Checkbox Group | Vielzeug

bit-checkbox-group is a form-associated fieldset wrapper for bit-checkbox items. It owns the selection state for all child checkboxes, mirrors that state into the values attribute as a comma-separated string, and submits that string under the group's name in native forms and bit-form.

Features

Form-associated group submission through name
Comma-separated values state for preselection and controlled updates
Propagation of color, size, and disabled to child bit-checkbox elements
fieldset and legend semantics with helper and error text wiring
Vertical and horizontal layouts

Source Code

View Checkbox Group Source

import {
  define,
  computed,
  createContext,
  createId,
  effect,
  html,
  inject,
  provide,
  type ReadonlySignal,
  signal,
} from '@vielzeug/craftit';
import { createChoiceFieldControl } from '@vielzeug/craftit/controls';

import type { ComponentSize, ThemeColor } from '../../types';

import { colorThemeMixin, disabledStateMixin, sizeVariantMixin } from '../../styles';
import { disablableBundle, sizableBundle, themableBundle, type PropBundle } from '../shared/bundles';
import { mountFormContextSync } from '../shared/dom-sync';
import { FORM_CTX } from '../shared/form-context';
import { createChoiceChangeDetail, type ChoiceChangeDetail } from '../shared/utils';
import componentStyles from './checkbox-group.css?inline';

// ─── Context ──────────────────────────────────────────────────────────────────

export type CheckboxGroupContext = {
  color: ReadonlySignal<ThemeColor | undefined>;
  disabled: ReadonlySignal<boolean>;
  size: ReadonlySignal<ComponentSize | undefined>;
  toggle: (value: string, originalEvent?: Event) => void;
  values: ReadonlySignal<string[]>;
};

export const CHECKBOX_GROUP_CTX = createContext<CheckboxGroupContext>('CheckboxGroupContext');

// ─── Types ────────────────────────────────────────────────────────────────────

export type BitCheckboxGroupProps = {
  /** Theme color — propagated to all child bit-checkbox elements */
  color?: ThemeColor;
  /** Disable all checkboxes in the group */
  disabled?: boolean;
  /** Error message shown below the group */
  error?: string;
  /** Helper text shown below the group */
  helper?: string;
  /** Legend / label for the fieldset. Required for accessibility. */
  label?: string;
  /** Form field name used during submission */
  name?: string;
  /** Layout direction of the checkbox options */
  orientation?: 'vertical' | 'horizontal';
  /** Mark the group as required */
  required?: boolean;
  /** Size — propagated to all child bit-checkbox elements */
  size?: ComponentSize;
  /** Comma-separated list of currently checked values */
  values?: string;
};

export type BitCheckboxGroupEvents = {
  change: ChoiceChangeDetail;
};

const checkboxGroupProps = {
  ...themableBundle,
  ...sizableBundle,
  ...disablableBundle,
  error: '',
  helper: '',
  label: '',
  name: '',
  orientation: 'vertical',
  required: false,
  values: '',
} satisfies PropBundle<BitCheckboxGroupProps>;

/**
 * A fieldset wrapper that groups `bit-checkbox` elements, provides shared
 * `color` and `size` via context, and manages multi-value selection state.
 *
 * @element bit-checkbox-group
 *
 * @attr {string} label - Legend text (required for a11y)
 * @attr {string} values - Comma-separated list of checked values
 * @attr {boolean} disabled - Disable all checkboxes in the group
 * @attr {string} error - Error message
 * @attr {string} helper - Helper text
 * @attr {string} name - Form field name
 * @attr {string} color - Theme color
 * @attr {string} size - Component size: 'sm' | 'md' | 'lg'
 * @attr {string} orientation - Layout: 'vertical' | 'horizontal'
 * @attr {boolean} required - Required field
 *
 * @fires change - Emitted when selection changes. detail: { value: string, values: string[], labels: string[], originalEvent?: Event }
 *
 * @slot - Place `bit-checkbox` elements here
 */
export const CHECKBOX_GROUP_TAG = define<BitCheckboxGroupProps, BitCheckboxGroupEvents>('bit-checkbox-group', {
  formAssociated: true,
  props: checkboxGroupProps,
  setup({ emit, host, props, slots }) {
    const formCtx = inject(FORM_CTX, undefined);

    mountFormContextSync(host.el, formCtx, props);

    const choice = createChoiceFieldControl<string>({
      context: formCtx,
      disabled: props.disabled,
      error: props.error,
      getValue: (value) => value,
      helper: props.helper,
      label: props.label,
      mapControlledValue: (value) => value,
      multiple: signal(true),
      name: props.name,
      prefix: 'checkbox-group',
      value: props.values,
    });
    const checkedValues = choice.selectedItems;

    const getCheckboxes = (): HTMLElement[] =>
      Array.from(host.el.getElementsByTagName('bit-checkbox')) as HTMLElement[];
    const getLabelForValue = (value: string): string => {
      const checkbox = getCheckboxes().find((item) => (item.getAttribute('value') ?? '') === value);

      return checkbox?.textContent?.replace(/\s+/g, ' ').trim() || value;
    };
    const emitChange = (originalEvent?: Event) => {
      const values = checkedValues.value;

      emit('change', createChoiceChangeDetail(values, values.map(getLabelForValue), originalEvent));
    };

    const toggleCheckbox = (val: string, originalEvent?: Event) => {
      choice.toggleItem(val);
      host.el.setAttribute('values', choice.formValue.value);
      choice.triggerValidation('change');
      emitChange(originalEvent);
    };

    provide(CHECKBOX_GROUP_CTX, {
      color: props.color,
      disabled: computed(() => Boolean(props.disabled.value)),
      size: props.size,
      toggle: toggleCheckbox,
      values: checkedValues,
    });

    // Sync checked state + color/size/disabled onto slotted bit-checkbox children
    const syncChildren = () => {
      const values = checkedValues.value;
      const color = props.color.value;
      const size = props.size.value;
      const disabled = props.disabled.value;
      const checkboxes = Array.from(host.el.getElementsByTagName('bit-checkbox')) as HTMLElement[];

      for (const checkbox of checkboxes) {
        const val = checkbox.getAttribute('value') ?? '';

        if (values.includes(val)) checkbox.setAttribute('checked', '');
        else checkbox.removeAttribute('checked');

        if (color) checkbox.setAttribute('color', color);
        else checkbox.removeAttribute('color');

        if (size) checkbox.setAttribute('size', size);
        else checkbox.removeAttribute('size');

        if (disabled) checkbox.setAttribute('disabled', '');
        else checkbox.removeAttribute('disabled');
      }
    };

    effect(() => {
      void slots.elements().value;
      syncChildren();
    });

    effect(() => {
      void slots.elements().value;

      const listeners = getCheckboxes().map((checkbox) => {
        const handler = (event: Event) => {
          event.stopPropagation();

          const val = (checkbox.getAttribute('value') ?? '').trim();

          if (!val) return;

          toggleCheckbox(val, event);
        };

        checkbox.addEventListener('change', handler);

        return () => {
          checkbox.removeEventListener('change', handler);
        };
      });

      return () => {
        for (const dispose of listeners) dispose();
      };
    });

    const legendId = createId('checkbox-group-legend');
    const errorId = `${legendId}-error`;
    const helperId = `${legendId}-helper`;
    const hasError = computed(() => Boolean(props.error.value));
    const hasHelper = computed(() => Boolean(props.helper.value) && !hasError.value);

    return html`
      <fieldset
        role="group"
        aria-required="${() => String(Boolean(props.required.value))}"
        aria-invalid="${() => String(hasError.value)}"
        aria-errormessage="${() => (hasError.value ? errorId : null)}"
        aria-describedby="${() => (hasError.value ? errorId : hasHelper.value ? helperId : null)}">
        <legend id="${legendId}" ?hidden=${() => !props.label.value}>
          ${() => props.label.value}${() => (props.required.value ? html`<span aria-hidden="true"> *</span>` : '')}
        </legend>
        <div class="checkbox-group-items" part="items">
          <slot></slot>
        </div>
        <div class="error-text" id="${errorId}" role="alert" ?hidden=${() => !hasError.value}>
          ${() => props.error.value}
        </div>
        <div class="helper-text" id="${helperId}" ?hidden=${() => !hasHelper.value}>${() => props.helper.value}</div>
      </fieldset>
    `;
  },
  styles: [colorThemeMixin, sizeVariantMixin(), disabledStateMixin(), componentStyles],
});

Basic Usage

html

<bit-checkbox-group label="Interests" values="sport,music">
  <bit-checkbox value="sport">Sport</bit-checkbox>
  <bit-checkbox value="music">Music</bit-checkbox>
  <bit-checkbox value="travel">Travel</bit-checkbox>
</bit-checkbox-group>

<script type="module">
  import '@vielzeug/buildit/checkbox-group';
  import '@vielzeug/buildit/checkbox';
</script>

Form Submission

Set name on the group when you want its selected values to submit with a form. The submitted value is a comma-separated string such as email,sms.

html

<bit-form id="prefs-form" novalidate>
  <bit-checkbox-group name="contact" label="Preferred contact" values="email,sms">
    <bit-checkbox value="email">Email</bit-checkbox>
    <bit-checkbox value="phone">Phone</bit-checkbox>
    <bit-checkbox value="sms">SMS</bit-checkbox>
  </bit-checkbox-group>
  <bit-button type="submit">Save Preferences</bit-button>
</bit-form>

<script type="module">
  import '@vielzeug/buildit/form';
  import '@vielzeug/buildit/checkbox-group';
  import '@vielzeug/buildit/checkbox';
  import '@vielzeug/buildit/button';

  document.getElementById('prefs-form').addEventListener('submit', (e) => {
    console.log('contact:', e.detail.formData.get('contact'));
  });
</script>

Orientation

html

<bit-checkbox-group label="Notifications (vertical)">
  <bit-checkbox value="email">Email</bit-checkbox>
  <bit-checkbox value="push">Push</bit-checkbox>
  <bit-checkbox value="sms">SMS</bit-checkbox>
</bit-checkbox-group>

<bit-checkbox-group label="Working days (horizontal)" orientation="horizontal" values="mon,wed,fri">
  <bit-checkbox value="mon">Mon</bit-checkbox>
  <bit-checkbox value="tue">Tue</bit-checkbox>
  <bit-checkbox value="wed">Wed</bit-checkbox>
  <bit-checkbox value="thu">Thu</bit-checkbox>
  <bit-checkbox value="fri">Fri</bit-checkbox>
</bit-checkbox-group>

Validation Feedback

html

<bit-checkbox-group label="Interests" helper="Select all that apply.">
  <bit-checkbox value="sport">Sport</bit-checkbox>
  <bit-checkbox value="music">Music</bit-checkbox>
  <bit-checkbox value="travel">Travel</bit-checkbox>
</bit-checkbox-group>

<bit-checkbox-group label="Agreements" error="Please accept all required policies." color="error">
  <bit-checkbox value="terms">I accept the terms of service</bit-checkbox>
  <bit-checkbox value="privacy">I accept the privacy policy</bit-checkbox>
</bit-checkbox-group>

API Reference

label: string, default ''. Legend text used as the group's accessible name.
values: string, default ''. Comma-separated currently checked values.
name: string, default ''. Form field name used during submission.
orientation: 'vertical' | 'horizontal', default 'vertical'. Layout direction of options.
color: 'primary' | 'secondary' | 'info' | 'success' | 'warning' | 'error'. Propagated to child checkboxes.
size: 'sm' | 'md' | 'lg'. Propagated to child checkboxes.
disabled: boolean, default false. Disables all checkboxes in the group.
required: boolean, default false. Marks the group as required for accessibility and validation.
error: string, default ''. Error message shown below the group.
helper: string, default ''. Helper text shown below the group when no error is present.

Events

Event	Detail	Description
`change`	`{ values: string[] }`	Full array of currently checked values after any toggle

Best Practices

Put name on the group instead of individual child checkboxes when you want one submitted field.
Update values, not child checked attributes, when you want to control the group from outside.
Use bit-radio-group instead when the user must pick exactly one option.

Usage Guide

Framework Integration

Theming

Examples

Features

Source Code

Basic Usage

Form Submission

Orientation

Validation Feedback

API Reference

Events

Best Practices

Features ​

Source Code ​

Basic Usage ​

Form Submission ​

Orientation ​

Validation Feedback ​

API Reference ​

Events ​

Best Practices ​

Features

Source Code

Basic Usage

Form Submission

Orientation

Validation Feedback

API Reference

Events

Best Practices