Slot-Based Customization

Slot-based customization enables component flexibility through designated content areas where consumers inject their own elements. Slots provide controlled extension points that maintain component structure while allowing content variation. This pattern reduces drift by offering sanctioned customization paths.

What Is Slot-Based Customization

Slots are designated areas within components where consumers can provide custom content. A card component might have slots for header, body, actions, and footer. Consumers customize by providing content for relevant slots rather than modifying the card component itself.

Slots separate component structure from component content. The design system controls how slots are arranged, styled, and behave. Consumers control what content appears in slots. This separation enables customization without structural modification.

How Slot-Based Customization Works

Named slots identify distinct customization areas. Components define slots with semantic names like header, content, footer, leading, trailing. Named slots enable precise content placement. Consumers provide content by slot name.

Default slot content provides fallback behavior. Slots can specify content that appears when consumers do not provide alternatives. Defaults enable components to work without explicit slot content while allowing customization when needed.

Slot validation constrains what content is appropriate. Slots might accept only certain component types or enforce content requirements. Validation prevents inappropriate content that would break component functionality or appearance.

Slot rendering integration incorporates consumer content into component output. Component implementations render slot content in appropriate locations with appropriate context. Rendering might wrap content, provide props, or apply styles.

Framework implementation varies by technology. React uses children and render props. Vue has named slots as a native feature. Web Components use the slot element. Angular uses ng-content with select attributes. Implementation details differ but the conceptual pattern remains consistent.

Key Considerations

• Slot design should reflect common customization needs
• Too many slots create complexity; too few limit flexibility
• Slot naming should be intuitive and consistent across components
• Slot documentation should show usage examples
• Slot styling integration affects visual consistency

Common Questions

How should slot content interact with component styling?

Slot content styling requires careful consideration. Components typically apply structural styling to slot areas: positioning, spacing, and dimensional constraints. Content styling may be left to consumers or may apply component-consistent defaults. Typography and color tokens might be inherited into slot areas for consistency. Consumers should be able to override defaults when needed. Clear documentation should explain what styling slots inherit and what consumers control. Slot styling boundaries help consumers understand how to style their content appropriately.

When should components use slots versus props?

Slots suit complex, variable content that cannot be reduced to simple values. Props suit simple values, flags, and configurations. A title prop makes sense for single-line text. A header slot makes sense for complex header content including icons, actions, and multi-line text. Props suit enumerable options; slots suit unbounded possibilities. The distinction is not absolute; some needs could be addressed either way. Consider what consumers will commonly provide: if it is usually simple values, props may be cleaner; if it requires flexibility, slots may serve better.

Summary

Slot-based customization enables flexibility through named content areas that separate component structure from content, with default content for fallback behavior, validation constraining appropriate content, and framework-specific implementation handling rendering. Slot content styling requires clarity about what slots inherit and what consumers control. Slots suit complex variable content while props suit simple values and configurations.