Components

Dev Server

To run all packages/playgrounds/sites in watch mode, use the following command in the monorepo root:

pnpm dev

We’ve also provide a number of sub-commands for a more limited set of packages:

pnpm dev:{command}

• dev:docs - runs all dependencies for the Documentation website.
• dev:themes - runs all dependencies for the Theme Generator website.
• dev:svelte - runs all dependencies for the Svelte Playground.
• dev:react - runs all dependencies for the React Playground.

Server Ports

The following represents the default localhost address and port for each project. This will be displayed in the terminal when starting each dev server.

• Documentation Site: http://localhost:4321/
• Svelte Playground: http://localhost:5173/
• React Playground: http://localhost:3000/

You may run the sites and playgrounds in parallel at the same time. If a server shares a port, this will increment by one for the next server (ex: 5174, 5175, etc). Keep your eye on the terminal to retrieve the specific local address for each.

Zag.js

Skeleton components are built using a foundation of Zag.js. This provides a suite of headless component primitives that handle logic and state, while providing a universal set of features per all supported frameworks. The Skeleton design system is then implemented as a layer on top of this.

When introducing a new Skeleton component, please refer to the documentation for each respective framework. For example:

• Avatar (React): https://zagjs.com/components/react/avatar
• Avatar (Svelte): https://zagjs.com/components/svelte/avatar

Continue reading below to learn how implement the Zag primitives as components using Skeleton-specific conventions.

Adding Components

Anatomy

When creating a component, start by breaking it down into its core parts. If the component utilizes a Zag primitive, you may copy the source directly from Zag’s Usage section. For custom in-house components, you may use Skeleton’s common terminology and discuss the potential anatomy with Skeleton maintainers.

For example, the Zag Avatar component utilizes the following DOM structure:

<div>
  <img />
  <span>...</span>
</div>

As such, we’ll implement one component part respective of each element:

• <Avatar> - the root element
• <Avatar.Image> - the child image
• <Avatar.Fallback> - the fallback span

We’ll also include two special Skeleton-specific components:

• <Avatar.Provider> - Similar to <Avatar> but allows the user to pass in the api.
• <Avatar.Context> - Provides access to the component tree’s Context API.

Directory and File Names

Components are housed in the following location per framework:

Skeleton uses a consistent naming convention per component:

avatar/
├── anatomy/
│   ├── fallback.{tsx|svelte}
│   ├── image.{tsx|svelte}
│   ├── root-context.{tsx|svelte}
│   ├── root-provider.{tsx|svelte}
│   └── root.{tsx|svelte}
├── modules/
│   ├── anatomy.ts
│   ├── provider(.svelte).ts
│   └── root-context.ts
└── index.ts

Anatomy Folder

The anatomy folder contains each component part inside a seperate file.

Component Part File

Every component part should export their component as a default export and their prop types as named exports.

React

export interface AvatarRootProps {
  // ...
}

export default function Root(props: AvatarRootProps) {
  // ...
}

Svelte

<script lang="ts" module>
  export interface AvatarRootProps {
    // ...
  }
</script>

<script lang="ts">
  const props: AvatarRootProps = $props();

  // ...
</script>

<!-- ... --->

Note that you may need to extend or omit portions of the type to avoid conflicts between Zag and HTML attributes.

Extend

• PropsWithElement<Tag> - via Skeleton’s @/internal/props-with-element; allows for HTML template overrides.
• HTMLAttributes<Tag, Omit> - via Skeleton’s @/internal/html-attributes; allows for standard HTML attributes.

Omit

• Omit<Props, 'id'> - omit the id field from the Props interface as they will be provided inside the component itself.

Modules Folder

Anatomy File

The anatomy.ts file contains the exported anatomy, which enables the friendly dot notation syntax when consumed.

import Fallback from '../anatomy/fallback';
import Image from '../anatomy/image';
import Root from '../anatomy/root';

export const Avatar = Object.assign(
  Root, // <Avatar>
  {
    Image: Image, // <Avatar.Image>
    Fallback: Fallback, // <Avatar.Fallback>
  },
);

Context Files

The {part}-context.ts file contains the exported context for each component part’s context. This pattern enables strong typing of the context itself.

For most components this will only be necessary for the root component, some components however may require context for their children well. Reference existing components for real world examples.

import type { useAvatar } from './use-avatar';
import { createContext } from '@/internal/create-context';

export const AvatarRootContext = createContext<ReturnType<typeof useAvatar>>();

Index File

The index prepares all required component files for export.

export { Avatar } from './modules/anatomy';
export { useAvatar } from './modules/provider';
export type { AvatarRootProps } from './anatomy/root';
export type { AvatarRootProviderProps } from './anatomy/root-provider';
export type { AvatarRootContextProps } from './anatomy/root-context';
export type { AvatarImageProps } from './anatomy/image';
export type { AvatarFallbackProps } from './anatomy/fallback';

Component Exports

Finally, make sure to export the new component for each respective component’s framework package. This is handled in /packages/skeleton-{framework}/src/index.ts.

export * from './components/accordion/index';
export * from './components/avatar/index';
// ...

Using Zag Primitives

Source Code

Locate the respective framework component source code on the Zag website. For example:

In most cases, Zag provides all source code in a single file. Take care when splitting this into multiple component parts. We recommend starting with the root component - including the primitive imports, and defining the machine and api. Then utilize Context API and child components for each additional sub-component.

Context API

In some cases you may need to pass data from parent down to child components. For this, we can utilize each framework’s Context API:

Note that Skeleton implements a set convention for Context API to enable strong typing.

Common Conventions

While each component will present a unique set of challenges, we recommend you reference other existing components to see how we’ve handled specific situations. But there are a few common conventions we’ll detail below.

• Try to stick as close to the Zag implementation DOM structure and naming as possible; don’t get creative.
• Use whitespace to seperate Zag versus Skeleton logic, including: props, attributes, and context definitions.
• Avoid hardcoded english text or icons. Consider pass-throughs using props, snippets, or sub-components.
• Default to the named import pattern, such as import { foo, bar, fizz } from 'whatever'; (Including Zag’s imports)

React Specific

• Pass the id field into the useMachine hook using the useId() hook from react.
• Consume context using use(Context) from react.
• Use the className attribute to pass Skeleton classes.

Svelte Specific

• Pass the id field into the useMachine function using the props.id() rune from svelte.
• Consume context using the Context.consume().
• Use the class attribute to pass Skeleton classes.

NOTE: We welcome contributions to expand this section!

Styling Components

Component classes are now common and shared between all framework iterations. These reside in /packages/skeleton-common and are named to match their respective component.

packages/
└── skeleton-common/
  └── src/
    ├── classes/
    |  ├── accordion.ts
    |  ├── avatar.ts
    |  └── ...
    └── index.ts

Here’s an example of the Avatar styles found in avatar.ts:

import { defineSkeletonClasses } from '../internal/define-skeleton-classes' with { type: 'macro' };

export const classesAvatar = defineSkeletonClasses({
  root: 'isolate bg-surface-400-600 size-16 rounded-full overflow-hidden',
  image: 'w-full object-cover',
  fallback: 'size-full flex justify-center items-center',
});

• We’ll cover the import { type: 'macro' } in the style prefix section.
• Use the naming convention of classes{Component}
• Create a key for each component part.
• The values provide the default utility classes to the component’s class list.
• You can optionally pass an array of strings ['', ''] to document multi-line.
• Make sure to export the component class file in /packages/skeletlon-common/index.ts.

Array Notation

You can optionally provide an array of strings whenever the class list is long or can be split into logical sections. This improves readability. The defineSkeletonClasses function will flatten the array into a single string at build time.

import { defineSkeletonClasses } from '../internal/define-skeleton-classes' with { type: 'macro' };

export const classesProgress = defineSkeletonClasses({
  root: [
    // Common
    'items-center justify-center gap-2',
    // Horizontal Orientation
    'data-[orientation=horizontal]:flex data-[orientation=horizontal]:flex-row data-[orientation=horizontal]:w-full',
    // Vertical Orientation
    'data-[orientation=vertical]:inline-flex data-[orientation=vertical]:flex-col',
  ],
  // ...
});

Style Prefix

It’s worth noting that during build time, Skeleton will automatically prefix each class in the class list with skb: (short for “Skeleton Base”). By applying with { type: 'macro' } to the import, the import will run defineSkeletonClasses specifically at build time. This variant prefix will assign each class to the Tailwind @base layer, ensuring user-provided classes take precedence over our internally defined classes. This is accomplished using the following Tailwind custom variant.

@custom-variant skb {
  @layer base {
    @slot;
  }
}

If you need to prevent a class from being prefixed at build time, apply a variant of not-skb: to that class.

NOTE: This should be a rare use-case requiring discussion with the Skeleton team prior to implementation as it means the user won’t be able to override that specific class without using the anti-pattern: ! for !important.

Importing Class Lists

For Zag primitives, you can import and implement each class list Using Zag’s mergeProps utility for attributes.

import type { HTMLAttributes } from '@/internal/html-attributes';
import type { PropsWithElement } from '@/internal/props-with-element';
import { classesAvatar } from '@skeletonlabs/skeleton-common';
import type { Props } from '@zag-js/avatar';
import { mergeProps } from '@zag-js/react';

export interface AvatarRootProps extends Omit<Props, 'id'>, PropsWithElement<'div'>, HTMLAttributes<'div', 'id'> {
  // ...
}

export default function (props: AvatarRootProps) {
  const { children, ...rest } = props;

  const attributes = mergeProps(
    api.getRootProps(),
    {
      className: classesAvatar.root,
    },
    rest,
  );

  return <div {...attributes}>{children}</div>;
}

The process is similar for custom components without Zag primitives. We still use the Zag mergeProps utility, just without the api.getPartProps().

import { classesNavigation } from '@skeletonlabs/skeleton-common';
import { mergeProps } from '@zag-js/react';

export default function (props: NavigationRootProps) {
  const { children, ...rest } = props;

  const attributes = mergeProps(
    {
      className: classesNavigation.root,
    },
    rest,
  );

  return <div {...attributes}>{children}</div>;
}

Testing Components

We recommend you reference existing components to see how we’ve handled testing. Each framework has slightly different testing conventions, but all utilize Vitest with Testing Library.

Test files are located in packages/skeleton-{framework}/test/components/{component} and each contain two files:

• index.test.{tsx|tsx} - contains the actual test cases.
• test.{tsx/svelte} - contains a wrapper component used to provide data-testid attributes to each respective component part.

Additional Resources

• Component Party - easily compare features between each framework
• React Documentation - the React documentation website.
• Svelte Documentation - the Svelte documentation website.