ECC/rules/web/patterns.md

paths

paths
**/*.css **/*.scss **/*.sass **/*.less **/*.html **/*.tsx **/*.jsx **/*.vue **/*.svelte

This file extends common/patterns.md with web-specific patterns.

Web Patterns

Component Composition

Compound Components

Use compound components when related UI shares state and interaction semantics:

<Tabs defaultValue="overview">
  <Tabs.List>
    <Tabs.Trigger value="overview">Overview</Tabs.Trigger>
    <Tabs.Trigger value="settings">Settings</Tabs.Trigger>
  </Tabs.List>
  <Tabs.Content value="overview">...</Tabs.Content>
  <Tabs.Content value="settings">...</Tabs.Content>
</Tabs>

• Parent owns state
• Children consume via context
• Prefer this over prop drilling for complex widgets

Render Props / Slots

• Use render props or slot patterns when behavior is shared but markup must vary
• Keep keyboard handling, ARIA, and focus logic in the headless layer

Container / Presentational Split

• Container components own data loading and side effects
• Presentational components receive props and render UI
• Presentational components should stay pure

State Management

Treat these separately:

Concern	Tooling
Server state	TanStack Query, SWR, tRPC
Client state	Zustand, Jotai, signals
URL state	search params, route segments
Form state	React Hook Form or equivalent

• Do not duplicate server state into client stores
• Derive values instead of storing redundant computed state

URL As State

Persist shareable state in the URL:

• filters
• sort order
• pagination
• active tab
• search query

Data Fetching

Stale-While-Revalidate

• Return cached data immediately
• Revalidate in the background
• Prefer existing libraries instead of rolling this by hand

Optimistic Updates

• Snapshot current state
• Apply optimistic update
• Roll back on failure
• Emit visible error feedback when rolling back

Parallel Loading

• Fetch independent data in parallel
• Avoid parent-child request waterfalls
• Prefetch likely next routes or states when justified