@andydowell/use-form-state/README.md

A React hook for managing form state and validation

# FormState React Hook

The `useFormState` hook is a utility for managing form state in React applications. It provides functionality for tracking and validating form fields, as well as extracting form data in different formats. With `useFormState`, you can easily handle form interactions and ensure data integrity.

## Installation

To install the `use-form-state` package, run the following command:

```shell
npm install @andydowell/use-form-state
```

## Usage

### Initializing the Form State

```javascript
import { useFormState } from "@andydowell/use-form-state";

const formState = useFormState(formFieldParams, options);
```

Before using the hook, you need to define the `formFieldParams`. These props represent the structure of your form and include information such as default values, validation rules, and error messages.

Each field in the `formFieldParams` is defined by a key-value pair, where the key is the name of the field and the value is an object with the following properties:

| Property     | Description                                                                                                                                                                                                                             | Type                                                               | Example                                                                                                                |
| ------------ | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------ | ---------------------------------------------------------------------------------------------------------------------- |
| defaultValue | The default value for the form field.                                                                                                                                                                                                   |                                                                    | ""                                                                                                                     |
| required     | (Optional) Specifies whether the form field is required.                                                                                                                                                                                | { message: string }                                                | { message: "Please enter your email address" }                                                                         |
| validation   | (Optional) An object that defines custom validation rules for the form field. Each rule is represented by a key-value pair, where the key is the name of the rule and the value is an object with `validator` and `message` properties. | `{[key]: {validator: (value, state) => boolean, message: string}}` | `{ longerThanOneChar: { validator: value => value.length > 1, message: 'Password must be longer than 1 character' } }` |
| label        | (Optional) Default as empty string (`""`).                                                                                                                                                                                              | string                                                             | 'Email'                                                                                                                |
| helperText   | (Optional) Text that provides additional information or guidance for the form field.                                                                                                                                                    | string                                                             | 'Please enter a valid email'                                                                                           |

The second parameter `options` is an object with the following properties:

| Property                  | Type   | Description                                                                                   |
| ------------------------- | ------ | --------------------------------------------------------------------------------------------- |
| errorUpdateDelayInSeconds | number | (Optional) Specifies the delay in seconds before the error type is updated. Default is `0.5`. |

You can see an example of `formFieldParams` and `options` in the [Example](#example) section.

## API

The `useFormState` hook returns an object with the following properties and methods:

```javascript
const { state, set, update, checkIfAllValid, extractStateValue, reset } = useFormState(formFieldParams, options);
```

The `state` object contains the current values and validation status of each form field. <br/>
The `set` function allows you to update single form field value. <br/>
The `update` function allows you to update multiple form field values. <br/>
The `checkIfAllValid` function checks if all fields are valid. <br/>
The `extractStateValue` function extracts the form data in the specified format. <br/>
The `reset` function resets the form to its initial state. <br/>

### Form State

Each form field in the `state` object is represented by an object with the following properties:

| Property       | Description                                                                                                                                                                                                           | Example Usage                                                                    | Example Output                                                     |
| -------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------- | ------------------------------------------------------------------ |
| `value`        | The current value of the form field.                                                                                                                                                                                  | `state.email.value`                                                              |
| `isValid`      | Indicates whether the value of the form field is valid. Required fields are considered valid if they are filled. If validation param is provided, the value will be validated against the validator functions inside. | `state.email.isValid`                                                            |
| `isInteracted` | Indicates whether the form field has been interacted with (user has changed the value).                                                                                                                               | `state.email.isInteracted`                                                       |
| `isRequired`   | Indicates whether the form field is required.                                                                                                                                                                         | `state.email.isRequired`                                                         |
| `label`        | The label of the form field.                                                                                                                                                                                          | `state.email.label`                                                              | 'Email'                                                            |
| `helperText`   | A helper text that provides additional information or instructions for the form field.                                                                                                                                | `state.email.helperText`                                                         |
| `error`        | An object that represents an error associated with the form field. It has two properties: `type` (the type of error) and `message` (the error message). If there is no error, this property will be `undefined`.      | `state.email.error`<br>`state.email.error?.type`<br>`state.email.error?.message` | `{ type: "required", message: "Please enter your email address" }` |

`error` is not updated immediately when the value of a form field changes. Instead, it is updated after a delay (default is 0.5 seconds) to prevent the error message from flashing when the user is typing. If the field is not interacted with, the error will not be updated. Running `checkIfAllValid({ updateErrorType: true })` will update all errors immediately.

### Updating Single Form Field Value

To update a form field value, use the `set` function:

```javascript
set(key, value, setInteracted);
```

| Parameter       | Type                      | Description                                                                               | Example                 |
| --------------- | ------------------------- | ----------------------------------------------------------------------------------------- | ----------------------- |
| `key`           | string                    | The key of the field in the form state.                                                   | `'email'`               |
| `value`         | (type of the field value) | The new value to be set for the field.                                                    | `'example@example.com'` |
| `setInteracted` | boolean                   | (Optional) Indicates whether the field should be marked as interacted. Default is `true`. | `false`                 |

You can see an example of `set` in the [Example](#example) section.

### Updating Multiple Form Field Values

To update multiple form field values at once, use the `update` function:

```javascript
update(data, setInteracted);
```

| Parameter     | Type    | Description                                                                                   | Example                                                 |
| ------------- | ------- | --------------------------------------------------------------------------------------------- | ------------------------------------------------------- |
| data          | object  | An object with key-value pairs where the key is the field key and the value is the new value. | `{ email: "", password: "" }` |
| setInteracted | boolean | (Optional) Indicates whether the fields should be marked as interacted. Default is `true`.    | `false`                                                 |

You can see an example of `update` in the [Example](#example) section.

### Checking Form Field Validity

You can check the validity of individual form fields by accessing the `isValid` property in the `state` object:

```javascript
const isEmailValid = state.email.isValid;
```

### Checking Overall Form Validity

To check if the entire form is valid, use the `checkIfAllValid` function:

```javascript
const isFormValid = checkIfAllValid(options);
```

The `options` parameter is an object with the following properties:

| Parameter         | Type    | Description                                                                                      |
| ----------------- | ------- | ------------------------------------------------------------------------------------------------ |
| `updateErrorType` | boolean | (Optional) Specifies whether the error types of all fields should be updated. Default is `true`. |

The validation will check all form fields based on their defined rules and update their validation status and error messages accordingly. <br/>
You can see an example of `checkIfAllValid` in the [Example](#example) section.

### Extracting Form Data

You can extract the form data in different formats using the `extractStateValue` function. Currently, two formats are supported: `'object'` and `'formdata'`.

Example:<br/>
To extract the form data as an object:

```javascript
const dataObject = extractStateValue({ format: "object" });
```

To extract the form data as FormData:

```javascript
const formData = extractStateValue({ format: "formdata" });
```

You can see an example of `extractStateValue` in the [Example](#example) section.

### Resetting the Form

To reset the form to its initial state, use the `reset` function:

```javascript
reset();
```

This will clear all form field values and reset their validation status. <br/>
You can see an example of `reset` in the [Example](#example) section.

## Example

```javascript
const newUser = useFormState({
  email: {
    defaultValue: "@",
    helperText: "Your Email Address",
    required: { message: "Please enter your email address" },
    validation: {
      longerThanOneChar: {
        validator: value => value.length > 1,
        message: "Email address must be longer than 1 character",
      },
      ["has-add-sign"]: {
        validator: value => value.includes("@"),
        message: "Email address must contain '@'",
      },
    },
  },
  password: {
    defaultValue: "",
    helperText: "Your Password",
    required: { message: "Please enter your password" },
    validation: {
      longerThanOneChar: {
        validator: value => value.length > 1,
        message: "Password must be longer than 1 character",
      },
    },
  },
  confirmPassword: {
    defaultValue: "",
    helperText: "Confirm Your Password",
    required: { message: "Please enter your password again" },
    validation: {
      longerThanOneChar: {
        validator: value => value.length > 1,
        message: "Password must be longer than 1 character",
      },
      matchPassword: {
        validator: (value, state) => value === state.password.value,
        message: "Passwords do not match",
      },
    },
  },
});

// ---------------------------------

const onSubmit = async e => {
  e.preventDefault();
  if (!newUser.checkIfAllValid()) return;

  const formdata = newUser.extractStateValue({ format: "formdata" });
  // ... Submit formdata to server
};

// ---------------------------------

const { email, password, confirmPassword } = newUser.state;

<form onSubmit={onSubmit}>
  <div>
    <Input value={email.value} onChange={e => newUser.update({ email: e.target.value })} />
    <p>{email.error?.message || email.helperText}</p>
  </div>
  <div>
    <Input type="password" value={password.value} onChange={e => newUser.set("password", e.target.value)} />
    <p>{password.error?.message || password.helperText}</p>
  </div>
  <div>
    <Input
      type="password"
      value={confirmPassword.value}
      onChange={e => newUser.set("confirmPassword", e.target.value)}
    />
    <p>{confirmPassword.error?.message || confirmPassword.helperText}</p>
  </div>
  <button type="submit">Submit</button>
  <button type="reset" onClick={newUser.reset}>
    Reset
  </button>
</form>;
```

## License

This package is open source and available under the [MIT License](https://opensource.org/licenses/MIT).