Alert

A feedback banner for surface-level status messages — errors, warnings, successes, and informational notices. Supports an optional heading, icon, metadata, action buttons, and a dismiss button.

Features

• 🎨 3 Variants: flat (default), solid, bordered
• 🌈 6 Color Themes: primary, secondary, info, success, warning, error
• 📏 3 Sizes: sm, md, lg
• ✖️ Dismissible: animated close button — plays a smooth fade+collapse animation before hiding
• 🖼️ Icon Slot: prepend any SVG or icon font glyph
• 🏷️ Heading: optional bold heading above the message
• 🕐 Meta Slot: timestamp or secondary info alongside the heading
• 🔘 Actions Slot: call-to-action buttons below the message (or horizontal)
• 🎯 Accented: left accent border for flat and bordered variants
• ♿ Accessible: role="alert" + smart aria-live, labelled close button

Source Code

View Source Code

import { defineComponent, guard, html, onMount, onSlotChange, signal } from '@vielzeug/craftit';

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

import { closeIcon } from '../../icons';
import { forcedColorsMixin, formFieldMixins, sizeVariantMixin } from '../../styles';
import { awaitExit } from '../../utils/animation';
import componentStyles from './alert.css?inline';

export type BitAlertEvents = {
  dismiss: { originalEvent: MouseEvent };
};

export type BitAlertProps = {
  /** Show a left accent border (for flat/bordered variants) */
  accented?: boolean;
  /** Theme color */
  color?: ThemeColor;
  /** Show a dismissable (×) button */
  dismissible?: boolean;
  /** Heading text shown above the content */
  heading?: string;
  /** Position action buttons to the right instead of below */
  horizontal?: boolean;
  /** Border radius */
  rounded?: RoundedSize | '';
  /** Alert size */
  size?: ComponentSize;
  /** Visual style variant */
  variant?: 'solid' | 'flat' | 'bordered';
};

/**
 * A status/feedback banner with optional heading, icon slot, and dismiss button.
 *
 * @element bit-alert
 *
 * @attr {string} color - Theme color (primary/success/warning/error…)
 * @attr {string} variant - Visual style: 'flat' | 'solid' | 'bordered'
 * @attr {string} size - Size: 'sm' | 'md' | 'lg'
 * @attr {string} rounded - Border radius size
 * @attr {string} heading - Bold heading text above the content
 * @attr {boolean} dismissible - Show a close (×) button
 * @attr {boolean} accented - Add a left accent border (flat/bordered only)
 * @attr {boolean} horizontal - Position action buttons to the right instead of below
 *
 * @fires dismiss - Fired when the alert is dismissed
 *
 * @slot - Default slot for the alert message content
 * @slot icon - Icon on the left side
 * @slot meta - Metadata displayed alongside the heading (lighter, right-aligned)
 * @slot actions - Action buttons shown below the message
 *
 * @cssprop --alert-bg - Background color
 * @cssprop --alert-color - Text/icon color
 * @cssprop --alert-border-color - Border color
 * @cssprop --alert-radius - Border radius
 * @cssprop --alert-padding - Padding
 * @cssprop --alert-gap - Gap between icon, body, and close button
 * @cssprop --alert-font-size - Font size
 *
 * @example
 * ```html
 * <bit-alert color="success">Your changes have been saved.</bit-alert>
 * <bit-alert color="error" variant="solid" dismissible heading="Something went wrong">
 *   Please try again later.
 * </bit-alert>
 * ```
 */
export const ALERT_TAG = defineComponent<BitAlertProps, BitAlertEvents>({
  props: {
    accented: { default: false },
    color: { default: undefined },
    dismissible: { default: false },
    heading: { default: '' },
    horizontal: { default: false },
    rounded: { default: undefined },
    size: { default: undefined },
    variant: { default: undefined },
  },
  setup({ emit, host, props }) {
    const handleDismiss = guard(
      () => props.dismissible.value,
      (e: MouseEvent) => {
        host.setAttribute('dismissing', '');
        awaitExit(host, () => {
          host.removeAttribute('dismissing');
          host.setAttribute('dismissed', '');
          emit('dismiss', { originalEvent: e });
        });
      },
    );
    const hasIcon = signal(false);
    const hasActions = signal(false);

    onMount(() => {
      onSlotChange('icon', (els) => {
        hasIcon.value = els.length > 0;
      });
      onSlotChange('actions', (els) => {
        hasActions.value = els.length > 0;
      });
    });

    return html`
      <div class="alert" :role="${() => (props.color.value === 'error' ? 'alert' : 'status')}" part="alert">
        <span class="icon" part="icon" aria-hidden="true" ?hidden=${() => !hasIcon.value}>
          <slot name="icon"></slot>
        </span>
        <div class="header" part="header" ?hidden=${() => !props.heading.value}>
          <span class="heading" part="heading">${() => props.heading.value}</span>
          <span class="meta" part="meta">
            <slot name="meta"></slot>
          </span>
        </div>
        <div class="body" part="body">
          <div class="content" part="content">
            <slot></slot>
          </div>
        </div>
        <div class="actions" part="actions" ?hidden=${() => !hasActions.value}>
          <slot name="actions"></slot>
        </div>
        <button
          class="close"
          part="close"
          type="button"
          aria-label="Dismiss alert"
          ?hidden=${() => !props.dismissible.value}
          @click=${handleDismiss}>
          ${closeIcon}
        </button>
      </div>
    `;
  },
  styles: [
    ...formFieldMixins,
    forcedColorsMixin,
    sizeVariantMixin({
      lg: { '--_padding': 'var(--size-4) var(--size-5)', fontSize: 'var(--text-base)', gap: 'var(--size-3-5)' },
      sm: { '--_padding': 'var(--size-2) var(--size-3)', fontSize: 'var(--text-xs)', gap: 'var(--size-2)' },
    }),
    componentStyles,
  ],
  tag: 'bit-alert',
});

Basic Usage

<bit-alert color="success">Your changes have been saved.</bit-alert>

<script type="module">
  import '@vielzeug/buildit/alert';
</script>

Variants

Three visual styles are available via the variant attribute. flat is the default.

PreviewCode

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Colors

PreviewCode

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Sizes

PreviewCode

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Heading

Use heading to add a bold heading above the message body.

PreviewCode

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Dismissible

Add dismissible to show a close (×) button. When clicked, the component plays a bit-alert-exit animation (opacity fade + height collapse) before applying [dismissed] which sets display: none. Listen to the dismiss event to remove it from the DOM or restore it later.

PreviewCode

RTL

document.querySelector('bit-alert').addEventListener('dismiss', (e) => {
  e.target.remove(); // optionally remove from DOM entirely
});

Icon

Use the icon slot to add a leading icon. The icon wrapper is hidden entirely when the slot is empty — no reserved space.

PreviewCode

RTL

Meta

Use the meta slot to add secondary information (e.g. a timestamp) displayed alongside the heading in a lighter, smaller style. Pair it with a heading for best results.

PreviewCode

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Actions

Use the actions slot to add call-to-action buttons below the message.

PreviewCode

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Horizontal Actions

Add horizontal to move the actions to the right side of the content instead of below it. Best suited for short, single-line messages without a heading.

PreviewCode

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TIP

Avoid combining horizontal with heading — it makes the layout feel cramped.

Accented

Add accented to add a thick left border for extra visual emphasis. Only applies to flat and bordered variants.

PreviewCode

RTL

API Reference

Attributes

Attribute	Type	Default	Description
color	'primary' | 'secondary' | 'info' | 'success' | 'warning' | 'error'	—	Theme color
variant	'flat' | 'solid' | 'bordered'	'flat'	Visual style variant
size	'sm' | 'md' | 'lg'	'md'	Component size
rounded	'none' | 'sm' | 'md' | 'lg' | 'full'	—	Border radius override
heading	string	''	Bold heading above the message body
dismissible	boolean	false	Show a close (×) button
accented	boolean	false	Left accent border (flat/bordered variants only)
horizontal	boolean	false	Place action buttons beside the content

Slots

Slot	Description
(default)	Alert message content
icon	Icon on the leading edge. Hidden when empty — no reserved space.
meta	Secondary info alongside the heading (lighter, right-aligned, smaller)
actions	Action buttons below the message, or beside it when horizontal is set

Events

Event	Detail	Description
dismiss	{ originalEvent: MouseEvent }	Fired when the close button is clicked

CSS Parts

Part	Description
alert	Root container element
icon	Icon wrapper
body	Body flex container
header	Heading + meta row
heading	Heading text span
meta	Meta slot wrapper
content	Default slot wrapper
actions	Actions slot wrapper
close	Dismiss button

CSS Custom Properties

Property	Description	Default
--alert-bg	Background color	Theme-dependent
--alert-color	Text and icon color	Theme-dependent
--alert-border-color	Border color	Theme-dependent
--alert-radius	Border radius	var(--rounded-lg)
--alert-padding	Internal padding	var(--size-3) var(--size-4)
--alert-gap	Gap between icon, body, and close	var(--size-3)
--alert-font-size	Font size	var(--text-sm)

Accessibility

The alert component follows WAI-ARIA best practices.

bit-alert

✅ Screen Readers

• Uses role="alert" with aria-live="polite" — screen readers announce the alert on insertion.
• aria-live is assertive when color="error" so urgent errors interrupt immediately; all other severities use polite.
• [dismissed] uses display: none, removing the element from the accessibility tree entirely.

✅ Keyboard Navigation

• The close button is keyboard-reachable and has aria-label="Dismiss alert".
• [dismissing] disables pointer-events during the exit animation to prevent double-activation.

Dynamic insertion

Alerts injected into the DOM are announced automatically via role="alert". Avoid toggling color after insertion as it may trigger an unwanted re-announcement.

Best Practices

Do:

• Always supply a color to convey semantic intent (color="error" for failures, color="success" for confirmations, etc.).
• Use heading when you need to distinguish a short title from a longer explanation.
• Use accented to draw extra attention to a critical flat or bordered alert.
• Listen to dismiss and call e.target.remove() when you want the alert gone from the DOM, not just hidden.

Don't:

• Use bit-alert for short, transient notifications — use a toast/notification system instead.
• Combine horizontal with heading — the layout becomes cramped.
• Nest complex interactive controls in the default slot; keep alerts primarily informational.