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WARNING: This project has been renamed to re-use-form. Install using re-use-form instead.

ok-react-use-form

React Form Hook

Simple and robust form hook for React with validation support and simple internationalization.

Installation

npm install --save ok-react-use-form

Usage

Input Prerequisites

ok-react-use-form provides a useForm and useControlledForm hooks that are intended to be used alongside with custom Input components. An Input is any component that consumes three properties: value, error and onChange (note that there is also name property supplied for input by form's helpers). It also has to provide it's value as first argument to onChange function supplied in props.

useForm Hook

ok-react-use-form provides useForm hook for uncontrolled forms. It accepts object with initial form attributes and optional config. Config can be used to define client-side validations (see "Form Validations" section bellow) and to ease internationalization.

import { useForm } from 'ok-react-use-form';
import { TextField, Select } from 'my-components/inputs';
 
function MyForm({onSave}) {
  const {input, get} = useForm({}); // initialize form attributes with empty object.
 
  const save = () => onSave(get()); // get() returns all current form state
 
  return (
    <>
      <TextField { ...input("email") } label="Email" />
      <TextField { ...input("fullName") } label="Full Name" />
 
      <Select { ...input("address.countryId") } options={ countryOptions } label="Country" />
      <TextField { ...input("address.city") } label="City" />
      <TextField { ...input("address.line") } label="Address" />
 
      <button onClick={ save }>Submit</button>
    </>
  );
}

Note on $ alias for input helper.

useForm hook returns an object that has both input and $ keys with the same value. While input is more explicit name, it might become cumbersome to use it over and over again. For this reason, useForm hook also provides a $ helper that does the same. Basically, it's the same approach as used in react-form-base package. All examples bellow will use $ helper method as more common one.

Hook Config

useForm hook accepts a config as a second argument. This config object is mainly used for declaring form validations and is memoized by default. Also, config itself may be replaced by validation rules (see "Form Validations" section bellow), removing need of extra nesting.

Bellow are examples of useForm hook call with valid configs:

// Using input validation setup directly in place of config:
const {$} = useForm({}, {
  username: "presence"
});

To be able to have dynamic config, you should disable default memoization by using useMemo: false config option. But doing just this is highly discouraged, since on each render hook will receive new object literal re-setting config with no real changes every time. So whenever you disable default memoization, make sure to provide custom one with proper dependencies:

const [validationEnabled, setValidationEnabled] = useState(false);
const {$} = useForm({}, useMemo(() => ({
  useMemo: false,
  validations: validationEnabled && {
    username: "presence"
  }
}), [validationEnabled]));

Finally, in cases when validation setup needs to share common options for all validation rules (like for internationalizing error messages, see corresponding section bellow), you can specify defaultOptions within validation setup:

const {t} = useTranslation("common");
const {$} = useForm({}, {
  validations: {
    defaultOptions: {t},
    rules: {
      username: "presence"
    }
  }
});

Custom onChange Input Handler

The most common use-case when you need custom logic is to have custom onChange handler for handling any input's change. For this, $/input function takes this function as second attribute. This function will be called with input name as first argument and input value as second one:

function Form() {
  const {$, set} = useForm({});
 
  // uppercases user's input
  const changeInput = useCallback((name, value) => {
    set(name, value.toUpperCase());
  }, []);
 
  return (
    <>
      <TextField { ...$('username', changeInput) } label="Username" />
      <TextField { ...$('address.postalCode', changeInput) } label="Postal Code" />
    </>
  );
}

Purity Support

All of the helper functions returned by useForm hook, with the exception of get and getError functions that depends on form attributes and errors whenever they change, are persistent and do not change on per render basis. The same goes for values returned by $/input helper - as long as on-change handler passed to $ function is persistent (or if it was omitted), it's onChange property will be persistent as well, i.e. pure input components that consume it won't be re-rendered if other properties do not change too.

If, for some reason, you want to disable input onChange handlers persistence, you can use pureHandlers: false config option.

Note on Validation-less Forms

Before we go to validation section bellow, it should be mentioned that even forms without defined client-side validation can use getError, setErrors and setError helpers returned by form hook. With no client-side validation, you might still want to interact with the server when user works with form and should something go wrong, you might want to set server-side errors for form's inputs and use them in form's rendering logic, which is exactly what mentioned helpers are about.

Form Validations

ok-react-use-form provides a very easy way to declare form validations, which will automatically validate inputs on change when required. Each validation rule is defined via defValidation function call. Validation handler function used in this call should accept two arguments - input's value and validation options. Even considering that not all validation rules need additional options for their business logic, the most common use case scenario is to allow user to specify custom error message when validation is failed.

import { defValidation } from "ok-react-use-form";
 
// Bellow are very primitive validations defined for demonstration purposes.
// All validation rules should be defined only once on your app initialization.
defValidation("presence", (value, {message}) => {
  if (!value) {
    return message || "Cannot be blank";
  }
});
 
defValidation("email", (value, {message}) => {
  if (!value) return;
 
  if (!/.+@.+/.test(value)) {
    return message || "Should be a valid email address";
  }
});
 
defValidation("format", (value, {pattern, message}) => {
  if (!value) return;
 
  if (!pattern.test(value)) {
    return message || "Invalid format";
  }
});

With generic validations defined, they can be used in form hook (alongside with custom function validations, if needed)

// UserForm.js
// ...other imports...
import { useForm } from 'ok-react-use-form';
 
function UserForm() {
  const {$, validate} = useForm({}, {
    "email": ["presence", "email"],
    "fullName": "presence",
    "address.city": ["presence", function(value) {
      if (!value) return;
 
      if (!/^[A-Z]/.test(value)) {
        return "Should start with capital letter";
      }
    }],
    "address.line": {
      presence: true,
      format: {
        pattern: /^[\w\s\d\.,]+$/,
        message: "Please enter a valid address"
      }
    }
  });
 
  const save = useCallback(() => {
    validate()
      .then((attrs) => {
        // Do something on successful validation.
        // `attrs` is identical to `get()` helper call
      })
      .catch((errors) {
        // Do something if validation failed. At this moment
        // errors are already rendered.
        // It is safe to omit this `.catch` closure - no
        // exception will be thrown.
      });
  });
 
  return (
    <>
      <TextField { ...$("email") } label="Email" />
      <TextField { ...$("fullName") } label="Full Name" />
 
      <Select { ...$("address.countryId") } options={ countryOptions } label="Country" />
      <TextField { ...$("address.city") } label="City" />
      <TextField { ...$("address.line") } label="Address" />
 
      <button onClick={ save }>Submit</button>
    </>
  );
}

It's up to you how to define validation rules. But as for suggested solution, you might want to take a look at validate.js project and adopt it's functionality for validation definitions.

Wildcard Validation

If your form deals with collections of items, it is possible to declare validation for them using wildcards:

function OrderForm() {
  const {$} = useForm({items: []}, {
    "email": ["presence", "email"],
    "items.*.name": "presence",
    "items.*.count": {
      presence: true,
      numericality: {greaterThan: 10}
    }
  });
 
  // ...
}

withValidation Helper

It's pretty common to perform some action as soon as form has no errors and validation passes. For such case there is withValidation helper that accepts a callback and wraps it in validation routines. This callback will be called only if form had no errors:

const {$, withValidation} = useForm({}, {
  name: "presence"
});
 
const save = (attrs) => {
  // send `attrs` to server
};
 
return (
  <>
    <Input { ...$("name") } />
    <button onClick={ withValidation(save) }>Submit</button>
  </>
);

Form Partials (usePartial Helper Hook)

One of the features of ok-react-use-form package is that it's useForm hook also provides a usePartial helper, which is a hook itself, and can be used to define "nested" forms with their own validation and other business logic. This can help you improve code organization and extract independent parts into dedicated components for better maintainability.

function OrderForm() {
  const {$, get, validate, usePartial} = useForm({username: "", items: [{}]}, {
    username: "presence"
  });
 
  return (
    <div>
      <Input { ...$("username") } className="username" />
      { get("items").map((item, i) => (
          <ItemForm key={ i } usePartial={ usePartial } index={ i } />
        ))
      }
      <button onClick={ validate }>Validate</button>
    </div>
  );
}
 
function ItemForm({usePartial, index}) {
  const {$} = usePartial(`items.${index}`, {
    name: "presence",
    count: "presence"
  });
 
  return (
    <div>
      <Input { ...$("name") } />
      <Input { ...$("count") } />
    </div>
  );
}

There are couple of limitations in usePartial hook, however:

• As second parameter it can accept only validation rules object (i.e. it is not configurable in any other way)
• Validation is memoized for the lifespan of the component, i.e. it cannot be dynamic.

Internationalized Validation Error Messages

Depending on adopted i18n solution in your application, there are different ways of internationalizing validation error messages. The most common ones would include global t function and hook-based t function.

Global t Function

Projects like ttag give you a global t function with gettext-like usage. Probably, this approach provides the most simple and easy-to-use way to internationalize error messages:

import { defValidation } from "ok-react-use-form";
import { t } from "ttag";
 
defValidation("presence", (value, {message}) => {
  if (!value) {
    return message || t`Can't be blank`;
  }
});

Hook-based t Function

Frameworks like react-i18next provide translation hooks to be used within components themselves. In case of react-i18next we have a useTranslation hook, which provides access to t function. Since this function is locally scoped to component, it should be passed to validation options explicitly. Luckily, useForm hook allows to provide default validation options to have this t function specified only once without need to explicitly mention it over and over again:

import { defValidation } from "ok-react-use-form";
 
defValidation("presence", (value, {t, message}) => {
  if (!value) {
    return message || t("errors.cannot_be_blank");
  }
});

And then in form:

import { useForm } from "ok-react-use-form";
import { useTranslation } from "react-i18next";
 
export function Form() {
  const {t} = useTranslation("common");
  const {$} = useForm({}, {
    validations: {
      defaultOptions: {t},
      rules: {
        username: "presence",
        email: ["presence", "email"]
      }
    }
  });
 
  // rest of component
}

Hook helper object

useForm hook returns object with following properties:

• $(name), input(name) - returns a set of properties for input with a given name. name is a dot-separated string, i.e. 'foo.bar' (for bar property nested in object under foo), or 'foos.1' (value at index 1 of foos array), or 'foos.2.bar' (bar property of object at index 2 of foos array)
• get(name) - returns a value for a given name. For example, if you have an attributes like {foos: [{bar: 'baz'}, {bar: 'bak'}]}, you might have:
  • get('foos') // => [{bar: 'baz'}, {bar: 'bak'}]
  • get('foos.1') // => {bar: 'bak'}
  • get('foos.1.bar') // => 'bak'
  • get() // returns whole form's attributes object
• set(name, value) - sets a value for an input with a specified name.
• set(object) - sets multiple values at once. Each key in the object corresponds to input name, and values are input values.
• errors - object representing all validation errors.
• getError(name) - returns validation error for an input with a given name.
• setErrors(errors) - sets errors (object) as form's errors.
• setError(name, error) - sets an error for a single input with a given name.
• validate({onValid, onError}) - performs form validations. Accepts an object with onValid and onError callbacks that will be called in case of successful/failed validation correspondingly.
• withValidation(callback) - performs form validation and executes a callback if there were no errors.
• reset(initial) - clears form errors and sets form attributes provided value. If no value provided, uses object that was passed to initial useForm hook call.

Better Naming

Naming variables is hard. Naming npm packages is even harder. Especially considering that names can be taken. Since ok-react-use-form is pretty cumbersome to write over and over again, there are few options that can improve usage experience:

• Webpack users can use resolve.alias configuration option to set up an alias like use-form to use within application.
• The most generic solution would be to re-export package functionality from some part of your application, alongside with your inputs. For instance, you might have /components/form/index.js file with following content:

  export * from "ok-react-use-form";
  export * from "./inputs";

  And then in your logic components you might have:

  import { useForm, Input } from "components/form";

License

MIT