Fully customisable react form utility.

🌈 Features

• Typescript compatible
• Customizable extractor, validator, getter and setters. (More in the docs)
• 0 Dependencies
• Tiny ~0.7kB
• React Hooks

Installation

npm i formhero

👁 Demos

• Live Web
• Live Codesandbox
• Live React-Native

Links

• Examples
• Docs
  • Contructor
    • Initial State
    • Validators
    • Options
  • Returns
    • field
    • form
    • errors
    • isValid
    • setField
    • setForm
    • setErrors

🤔 Motivation

So why write yet another form utility you might ask? First off, I don't like the Formik approach. In my humble opition formik is very verbose and requires lots of boilerplate. Also does not work with hooks. react-hook-form is a very cool library and it is the main inspiration for formhero. It does almost everything right... typescript, no deps, small, concise.

The problem that I found while using it was that 3rd party ui libs like Ant Design or Fabric UI do not always have the standart onChange or value props in their components. That is where react-hook-form starts falling apart. This is what formhero tries to address in the most minimalistic way possible, with as little code as needed. All in pure typescript and no deps.

🚀 Quickstart

import ReactDOM from 'react-dom'
import { useForm } from 'formhero'

const Form = () => {
  const { field, form } = useForm({
    username: '',
    password: '',
  })

  const _submit = (e: React.FormEvent) => {
    e.preventDefault()
    console.log(form)
  }

  return (
    <div>
      <form onSubmit={_submit}>
        <input {...field('username')} />
        <input {...field('password')} />

        <button type="submit">Go 🚀</button>
      </form>
    </div>
  )
}

🔥 Examples (More Here)

Validation

const Form = () => {
  const { field, form, errors } = useForm(
    {
      username: '',
      email: '',
      password: '',
    },
    {
      username: value => value.length > 3,
      email: {
        validator: /@/,
        message: 'Must contain an @',
      },
      password: [
        {
          validator: /[A-Z]/,
          message: 'Must contain an uppercase letter',
        },
        {
          validator: /[\d]/,
          message: 'Must contain a digit',
        },
      ],
    }
  )

  return (
    <form>
      <h1>Errors & Validation</h1>

      <input {...field('username')} placeholder="Username" />
      {errors.username && 'Must be longer than 3'}

      <input {...field('email')} placeholder="EMail" />
      {errors.email}

      <input {...field('password')} placeholder="Password" type="password" />
      {errors.password}
    </form>
  )
}

Easy Customization

Often it happens that you use a specific input or framework, so the default getter, setter and extractor for the event won't cut it. No worries: formhero got you covered!

const Form = () => {
  const { field, form, errors } = useForm({
    awesome: true,
  })

  return (
    <form
      onSubmit={e => {
        e.preventDefault()
        console.log(form)
      }}
    >
      <h1>Custom</h1>

      <label>
        <input
          type="checkbox"
          {...field('awesome', {
            setter: 'checked',
            getter: 'onChange',
            extractor: e => e.target.checked,
          })}
        />
        Is it awesome?
      </label>

      <input type="submit" />
    </form>
  )
}

Dynamic Fields

Sometimes you don't know all the fields upfront. You can simply define a generic type and assign it to the initial object. Of course type assistance is limited in this case as formhero cannot be sure what keys are valid.

import React from "react";
import ReactDOM from "react-dom";
import { useForm } from "formhero";

type MyForm = { [field: string]: string | number };

const init: MyForm = {
  username: "unicorn",
  password: ""
};

const Form: React.FC = () => {
  const { field, form, errors } = useForm(init);

  return (
    <form>
      <input {...field("username")} placeholder="Username" />
      <input {...field("someother")} placeholder="Something else" />
      <input {...field("password")} placeholder="Password" type="password" />
    </form>
  );
};

📖 Documentation

useForm

const { field, errors, update, form, isValid } = useForm(initial, validators, options)

Initial

This is the base state of the form. Also the typescript types are inhered by this.

Example

const initial = {
  username: 'defaultValue',
  password: '',
  rememberMe: true,
}

Validators

A validator is an object that taked in either a RegExp or a Function (can be async) or an array of those. Optionally you can pass a message string that will be displayed instead of the default one.

A validator functions takes the current value as input and should return a boolean or a string. If returned true the input counts as valid, if false it's not. If you pass a string formhero will treat it as not valid and display the string returned as error message.

Example: Regular Expression

const validators = {
  // Only contains letters.
  // This could also be a (also async) function that returns a boolean.
  username: /^[A-z]*$/,
}

Example: Function

const validators = {
  username: (value: string) => value.lenght > 3,
}

Example: With Object

const validators = {
  username: {
    validator: /^[A-z]*$/,
    message: 'My custom error message',
  },
}

Example: Multiple Validators

const validators = {
  username: [
    {
      validator: /^[A-z]*$/,
      message: 'My custom error message',
    },
    /[\d]/,
    async value => value.length > 0,
    {
      validator: value => true,
      message: 'Some other error',
    },
  ],
}

Example: Dynamic Error Message

const validators = {
  username: async (s: string) => {
    const taken = await API.isUsernameTaken(s)
    return taken ? 'Username is taken': true
  }
}

Options

Sometimes it's practical to have some different default values when using for example react-native or some other framework where the default value, onChange and (e)=> e.target.value do not apply.

Example: React Native (Method 1 - Global options)

Check the Expo Snack for a live preview

import * as React from 'react'
import { Text, SafeAreaView, TextInput } from 'react-native'
import { useForm } from 'formhero'

const initial = {
  username: 'i am all lowercase',
}
const validators = {}
const options = {
  setter: 'value', // This is not stricly necessarry as 'value' would already be the default.
  getter: 'onChangeText',
  extractor: text => text.toLowerCase(),
}

export default () => {
  const { form, field } = useForm(initial, validators, options)

  return (
    <SafeAreaView>
      <TextInput style={{ height: 40, borderColor: 'gray', borderWidth: 2 }} {...field('username')} />
      <Text>{form.username}</Text>
    </SafeAreaView>
  )
}

Example: React Native (Method 2 - Local overwrite)

// ...

export default () => {
  const { form, field } = useForm({
    username: 'i am all lowercase',
  })

  return (
    <SafeAreaView>
      <TextInput
        style={{ height: 40, borderColor: 'gray', borderWidth: 2 }}
        {...field('username', {
          setter: 'value', // This is not stricly necessarry as 'value' would already be the default.
          getter: 'onChangeText',
          extractor: text => text.toLowerCase(),
        })}
      />
      <Text>{form.username}</Text>
    </SafeAreaView>
  )
}

field

The field object is used to bind the form state to the input.

Example: Simple

const { field } = useForm()

<input {...field('username')} />

Example: With custom options

All are optional.

const { field } = useForm()

<input {...field('username', {
  getter: 'onChage',
  setter: 'value',
  extractor: (e) => e.target.value
})} />

Form

This is the form state that you can use when submitting the data

Example

const { form } = useForm(...);

// ...

<form onSubmit={()=> console.log(form)}>
  // ...
</form>

Errors

This object contains the error messages if a field is not valid. The error message can be specified by you, otherwise it will return Error in ${field}

Example

const { errors } = useForm(...)

//...

{errors.username}
{errors.password}

isValid

isValid is a little simple helper that checks whether the error object is clear or if there are errors left.

setField

The setField function allows you to manually change and assign the state of a field. The type of the field must be the same as the initial type given in the constructor.

Example

const { form, setField } = useForm(...)

const resetUsername = () => {
  setField('username', 'new value')
}

setForm

The setForm function allows you to manually change and assign the state of the form. This can be usefull when you want to reset a field or the whole form. The input must have the same type as the initial state.

Example

const initial = {username: '', password: ''}

const { form, setForm } = useForm(initial, ...)

const resetForm = () => {
  setForm(initial)
}

setErrors

The setErrors function allows you to manually change and assign the state of the errors. This can be usefull when you want to set an error manually (e.g. sent from the server).

Example

const { form, setErrors } = useForm(...)

const setError = () => {
  setErrors({username: 'Already taken'})
}

Thanks & Attributions

• Thanks for brendanmckenzie for suggesting to change auto to field.