svelte-formula

Svelte Formula

Formula is a zero-configuration reactive form library for Svelte, currently in early development.

This library uses HTML form attributes to do validation, and works with the localised message from the browser.

Install Instructions

npm i svelte-formula

Usage

To use Formula, create the directive and store values by calling the formula() method in the library, this returns the form action and the available stores.

Options

While the library is zero-configuration it does support options which can be passed as an object to the formula constructor method.

Options	Type	Description
local	string	Optional locale for id sorting when using multiple values

Example

The form action can be used with any element and not just <form> elements - it checks for all child form elements that have a name attribute and return some kind of validity. If used with a form element it will provide values on submit, as well as the current value of the form.

<script>
  import { onDestroy } from 'svelte'
  import { formula } from 'svelte-formula'

  const { form, formValues, submitValues, validity, touched, formValid } = formula();

  const valueSub = formValues.subscribe(values => console.log(values));
  const submitSub = submitValues.subscribe(values => console.log(values));

  function handleSubmit(e) {
    e.preventDefault();
  }

  onDestroy(() => {
    valueSub();
    submitSub();
  })

</script>

<form use:form on:submit={handleSubmit}>
  <div class='form-field'>
    <label for='username'>Username</label>
    <input type='text' id='username' name='username' required />
    <span hidden={$validity?.username?.valid}>{ validity?.username?.message }</span>
  </div>
  <div class='form-field'>
    <label for='password'>Password</label>
    <input type='password' id='password' name='password' required minlength='8' />
    <span hidden={$validity?.password?.valid}>{ validity?.password?.message }</span>
  </div>

  <button disabled={!$formValid}>Save</button>
</form>

Stores

formValues

The formValues store can be subscribed to and will emit every time the user types into, or blurs off from a field. The value is a Object that contains a key/value map of all form fields with the key being the name property of the element

submitValues

Similar to the formValues object, the subscription only emits when a form submit event occurs, and only emits when using a <form> element

validity

A store that contains a key/value Object where again the key is the name property. The value is another object with the following properties

• valid - Boolean - If the field is valid
• invalid - Boolean - if the field is invalid
• message - String - The message returned from the HTML validity
• errors - Object - A map of errors that are true returned by the Constraint Validation API.

formValid

A store that is a single Boolean value if the form is currently valid or not - this only emits when the form validity changes

touched

A store that updates when fields are marked as touched - contains an Object with key/value of name and Boolean, fields are added to the store as they receive a focus event

dirty

A store that updates when fields are marked as dirty - contains an Object with key/value of name and Boolean, fields where the user triggers a blur event, and the value has been changed from the original value.

Roadmap

Field Type Support

• Support Basic Input fields (text, number, password, email, url) as text values
  • Support multiple named fields with unique id attributes, with an array of results sorted by ID alphabetically
  • Return correct value type for fields (return number as Number value)
• Support Select Fields
  • Support Multiple Select Fields
• Support Radio Fields
• Support Checkbox Fields
  • Support Multiple Checkbox Fields
• Support the Range input
• Support the Color input
• Support the Date / Time / DateTime inputs
• Support the File input

Other Items

• Add Unit Tests
• Add full documentation

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Changelog

[0.1.1] 2021-02-15

Added

• First config option for formula - allowing the locale for sorting to be overridden if you don't want to use the users own locale

• Support for multiple input types that are not checkboxes (e.g text, number, etc) - when using this each input with the same name REQUIRES and id property. Returns an array sorted on the id property alphabetically in the users' locale if detected (and always falls back to en if not), if this needs to be overridden it can be passed to the formula constructor (e.g formula({ locale: 'de' });)