Svelte HTML5 Validators

Simple library that adds validator attributes --required, min, maxlength...-- to form elements using Svelte. By directly adding these attributes to the form elements, the native HTML5 validation controls can be used. That includes the pseudo-classes valid and invalid to style form elements according to its validity status.

Install

npm i svelte-html5-validators
or
yarn add svelte-html5-validators

How to use

<script>
  import { buildForm } from "svelte-html5-validators";

  const { form, applyValidators } = buildForm({ 
    "name": ["required", "pattern:^[A-Z][a-zA-Z\\s]*$"],
  }, { initialValidation: true, validateOnChange: true });

  let formData = {
    name: "world"
  };
</script>

<style type="text/scss">
  input {
    &:invalid {
      border: 2px dashed red;
    }

    &:valid {
      border: 2px solid black;
    }
  }
</style>

<form use:applyValidators>
  <input
    type="text"
    name="name"
    bind:value={formData.name} />
</form>

API

buildForm(validators: FieldValidators, config: Config = {}): { form: Form; applyValidators: SvelteAction }

Returns a Form object and the applyValidators action, which uses the validators given as the first parameters.

As second parameter you can pass a configuration object. The possible options are as follow:

Property	Description	Default
initialValidation	Set to true if you want to perform an initial validation check	true
validateOnChange	Set to true if you want to perform a validation check after every input	true

applyValidators: SvelteAction

A Svelte action to use on the form HTML element. Finds all the form elements (input, textarea, select) and adds the validators given to buildForm.

It is necessary to give to all the form elements, or at least to the ones where you want to apply validators, an id or name attribute. In either case, there exists a form element and a validator for it is not provided or a validator is defined for a not added form element, applyValidators will not error out.

Field Validators Object

Object to be provided to the buildForm function. The properties for this object are the form elements id or name attributes, and the assigned value to each property is a string array with the validators.
The validators that require a value (e.g.: min) are on the form min:6.

{ "name": ["required", "minlength:6"], "age": ["min:0", "max:99"] }

<input type="text" name="name" />
<input type="number" name="age" />

Form Object

Svelte store returned by the buildForm function. This store provides the object value, the getControl function, and the validate function.

Value

{
  entries: {
    name: string;
    value: any;
    valid: boolean;
  }[];
  valid: boolean
}

entries is an array of objects. Each entry has name, the control name of the form element; value, the value of the form element; and valid, the validity of the form element.
valid indicates the entire form validity.

getControl: (formControlName: string) => { name: string; value: any; valid: boolean }

Returns the entry of the given formControlName of the form object.

validate: () => void

Checks the validity of the form and updates the form object with the current form data.

clear: () => void

Clears the form object --undefines the values from each entry-- and invalidates each entry and the form. If you want to check if the form object is valid after clearing it, you will need to execute validate.

Validators

required

{ "control": ["required"] }

Adds the attribute required to the form element with id or name control.
Valid when it has some value.

disabled

{ "control": ["disabled"] }

Adds the attribute disabled to the form element with id or name control.
Blocks editing of the form element.

pattern

{ "control": ["pattern:^[A-Z][a-zA-Z\\s]*$"] }

Adds the attribute pattern with the pattern given after the : to the form element with id or name control.
Valid when the value matches the pattern.

min

{ "control": ["min:3"] }

Adds the attribute min with the given argument to the form element with id or name control.
Valid for inputs of type range, number, date, month, week, datetime, datetime-local, and time when the value is higher than the given argument.

max

{ "control": ["max:30"] }

Adds the attribute max with the given argument to the form element with id or name control.
Valid for inputs of type range, number, date, month, week, datetime, datetime-local, and time when the value is lower than the given argument.

minlength

{ "control": ["minlength:3"] }

Adds the attribute minlength with the given argument to the form element with id or name control.
Valid for inputs of type text, search, url, tel, email, password, and also on textareas when the number of characters is larger than the given argument.

maxlength

{ "control": ["maxlength:30"] }

Adds the attribute maxlength with the given argument to the form element with id or name control.
Valid for inputs of type text, search, url, tel, email, password, and also on textareas when the number of characters is smaller than the given argument.

datetime

{ "control": ["datetime"] }

Sets the input's attribute type with id or name control to datetime-local.
Valid when the value is a datetime.

datetime-local

{ "control": ["datetime-local"] }

Sets the input's attribute type with id or name control to datetime-local.
Valid when the value is a datetime.

date

{ "control": ["date"] }

Sets the input's attribute type with id or name control to date.
Valid when the value is a date.

time

{ "control": ["time"] }

Sets the input's attribute type with id or name control to time.
Valid when the value is a time.

month

{ "control": ["month"] }

Sets the input's attribute type with id or name control to month.
Valid when the value is a month.

week

{ "control": ["week"] }

Sets the input's attribute type with id or name control to week.
Valid when the value is a week.

email

{ "control": ["email"] }

Sets the input's attribute type with id or name control to email.
Valid when the value is an e-mail address.

tel

{ "control": ["tel"] }

Sets the input's attribute type with id or name control to tel.
Valid when the value is a telephone number.

url

{ "control": ["url"] }

Sets the input's attribute type with id or name control to url.
Valid when the value is an URL.

password

{ "control": ["password"] }

Sets the input's attribute type with id or name control to password.
Hides the value of the form element.