Formula Lifecycle


To create your form instance call the formula() method, this creates a form instance that can be attached to any element with the use directive.

When using like this, on component destruction the form will automatically unbind

import { formula } from 'svelte-formula';
const { form } = formula()
<!-- Use with a form element to get access to submission values -->
<form use:form></form>
<!-- Use on any other element to create reactive components -->
<div use:form></div>


Any Formula instance can be updated using the updateForm method, which accepts a new FormulaOptions object. When using update all existing handlers will be removed and rebound.

import { formula } from 'svelte-formula';
import { getMessges } from './libs/lang'
const { form, updateForm } = formula();
function switchLanguage(lang) {
const messages = getMessges(lang);
updateForm({ messages });
<div class='lang-switcher'>
<button on:click={() => switchLanguage('en')}>English</button>
<button on:click={() => switchLanguage('nl')}>Nederlands</button>
<button on:click={() => switchLanguage('fr')}>Français</button>
<form use:form>


The resetForm can be called at any time during the life of the form, it will reset the form to it's initial state after defaultValues and element values have been applied, also touched and dirty stores are reset.

import {formula} from 'svelte-formula';
const {form, $formValues, initialValues, formReset } = formula();
$: initialTotal = (initialValues?.value1 || 0) + (initialValues?.value2 || 0)
$: total = ($formValues?.value1 || 0) + ($formValues?.value2 || 0)
<form use:form>
<label for='value-1'>Value 1</label>
<input type='number' required id='value-1' name='value1' />
<label for='value-2'>Value 2</label>
<input type='number' required id='value-2' name='value2' />
<div>{$initialTotal?.value1} + {$initialTotal?.value2} = {initialTotal}</div>
<div>{$formValues?.value1} + {$formValues?.value2} = {total}</div>
<button on:click!preventDefault={() => formReset}>Reset</button>


The destroyForm method allows the form to be destroyed early, which removes all handlers and removes the stores from the global store.