...target } = e.target;
  },
});

formOptions.onClear

A function that gets called after calling formState.clear indicating that all fields in the form state are cleared successfully.

const [formState, inputs] = useFormState(null, {
  onClear() {
    // form state was cleared successfully
  },
});

formState.clear(); // clearing the form state

formOptions.onReset

A function that gets called after calling formState.reset indicating that all fields in the form state are set to their initial values.

const [formState, inputs] = useFormState(null, {
  onReset() {
    // form state was reset successfully
  },
});
formState.reset(); // resetting the form state

formOptions.validateOnBlur

By default, input validation is performed on both of the change and the blur events. Setting validateOnBlur to true will limit input validation to be only performed on blur (when the input loses focus). When set to false, input validation will only be performed on change.

formOptions.withIds

Indicates whether useFormState should generate and pass an id attribute to its fields. This is helpful when working with labels.

It can be one of the following:

A boolean indicating whether input types should pass an id attribute to the inputs (set to false by default).

const [formState, inputs] = useFormState(null, {
  withIds: true,
});

Or a custom id formatter: a function that gets called with the input's name and own value, and expected to return a unique string (using these parameters) that will be as the input id.

const [formState, inputs] = useFormState(null, {
  withIds: (name, ownValue) =>
    ownValue ? `MyForm-${name}-${ownValue}` : `MyForm-${name}`,
});

Note that when withIds is set to false, applying input.label() will be a no-op.

[formState, inputs]

The return value of useFormState. An array of two items, the first is the form state, and the second an input types object.

Form State

The first item returned by useFormState.

const [formState, inputs] = useFormState();

An object containing the form state that updates during subsequent re-renders. It also include methods to update the form state manually.

formState = {
  // an object holding the values of all input being rendered
  values: {
    [name: string]: string | string[] | boolean,
  },

  // an object indicating whether the value of each input is valid
  validity: {
    [name: string]?: boolean,
  },

  // an object holding all errors resulting from input validations
  errors: {
    [name: string]?: any,
  },

  // an object indicating whether the input was touched (focused) by the user
  touched: {
    [name: string]?: boolean,
  },

  // an object indicating whether the value of each input is pristine
  pristine: {
    [name: string]: boolean,
  },

  // whether the form is pristine or not
  isPristine(): boolean,

  // clears all fields in the form
  clear(): void,

  // clears the state of an input
  clearField(name: string): void,

  // resets all fields the form back to their initial state if provided
  reset(): void,

  // resets the state of an input back to its initial state if provided
  resetField(name: string): void,

  // updates the value of an input
  setField(name: string, value: string): void,

  // sets the error of an input
  setFieldError(name: string, error: string): void,
}

Input Types

The second item returned by useFormState.

const [formState, input] = useFormState();

An object with keys as input types. Each type is a function that returns the appropriate props that can be spread on the corresponding input.

The following types are currently supported:

Input Options

Alternatively, input type functions can be called with an object as the first argument. This object is used to extend the functionality of the input. This includes attaching event handlers and performing input-level custom validation.

<input
  {...input.text({
    name: 'username',
    validate: value => validateUsername(value),
    validateOnBlur: true,
  })}
/>

The following options can be passed:

License

MIT