Formular

Easy way to work with forms in React. Using React Hooks 😏

❤️ Just 3kb gzip

❤️ React hooks

❤️ TypeScript

❤️ Changes made within form rerender only changed fields

Installation

npm install formular

Philosophy

There are many form libraries that works out of the box - "import Form, Field and that's it". But in most projects common fields are customized by design and usage of Form, Field components become impossible. Formular doesn't provide inboxing components for fast start, but it provides easy way to attach form functionality to custimized fields!

For example you have your own styled Input component with specific logic inside

import { useField, useFieldState } from 'formular'

const FormularInput = () => {
  const field = useField()
  const state = useFieldState(field)

  return <CustomInput value={state.value} onChange={field.set} />
}

useField is a wrapper for new Field:

const useField = (opts, deps) => useMemo(() => new Field(opts), deps || [])

So when field's state updates FormularSelect doesn't render. Here useFieldState comes, it triggers react state update which call component's render.

This is Field, and whats about Form?

Lets update the code above to reuse Select component

import { useField, useFieldState } from 'formular'

const FormularInput = ({ field }) => {
  const state = useFieldState(field)

  return <CustomInput value={state.value} onChange={field.set} />
}

const Auth = () => {
  const emailField = useField()
  const passwordField = useField()

  return (
    <>
      <FormularInput field={emailField} />
      <FormularInput field={passwordField} />
    </>
  )
}

Let's add validators and submit logic

const required = (value) => {
  if (!value) {
    return 'Required'
  }
}

const Auth = () => {
  const emailField = useField({
    validate: [ required ],
  })
  const passwordField = useField({
    validate: [ required ],
  })

  const handleSubmit = useCallback(async () => {
    const isEmailValid = await emailField.validate()
    const isPasswordValid = await passwordField.validate()
    
    const emailValue = emailField.state.value
    const passwordValue = passwordField.state.value
    
    const emailError = emailField.state.error
    const passwordError = passwordField.state.error
  }, [])

  return (
    <>
      <FormularInput field={emailField} />
      <FormularInput field={passwordField} />
      <button onClick={handleSubmit}>Login</button>
    </>
  )
}

Same could be written using useForm

const Auth = () => {
  const form = useForm({
    fields: {
      email: [ required ],
      password: [ required ],
    },
  })

  const handleSubmit = useCallback(async () => {
    const isValid = await form.validate()
    
    const values = form.getValues() // { email: '', password: '' }
    const errors = form.getErrors() // { email: 'Required', password: 'Required' }
  }, [])

  return (
    <>
      <FormularInput field={emailField} />
      <FormularInput field={passwordField} />
      <button onClick={handleSubmit}>Login</button>
    </>
  )
}

in most cases you need submit

const handleSubmit = useCallback(async () => {
  try {
    const values = await form.submit() // { email: '', password: '' }
  }
  catch (errors) {} // { email: 'Required', password: 'Required' }
}, [])

Validation

const required = (value) => {
  if (!value) {
    return 'Required'
  }
}

const uniqueEmail = async (value) => {
  const isExist = await fetch(`check-email-exist?email={value}`)
  
  if (isExists) {
    return 'Account with such email already exists'
  }
}

const field = useField({
  validate: [ required, uniqueEmail ]
})

const isValid = await field.validate()

☝️ field.validate() always async!
☝️ a validator function should return undefined if value is valid

Examples

• Basics
• Building own Input
• Async validation

Options

Form

type FormOpts = {
  name?: string
  fields: {
    [key: string]: FieldOpts
  }
  initialValues?: object
}

Field

type FieldOpts = {
  name?: string
  value?: string                // initial value
  validate?: Array<Function>    // list of validators
  readOnly?: boolean
  validationDelay?: number      // adds debounce to validation
}

Interfaces

Form

type FormEntity = {
  name?: string
  opts: FormOpts
  fields: {
    [key: string]: Field
  }
  state: {
    isValid: boolean
    isChanged: boolean
    isValidating: boolean
    isSubmitting: boolean
    isSubmitted: boolean
  }
  setState(values: Partial<State>): void
  setValues(values: object): void
  getValues(): object
  unsetValues(): void
  getErrors(): object
  async validate(): Promise<boolean>
  async submit(): Promise<object>
  on(eventName: string, handler: Function): void
  off(eventName: string, handler: Function): void
}

const form: FormEntity = useForm(opts)

Field

type FieldEntity = {
  form?: Form
  name?: string
  opts: FieldOpts
  node?: HTMLElement
  validators: Array<Function>
  readOnly: boolean
  debounceValidate: Function  // method to call validation with debounce
  state: {
    value: any
    error: any
    isChanged: boolean
    isValidating: boolean
    isValidated: boolean
    isValid: boolean
  }
  setState(values: Partial<State>): void
  setRef(node: HTMLElement): void
  unsetRef(): void
  set(value: any, opts?: { silent: boolean }): void
  unset(): void
  validate = (): CancelablePromise
  on(eventName: string, handler: Function): void
  off(eventName: string, handler: Function): void
}

const field: FieldEntity = useField(opts)

Note: { silent: true } in field.set doesn't trigger events.

Events

Form

form.on('state change', (state) => {
  // triggers on a form's state change
})

form.on('change', (field) => {
  // triggers on a field change
})

form.on('blur', (field) => {
  // triggers on a field blurring
})

Field

form.on('state change', (state) => {
  // triggers on a field's state change
})

field.on('set', (value) => {
  // triggers on a value set
})

field.on('change', (value) => {
  // simlink to "set"
})

field.on('unset', () => {
  // triggers on a value unset
})

field.on('start validate', () => {
  // triggers on a validation start
})

field.on('validate', (error) => {
  // triggers on a validation finish
})

field.on('blur', () => {
  // triggers on a field blurring
})