code-showcase-react-ui-patterns

1

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Summary

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SKILL.md

React UI Patterns

When to Use

Use this skill when you need modern React UI patterns for loading states, error handling, and data fetching. Use when building UI components, handling async data, or managing UI states.

Core Principles

Never show stale UI - Loading spinners only when actually loading
Always surface errors - Users must know when something fails
Optimistic updates - Make the UI feel instant
Progressive disclosure - Show content as it becomes available
Graceful degradation - Partial data is better than no data

Loading State Patterns

The Golden Rule

Show loading indicator ONLY when there's no data to display.

// CORRECT - Only show loading when no data exists
const { data, loading, error } = useGetItemsQuery();

if (error) return <ErrorState error={error} onRetry={refetch} />;
if (loading && !data) return <LoadingState />;
if (!data?.items.length) return <EmptyState />;

return <ItemList items={data.items} />;

// WRONG - Shows spinner even when we have cached data
if (loading) return <LoadingState />; // Flashes on refetch!

Loading State Decision Tree

Is there an error?
  → Yes: Show error state with retry option
  → No: Continue

Is it loading AND we have no data?
  → Yes: Show loading indicator (spinner/skeleton)
  → No: Continue

Do we have data?
  → Yes, with items: Show the data
  → Yes, but empty: Show empty state
  → No: Show loading (fallback)

Skeleton vs Spinner

Use Skeleton When	Use Spinner When
Known content shape	Unknown content shape
List/card layouts	Modal actions
Initial page load	Button submissions
Content placeholders	Inline operations

Error Handling Patterns

1. Inline error (field-level) → Form validation errors
2. Toast notification → Recoverable errors, user can retry
3. Error banner → Page-level errors, data still partially usable
4. Full error screen → Unrecoverable, needs user action

// CORRECT - Error always surfaced to user
const [createItem, { loading }] = useCreateItemMutation({
  onCompleted: () => {
    toast.success({ title: 'Item created' });
  },
  onError: (error) => {
    console.error('createItem failed:', error);
    toast.error({ title: 'Failed to create item' });
  },
});

// WRONG - Error silently caught, user has no idea
const [createItem] = useCreateItemMutation({
  onError: (error) => {
    console.error(error); // User sees nothing!
  },
});

interface ErrorStateProps {
  error: Error;
  onRetry?: () => void;
  title?: string;
}

const ErrorState = ({ error, onRetry, title }: ErrorStateProps) => (
  <div className="error-state">
    <Icon name="exclamation-circle" />
    <h3>{title ?? 'Something went wrong'}</h3>
    <p>{error.message}</p>
    {onRetry && (
      <Button onClick={onRetry}>Try Again</Button>
    )}
  </div>
);

<Button
  onClick={handleSubmit}
  isLoading={isSubmitting}
  disabled={!isValid || isSubmitting}
>
  Submit
</Button>

// CORRECT - Button disabled while loading
<Button
  disabled={isSubmitting}
  isLoading={isSubmitting}
  onClick={handleSubmit}
>
  Submit
</Button>

// WRONG - User can tap multiple times
<Button onClick={handleSubmit}>
  {isSubmitting ? 'Submitting...' : 'Submit'}
</Button>

// WRONG - No empty state
return <FlatList data={items} />;

// CORRECT - Explicit empty state
return (
  <FlatList
    data={items}
    ListEmptyComponent={<EmptyState />}
  />
);

// Search with no results
<EmptyState
  icon="search"
  title="No results found"
  description="Try different search terms"
/>

// List with no items yet
<EmptyState
  icon="plus-circle"
  title="No items yet"
  description="Create your first item"
  action={{ label: 'Create Item', onClick: handleCreate }}
/>

const MyForm = () => {
  const [submit, { loading }] = useSubmitMutation({
    onCompleted: handleSuccess,
    onError: handleError,
  });

  const handleSubmit = async () => {
    if (!isValid) {
      toast.error({ title: 'Please fix errors' });
      return;
    }
    await submit({ variables: { input: values } });
  };

  return (
    <form>
      <Input
        value={values.name}
        onChange={handleChange('name')}
        error={touched.name ? errors.name : undefined}
      />
      <Button
        type="submit"
        onClick={handleSubmit}
        disabled={!isValid || loading}
        isLoading={loading}
      >
        Submit
      </Button>
    </form>
  );
};

// WRONG - Spinner when data exists (causes flash)
if (loading) return <Spinner />;

// CORRECT - Only show loading without data
if (loading && !data) return <Spinner />;

// WRONG - Error swallowed
try {
  await mutation();
} catch (e) {
  console.log(e); // User has no idea!
}

// CORRECT - Error surfaced
onError: (error) => {
  console.error('operation failed:', error);
  toast.error({ title: 'Operation failed' });
}

// WRONG - Button not disabled during submission
<Button onClick={submit}>Submit</Button>

// CORRECT - Disabled and shows loading
<Button onClick={submit} disabled={loading} isLoading={loading}>
  Submit
</Button>