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CSS Modules

Learn how to use CSS Modules in Bini.js for component-scoped styling.

CSS Modules allow you to write component-scoped CSS without worrying about naming conflicts. Vite processes .module.css files automatically — no configuration needed.

Zero Configuration: Vite handles CSS Modules natively. Any file ending in .module.css is automatically processed as a CSS Module.

Basic Usage

Create a .module.css file and import it in your component:

Button.module.css
/* src/app/components/Button.module.css */
.button {
  padding: 0.5rem 1rem;
  border-radius: 0.5rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s;
}

.primary {
  background: #06b6d4;
  color: black;
  border: none;
}

.primary:hover {
  background: #0891b2;
}
Button.tsx
// src/app/components/Button.tsx
import styles from './Button.module.css'

export function Button({ variant = 'primary', children }) {
  return (
    <button className={`${styles.button} ${styles[variant]}`}>
      {children}
    </button>
  )
}

Combining Classes

Combine multiple CSS Module classes using template literals:

Card.module.css
/* src/app/components/Card.module.css */
.card {
  background: #0a0a0a;
  border: 1px solid #1e293b;
  border-radius: 0.75rem;
  padding: 1.5rem;
}

.featured {
  border-color: #06b6d4;
}

.large {
  padding: 2rem;
}
Card.tsx
// src/app/components/Card.tsx
import styles from './Card.module.css'

export function Card({ featured, size = 'normal', children }) {
  return (
    <div className={`${styles.card} ${featured ? styles.featured : ''} ${size === 'large' ? styles.large : ''}`}>
      {children}
    </div>
  )
}
Use the clsx or classnames library for cleaner conditional class composition.

Using clsx for Cleaner Code

Install clsx for cleaner conditional classes:

npm install clsx
Card.tsx
// src/app/components/Card.tsx
import clsx from 'clsx'
import styles from './Card.module.css'

export function Card({ featured, size = 'normal', children }) {
  return (
    <div className={clsx(
      styles.card,
      featured && styles.featured,
      size === 'large' && styles.large
    )}>
      {children}
    </div>
  )
}

Global vs Local Scope

CSS Modules are locally scoped by default. Use :global to target global selectors:

Container.module.css
/* src/app/components/Container.module.css */
.container {
  max-width: 1200px;
  margin: 0 auto;
}

.container :global(.heading) {
  margin-bottom: 1rem;
}

:global(.dark) .container {
  background: #000;
}

Composing Classes

Use composes to reuse styles from other classes:

Form.module.css
/* src/app/components/Form.module.css */
.baseInput {
  width: 100%;
  padding: 0.5rem 0.75rem;
  border-radius: 0.5rem;
  border: 1px solid #334155;
  background: #0a0a0a;
  color: white;
}

.textInput {
  composes: baseInput;
}

.errorInput {
  composes: baseInput;
  border-color: #ef4444;
}

CSS Variables in Modules

Use CSS variables for dynamic styling within modules:

Progress.module.css
/* src/app/components/Progress.module.css */
.bar {
  height: 100%;
  width: var(--progress);
  background: linear-gradient(to right, #06b6d4, #3b82f6);
  transition: width 0.3s ease;
}
Progress.tsx
// src/app/components/Progress.tsx
import styles from './Progress.module.css'

export function Progress({ value, max = 100 }) {
  const percentage = (value / max) * 100
  
  return (
    <div className={styles.progress}>
      <div 
        className={styles.bar} 
        style={{ '--progress': `${percentage}%` } as React.CSSProperties}
      />
    </div>
  )
}

Animations

Define animations in CSS Modules:

Spinner.module.css
/* src/app/components/Spinner.module.css */
.spinner {
  width: 2rem;
  height: 2rem;
  border: 3px solid #1e293b;
  border-top-color: #06b6d4;
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

@keyframes spin {
  to {
    transform: rotate(360deg);
  }
}
Spinner.tsx
// src/app/components/Spinner.tsx
import styles from './Spinner.module.css'

export function Spinner() {
  return <div className={styles.spinner} />
}

Media Queries

Write responsive styles with media queries:

Grid.module.css
/* src/app/components/Grid.module.css */
.grid {
  display: grid;
  gap: 1rem;
  grid-template-columns: 1fr;
}

@media (min-width: 640px) {
  .grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (min-width: 1024px) {
  .grid {
    grid-template-columns: repeat(3, 1fr);
  }
}

Complete Example

A full-featured modal component using CSS Modules:

Modal.module.css
/* src/app/components/Modal.module.css */
.overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.8);
  backdrop-filter: blur(4px);
  display: flex;
  align-items: center;
  justify-content: center;
}

.modal {
  background: #0a0a0a;
  border: 1px solid #1e293b;
  border-radius: 1rem;
  padding: 1.5rem;
  max-width: 500px;
  width: 90%;
}

.title {
  font-size: 1.25rem;
  font-weight: 600;
  color: white;
}

.close {
  background: transparent;
  color: #94a3b8;
  border: none;
  cursor: pointer;
}

.close:hover {
  color: white;
}
Modal.tsx
// src/app/components/Modal.tsx
import styles from './Modal.module.css'

export function Modal({ isOpen, onClose, title, children }) {
  if (!isOpen) return null

  return (
    <div className={styles.overlay} onClick={onClose}>
      <div className={styles.modal} onClick={e => e.stopPropagation()}>
        <div className="flex items-center justify-between mb-4">
          <h2 className={styles.title}>{title}</h2>
          <button className={styles.close} onClick={onClose}>✕</button>
        </div>
        <div className="text-slate-400">{children}</div>
      </div>
    </div>
  )
}
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