Checkbox Group

lion-checkbox-group component enhances the functionality of the native <input type="checkbox"> element. Its purpose is to provide a way for users to check multiple options amongst a set of choices, or to function as a single toggle.

You should use lion-checkbox elements as the children of the <lion-checkbox-group>.

import { html } from 'lit-html';
import { Required, Validator } from '@lion/form-core';
import { loadDefaultFeedbackMessages } from '@lion/validate-messages';
import './lion-checkbox-group.js';
import './lion-checkbox.js';

export default {
  title: 'Forms/Checkbox Group',
};

loadDefaultFeedbackMessages();

export const main = () => html`
  <lion-checkbox-group name="scientists[]" label="Favorite scientists">
    <lion-checkbox label="Archimedes" .choiceValue=${'Archimedes'}></lion-checkbox>
    <lion-checkbox label="Francis Bacon" .choiceValue=${'Francis Bacon'}></lion-checkbox>
    <lion-checkbox label="Marie Curie" .choiceValue=${'Marie Curie'}></lion-checkbox>
  </lion-checkbox-group>
`;

Make sure that the checkbox-group also has a name attribute, this is necessary for the lion-form's serialization result.

Live Demo/Documentation

See our storybook for a live demo and API documentation

Features

Since it extends from lion-fieldset, it has all the features a fieldset has.

How to use

Installation

npm i --save @lion/checkbox-group

import '@lion/checkbox-group/lion-checkbox-group.js';
import '@lion/checkbox-group/lion-checkbox.js';

Model value

The modelValue of a lion-checkbox-group is an array containing the choiceValues of the lion-checkbox elements that have been checked.

Given the scientists example above, say that we were to select the first and last options (Archimedes & Marie Curie).

Then the modelValue of the lion-checkbox-group will look as follows:

const groupElement = [parent].querySelector('lion-checkbox-group');
groupElement.modelValue;
  => ["Archimedes", "Marie Curie"];

The `name` attribute

The name attribute of a lion-checkbox-group automatically gets assigned to its lion-checkbox children. You can also specify names for the lion-checkbox elements, but if this name is different from the name assigned to lion-checkbox-group, then an exception will be thrown.

Our recommendation would be to set the name attribute only on the lion-checkbox-group and not on the lion-checkbox elements.

Example

<lion-checkbox-group
  name="scientists[]"
  label="Favorite scientists"
>
  <lion-checkbox label="Archimedes" .choiceValue=${'Archimedes'}></lion-checkbox>
  <lion-checkbox label="Francis Bacon" .choiceValue=${'Francis Bacon'}></lion-checkbox>
  <lion-checkbox label="Marie Curie" .choiceValue=${'Marie Curie'}></lion-checkbox>
</lion-checkbox-group>

Pre-select

You can pre-select options by targeting the modelValue object of the option and setting the checked property to true.

export const preselect = () => html`
  <lion-checkbox-group name="scientists" label="Favorite scientists">
    <lion-checkbox label="Archimedes" .choiceValue=${'Archimedes'}></lion-checkbox>
    <lion-checkbox label="Francis Bacon" .choiceValue=${'Francis Bacon'} checked></lion-checkbox>
    <lion-checkbox
      label="Marie Curie"
      .modelValue=${{ value: 'Marie Curie', checked: true }}
    ></lion-checkbox>
  </lion-checkbox-group>
`;

Disabled

You can disable the entire group by setting the disabled attribute on the <lion-checkbox-group>.

export const disabled = () => html`
  <lion-checkbox-group name="scientists[]" label="Favorite scientists" disabled>
    <lion-checkbox label="Archimedes" .choiceValue=${'Archimedes'}></lion-checkbox>
    <lion-checkbox label="Francis Bacon" .choiceValue=${'Francis Bacon'}></lion-checkbox>
    <lion-checkbox
      label="Marie Curie"
      .modelValue=${{ value: 'Marie Curie', checked: true }}
    ></lion-checkbox>
  </lion-checkbox-group>
`;

Validation

You can apply validation to the <lion-checkbox-group>, similar to how you would do so in any fieldset. The interaction states of the <lion-checkbox-group> are evaluated in order to hide or show feedback messages.

export const validation = () => {
  const validate = () => {
    const checkboxGroup = document.querySelector('#scientists');
    checkboxGroup.submitted = !checkboxGroup.submitted;
  };
  return html`
    <lion-checkbox-group
      id="scientists"
      name="scientists[]"
      label="Favorite scientists"
      .validators=${[new Required()]}
    >
      <lion-checkbox label="Archimedes" .choiceValue=${'Archimedes'}></lion-checkbox>
      <lion-checkbox label="Francis Bacon" .choiceValue=${'Francis Bacon'}></lion-checkbox>
      <lion-checkbox label="Marie Curie" .choiceValue=${'Marie Curie'}></lion-checkbox>
    </lion-checkbox-group>
    <button @click="${() => validate()}">Validate</button>
  `;
};

Validation advanced

Below is a more advanced validator on the group that evaluates the children checkboxes' checked states.

export const validationAdvanced = () => {
  class HasMinTwoChecked extends Validator {
    execute(value) {
      return value.length < 2;
    }
    static get validatorName() {
      return 'HasMinTwoChecked';
    }
    static async getMessage() {
      return 'You need to select at least 2 values.';
    }
  }
  const validate = () => {
    const checkboxGroup = document.querySelector('#scientists2');
    checkboxGroup.submitted = !checkboxGroup.submitted;
  };
  return html`
    <lion-checkbox-group
      id="scientists2"
      name="scientists[]"
      label="Favorite scientists"
      help-text="You should have at least 2 of those"
      .validators=${[new Required(), new HasMinTwoChecked()]}
    >
      <lion-checkbox label="Archimedes" .choiceValue=${'Archimedes'}></lion-checkbox>
      <lion-checkbox label="Francis Bacon" .choiceValue=${'Francis Bacon'}></lion-checkbox>
      <lion-checkbox label="Marie Curie" .choiceValue=${'Marie Curie'}></lion-checkbox>
    </lion-checkbox-group>
    <button @click="${() => validate()}">Validate</button>
  `;
};

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