Best Practices

Follow these best practices to build accessible, performant, and maintainable applications with Nim UI.

Component Usage

Import Only What You Need

Tree-shakeable imports reduce bundle size:

// ✅ Good - imports only Button
import { Button } from '@nim-ui/components';

// ❌ Bad - imports entire library
import * as NimUI from '@nim-ui/components';

Use Semantic HTML

Leverage semantic HTML elements for better accessibility:

// ✅ Good - semantic structure
<nav>
  <Button variant="ghost">Home</Button>
  <Button variant="ghost">About</Button>
</nav>

// ❌ Bad - divs for everything
<div>
  <div onClick={goHome}>Home</div>
  <div onClick={goAbout}>About</div>
</div>

Prefer Composition

Build complex UIs by composing simple components:

// ✅ Good - composable
<Card>
  <Card.Header>
    <h2>Title</h2>
  </Card.Header>
  <Card.Body>
    <p>Content</p>
  </Card.Body>
  <Card.Footer>
    <Button>Action</Button>
  </Card.Footer>
</Card>

// ❌ Bad - monolithic props
<Card
  title="Title"
  content="Content"
  actionLabel="Action"
  onAction={handleAction}
/>

Accessibility

Always Provide Labels

Every interactive element needs a label:

// ✅ Good - has accessible label
<Button aria-label="Close dialog">
  <XIcon />
</Button>

// ❌ Bad - no label for icon-only button
<Button>
  <XIcon />
</Button>

Maintain Focus Management

Handle focus properly in modals and dynamic content:

import { useEffect, useRef } from 'react';

function Modal({ isOpen, onClose }) {
  const closeButtonRef = useRef<HTMLButtonElement>(null);

  useEffect(() => {
    if (isOpen) {
      // Focus the close button when modal opens
      closeButtonRef.current?.focus();
    }
  }, [isOpen]);

  return (
    <div role="dialog" aria-modal="true">
      <Button ref={closeButtonRef} onClick={onClose}>
        Close
      </Button>
    </div>
  );
}

Ensure all interactions work via keyboard:

function SearchBox() {
  const handleKeyDown = (e: React.KeyboardEvent) => {
    if (e.key === 'Enter') {
      handleSearch();
    }
    if (e.key === 'Escape') {
      clearSearch();
    }
  };

  return (
    <Input
      onKeyDown={handleKeyDown}
      placeholder="Search..."
    />
  );
}

Color Contrast

Ensure sufficient color contrast (WCAG AA: 4.5:1):

// ✅ Good - high contrast
<div className="bg-neutral-900 text-white">
  High contrast text
</div>

// ❌ Bad - low contrast
<div className="bg-neutral-300 text-neutral-400">
  Hard to read
</div>

Performance

Lazy Load Heavy Components

Use React.lazy for code splitting:

import { lazy, Suspense } from 'react';
import { Spinner } from '@nim-ui/components';

const HeavyChart = lazy(() => import('./HeavyChart'));

function Dashboard() {
  return (
    <Suspense fallback={<Spinner />}>
      <HeavyChart />
    </Suspense>
  );
}

Memoize Expensive Computations

Use useMemo for expensive calculations:

import { useMemo } from 'react';

function DataTable({ data }) {
  const sortedData = useMemo(() => {
    return data.sort((a, b) => a.name.localeCompare(b.name));
  }, [data]);

  return <Table data={sortedData} />;
}

Debounce User Input

Debounce search and autocomplete inputs:

import { useState, useEffect } from 'react';

function SearchInput() {
  const [query, setQuery] = useState('');
  const [debouncedQuery, setDebouncedQuery] = useState('');

  useEffect(() => {
    const timer = setTimeout(() => {
      setDebouncedQuery(query);
    }, 300);

    return () => clearTimeout(timer);
  }, [query]);

  useEffect(() => {
    if (debouncedQuery) {
      performSearch(debouncedQuery);
    }
  }, [debouncedQuery]);

  return (
    <Input
      value={query}
      onChange={(e) => setQuery(e.target.value)}
      placeholder="Search..."
    />
  );
}

Virtualize Long Lists

Use virtualization for long lists:

import { useVirtualizer } from '@tanstack/react-virtual';

function VirtualList({ items }) {
  const parentRef = useRef<HTMLDivElement>(null);

  const virtualizer = useVirtualizer({
    count: items.length,
    getScrollElement: () => parentRef.current,
    estimateSize: () => 50,
  });

  return (
    <div ref={parentRef} style={{ height: '400px', overflow: 'auto' }}>
      {virtualizer.getVirtualItems().map((virtualItem) => (
        <div key={virtualItem.key}>
          {items[virtualItem.index]}
        </div>
      ))}
    </div>
  );
}

Form Handling

Validate on Submit

Validate forms on submit rather than on every keystroke:

function ContactForm() {
  const [errors, setErrors] = useState({});

  const handleSubmit = (e: React.FormEvent) => {
    e.preventDefault();

    const formData = new FormData(e.currentTarget);
    const validationErrors = validate(formData);

    if (Object.keys(validationErrors).length > 0) {
      setErrors(validationErrors);
      return;
    }

    submitForm(formData);
  };

  return (
    <form onSubmit={handleSubmit}>
      <Input name="email" />
      {errors.email && <span>{errors.email}</span>}
      <Button type="submit">Submit</Button>
    </form>
  );
}

Use Controlled Components Wisely

Only use controlled components when necessary:

// ✅ Good - uncontrolled for simple forms
<form onSubmit={handleSubmit}>
  <Input name="email" defaultValue="" />
</form>

// ✅ Good - controlled when you need the value
function SearchForm() {
  const [query, setQuery] = useState('');

  return (
    <Input
      value={query}
      onChange={(e) => setQuery(e.target.value)}
    />
  );
}

Show Clear Error Messages

Provide specific, actionable error messages:

// ✅ Good - specific and helpful
{error && (
  <p className="text-red-600">Email must be in format: user@example.com</p>
)}

// ❌ Bad - vague
{error && <p>Invalid input</p>}

State Management

Keep State Close to Where It's Used

Don't lift state unnecessarily:

// ✅ Good - state in component that uses it
function ToggleButton() {
  const [isOn, setIsOn] = useState(false);

  return (
    <Button onClick={() => setIsOn(!isOn)}>
      {isOn ? 'On' : 'Off'}
    </Button>
  );
}

// ❌ Bad - unnecessarily lifted state
function Parent() {
  const [isOn, setIsOn] = useState(false);

  return <Child isOn={isOn} setIsOn={setIsOn} />;
}

Use Context for Global State

Use Context API for truly global state:

import { createContext, useContext } from 'react';

const ThemeContext = createContext();

export function ThemeProvider({ children }) {
  const [theme, setTheme] = useState('light');

  return (
    <ThemeContext.Provider value={{ theme, setTheme }}>
      {children}
    </ThemeContext.Provider>
  );
}

export function useTheme() {
  return useContext(ThemeContext);
}

Styling

Extend, Don't Override

Extend component styles with className:

// ✅ Good - extends base styles
<Button className="rounded-full shadow-lg">
  Custom
</Button>

// ❌ Bad - inline styles that override
<Button style={{ borderRadius: '9999px' }}>
  Custom
</Button>

Use Tailwind Utilities

Prefer Tailwind utilities over custom CSS:

// ✅ Good - Tailwind utilities
<div className="flex items-center justify-between gap-4">
  Content
</div>

// ❌ Bad - custom CSS
<div style={{
  display: 'flex',
  alignItems: 'center',
  justifyContent: 'space-between',
  gap: '1rem'
}}>
  Content
</div>

Follow the Design System

Use design tokens consistently:

// ✅ Good - uses design tokens
<div className="text-neutral-900 dark:text-neutral-100">
  Text
</div>

// ❌ Bad - arbitrary colors
<div className="text-[#1a1a1a]">
  Text
</div>

TypeScript

Define Proper Types

Use TypeScript for type safety:

// ✅ Good - proper types
interface User {
  id: string;
  name: string;
  email: string;
}

function UserCard({ user }: { user: User }) {
  return <Card>{user.name}</Card>;
}

// ❌ Bad - any types
function UserCard({ user }: { user: any }) {
  return <Card>{user.name}</Card>;
}

Use Type Inference

Let TypeScript infer types when possible:

// ✅ Good - inferred types
const [count, setCount] = useState(0);
const users = data.map(user => user.name);

// ❌ Bad - unnecessary explicit types
const [count, setCount] = useState<number>(0);
const users: string[] = data.map((user: User) => user.name);

Testing

Test User Interactions

Focus on testing user behavior:

import { render, screen, fireEvent } from '@testing-library/react';

test('button calls onClick when clicked', () => {
  const handleClick = vi.fn();

  render(<Button onClick={handleClick}>Click me</Button>);

  fireEvent.click(screen.getByText('Click me'));

  expect(handleClick).toHaveBeenCalledOnce();
});

Use Semantic Queries

Query by accessible roles and labels:

// ✅ Good - semantic query
const button = screen.getByRole('button', { name: 'Submit' });

// ❌ Bad - implementation detail
const button = screen.getByClassName('btn-primary');

Security

Sanitize User Input

Never render unsanitized user content:

import DOMPurify from 'dompurify';

function UserContent({ content }) {
  const sanitized = DOMPurify.sanitize(content);

  return <div dangerouslySetInnerHTML={{ __html: sanitized }} />;
}

Validate on Server

Always validate on the server, not just client:

// Client-side validation for UX
function SignupForm() {
  const handleSubmit = async (data) => {
    // Client validation
    if (!data.email) {
      setError('Email required');
      return;
    }

    // Server validates again
    const response = await fetch('/api/signup', {
      method: 'POST',
      body: JSON.stringify(data),
    });
  };
}

Documentation

Comment Complex Logic

Add comments for non-obvious code:

function calculateDiscount(price: number, tier: string) {
  // Corporate tier gets 30% bulk discount
  // Enterprise tier gets 50% volume discount
  const multiplier = tier === 'enterprise' ? 0.5 : 0.7;

  return price * multiplier;
}

Use JSDoc for Public APIs

Document public functions and components:

/**
 * Formats a price with currency symbol
 *
 * @param amount - The numeric amount
 * @param currency - Currency code (USD, EUR, etc.)
 * @returns Formatted price string
 *
 * @example
 * formatPrice(1999, 'USD') // "$19.99"
 */
function formatPrice(amount: number, currency: string): string {
  return new Intl.NumberFormat('en-US', {
    style: 'currency',
    currency,
  }).format(amount / 100);
}

Checklist

Before deploying to production:

Best Practices

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