component-design

Component design

Stack-agnostic principles, concrete examples in React 19 and React Native. The examples port to Vue/Svelte; the judgments don't change.

Version targets: React 19, React Native 0.81 (current stable). Snippets grounded against Context7 (/reactjs/react.dev, /facebook/react-native) at authoring time — see references/snippets.md.

The core question

Every component decision reduces to: what does this component own, and what does it merely render? Owned state and behavior justify a component; pure rendering of parent-owned data is often a prop or a child, not a new component.

Principles

• Compose over configure. Prefer children and slot props to a growing list of boolean flags. A component with eight is*/show* props is usually several components wearing a trench coat.
• Lift state to its lowest common owner — no higher. State lives at the closest ancestor that needs it. Lifting "just in case" creates prop-drilling and re-render cost.
• Keep the public prop surface narrow and honest. Props are an API. Fewer, well-named props beat many overlapping ones. Don't leak implementation (no className/style pass-through unless the component is genuinely a primitive).
• Decide controlled vs uncontrolled deliberately. Uncontrolled (owns its state) is easier to drop in; controlled (driven by props) is coordinable. Pick per piece of information, and say which in the prop names.
• Separate layout from data. A component that both fetches and lays out is hard to reuse and test. Split the data owner from the presentational shell.
• Mobile parity. The same ownership rules hold in React Native; the difference is primitives (View/Text/Pressable) and that list item components render many times, so they must be cheap. See references/pitfalls.md.
• Show visual choices, don't describe them. When a decision is genuinely visual — which composition or layout — render the options for the user with the brainstorming visual companion (superpowers:brainstorming) and let them click, instead of asking in prose. "Which of these feels right?" is for the companion; "what should this do?" stays in the terminal.

How to use this skill

1. Run references/checklist.md against the component you're designing or reviewing.
2. Reach for a pattern in references/snippets.md (composition, compound components, controlled/uncontrolled, RN list item).
3. Check references/pitfalls.md before you ship — most component PRs hit at least one.

Related

• State that crosses components → state-management
• Styling the component → styling-systems
• Making it accessible → accessibility-audit
• Testing it by behavior → frontend-testing
• Comparing visual options with the user → superpowers:brainstorming (visual companion)