Forms

Form controller for native HTML forms, React, Vue, Svelte, and direct browser usage.

Table of Contents

• Installation
• CDN / Browser
• Entrypoints
• Quick Start
• What You Can Do
• API Reference
• Examples
• Documentation
• License

Installation

npm install @samline/forms

pnpm add @samline/forms

yarn add @samline/forms

bun add @samline/forms

CDN / Browser

Use the browser build when you do not have a bundler and need to run the package directly in HTML.

<script src="https://unpkg.com/@samline/[email protected]/dist/browser/global.global.js"></script>

Pin the version in production.

The browser build exposes window.forms.

<form id="contact-form">
  <input name="email" type="email" />
</form>

<script src="https://unpkg.com/@samline/[email protected]/dist/browser/global.global.js"></script>
<script>
  const contactForm = window.forms.form('contact-form')
  contactForm.validate()
</script>

Entrypoints

| Entrypoint | Use | | --- | --- | | @samline/forms | Main vanilla API | | @samline/forms/core | Types, serialization, and validation | | @samline/forms/vanilla | Explicit DOM API entrypoint | | @samline/forms/react | React hook | | @samline/forms/vue | Vue composable | | @samline/forms/svelte | Svelte store and action | | @samline/forms/browser | Browser global bundle |

Quick Start

import { form } from '@samline/forms'

const contactForm = form('contact-form', {
  validators: {
    email: {
      required: true,
      pattern: /^[^\s@]+@[^\s@]+\.[^\s@]+$/
    }
  }
})

contactForm.onSubmit((element, data, formData, state) => {
  console.log(element, data, formData, state)
})

What You Can Do

• bind to a form by id, element, or ref-like target
• read and write field values
• serialize form values to both a plain object and FormData
• watch individual fields and subscribe to global form state
• prefill values from the current URL query string
• mark filled and error states through DOM attributes for styling
• run built-in validation rules and custom validators
• trigger submit handlers with optional auto-submit behavior
• reset, inspect, and destroy the controller cleanly

API Reference

form(target, options)

Creates a controller from:

• a form id string
• a real HTMLFormElement
• a ref-like object with current

Properties

• element: the bound HTMLFormElement | null
• f: alias of element
• options: normalized controller options

Submission

• onSubmit(callback, preventDefault?)
• autoSubmit(options?)
• disableAutoSubmit()

onSubmit accepts an optional second argument named preventDefault.

• onSubmit(callback) is equivalent to onSubmit(callback, true)
• with true, valid submissions are intercepted, which is the right choice for fetch or AJAX flows
• with false, valid submissions continue with the browser's native form submit behavior
• invalid submissions are still prevented, even when you pass false

Field observation

• watch(field, callback)
• observe(field, callback)
• subscribe(listener)
• unwatch(field?, callback?)

Field values

• setValue(name, value)
• getValue(name)
• getField(name)
• prefill(fieldName?)

Validation and errors

• validate(fields?)
• revalidate(fields?)
• setErrors(fields)
• clearErrors(fields?)

Manual errors created with setErrors() are cleared per field by default as soon as that field changes, including updates triggered through setValue(). Pass clearManualErrorsOnChange: false to keep manual errors until you clear them explicitly.

Form lifecycle and state

• getData()
• getState()
• append(options)
• reset()
• destroy()

Validation options

Built-in rules supported through validators:

• required
• minLength
• maxLength
• pattern
• validate for custom callbacks

Controller options also include:

• autoValidate to validate on initialization and subsequent field changes
• clearErrorsOnSubmit to reset manual errors before submit validation runs
• clearManualErrorsOnChange to clear only the changed field's manual error before the normal validation flow continues

const profileForm = form('profile-form', {
  clearManualErrorsOnChange: false
})

Examples

Bind by id

import { form } from '@samline/forms'

const profileForm = form('profile-form')

Bind by element

const element = document.querySelector('#profile-form') as HTMLFormElement
const profileForm = form(element)

Watch a field

const profileForm = form('profile-form')

profileForm.watch('email', value => {
  console.log('email changed:', value)
})

Validate with built-in rules

const profileForm = form('profile-form', {
  validators: {
    email: {
      required: true,
      pattern: /^[^\s@]+@[^\s@]+\.[^\s@]+$/
    },
    password: {
      minLength: 8
    }
  }
})

const result = profileForm.validate()
console.log(result.isValid, result.errors)

Submit with fetch

const profileForm = form('profile-form')

profileForm.onSubmit(async (_element, _data, formData) => {
  await fetch('/api/profile', {
    method: 'POST',
    body: formData
  })
})

This uses the default preventDefault = true, so the package intercepts the valid submit and lets you handle the request yourself.

Submit with native form behavior

const profileForm = form('profile-form')

profileForm.onSubmit(() => {
  console.log('validation passed')
}, false)

Use false when the form should continue with its normal HTML submission after validation succeeds, for example in server-rendered applications such as Laravel with Blade.

If validation fails, the package still prevents the submit.

Prefill from the URL

const profileForm = form('profile-form')
profileForm.prefill()

Work with form state

const profileForm = form('profile-form')

const unsubscribe = profileForm.subscribe(state => {
  console.log(state.values)
  console.log(state.errors)
})

unsubscribe()

Documentation

• docs/vanilla.md
• docs/react.md
• docs/vue.md
• docs/svelte.md
• docs/browser.md

License

MIT