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Atlas Whoff
Atlas Whoff

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Web Accessibility in React: Semantic HTML, ARIA, Focus Management, and axe Testing

#a11y #react #css #webdev

Accessibility isn't a feature you add at the end — it's a quality signal that correlates with better code overall. Well-structured, accessible apps tend to have better semantics, better keyboard behavior, and better performance. Here's the practical implementation.

Semantic HTML First

Every accessibility problem that seems hard is often just a semantic HTML problem:

// Bad -- div soup, no semantics
<div className='header'>
  <div className='nav'>
    <div onClick={handleClick}>Home</div>
    <div onClick={handleClick}>About</div>
  </div>
</div>

// Good -- semantic HTML, keyboard accessible automatically
<header>
  <nav aria-label='Main navigation'>
    <ul>
      <li><a href='/'>Home</a></li>
      <li><a href='/about'>About</a></li>
    </ul>
  </nav>
</header>
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Landmark elements (<header>, <nav>, <main>, <aside>, <footer>) give screen reader users a way to jump between sections.

ARIA: When and When Not To

ARIA attributes add semantic meaning when HTML alone isn't enough. But they don't add behavior — you must implement keyboard interaction yourself:

// Custom dropdown -- requires ARIA + keyboard handling
function Dropdown({ label, options, value, onChange }) {
  const [isOpen, setIsOpen] = useState(false)
  const listboxId = useId()

  return (
    <div>
      <button
        aria-haspopup='listbox'
        aria-expanded={isOpen}
        aria-controls={listboxId}
        onClick={() => setIsOpen(!isOpen)}
        onKeyDown={(e) => {
          if (e.key === 'Escape') setIsOpen(false)
          if (e.key === 'ArrowDown') { setIsOpen(true); /* focus first option */ }
        }}
      >
        {value || label}
      </button>
      {isOpen && (
        <ul id={listboxId} role='listbox' aria-label={label}>
          {options.map(opt => (
            <li
              key={opt.value}
              role='option'
              aria-selected={value === opt.value}
              onClick={() => { onChange(opt.value); setIsOpen(false) }}
              tabIndex={0}
            >
              {opt.label}
            </li>
          ))}
        </ul>
      )}
    </div>
  )
}
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The rule: if a native HTML element does what you need (<select>, <button>, <a>), use it. ARIA is for custom widgets.

Focus Management 

// Dialog -- trap focus inside when open
import { useEffect, useRef } from 'react'

function Dialog({ isOpen, onClose, children }) {
  const dialogRef = useRef<HTMLDivElement>(null)

  useEffect(() => {
    if (!isOpen) return

    // Focus the dialog on open
    dialogRef.current?.focus()

    // Trap focus
    const focusable = dialogRef.current?.querySelectorAll(
      'button, [href], input, select, textarea, [tabindex]:not([tabindex="-1"])'
    )
    const first = focusable?.[0] as HTMLElement
    const last = focusable?.[focusable.length - 1] as HTMLElement

    const trap = (e: KeyboardEvent) => {
      if (e.key !== 'Tab') return
      if (e.shiftKey ? document.activeElement === first : document.activeElement === last) {
        e.preventDefault()
        ;(e.shiftKey ? last : first)?.focus()
      }
    }

    document.addEventListener('keydown', trap)
    return () => document.removeEventListener('keydown', trap)
  }, [isOpen])

  return (
    <div
      ref={dialogRef}
      role='dialog'
      aria-modal='true'
      tabIndex={-1}
      onKeyDown={(e) => e.key === 'Escape' && onClose()}
    >
      {children}
    </div>
  )
}
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Color Contrast and Visual Design

WCAG AA requires 4.5:1 contrast for normal text, 3:1 for large text:

// Check contrast in your Tailwind config
// Gray-500 on white: 3.95:1 -- FAILS AA for normal text
// Gray-700 on white: 8.59:1 -- passes AAA

// Don't rely on color alone to convey information
// Bad: red = error (invisible to colorblind users)
// Good: red + icon + error message text
<div className='flex items-center gap-2 text-red-600'>
  <AlertCircle className='w-4 h-4' aria-hidden='true' />
  <span role='alert'>Email is invalid</span>
</div>
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Automated Testing with axe 

npm install -D @axe-core/react jest-axe
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import { axe, toHaveNoViolations } from 'jest-axe'
expect.extend(toHaveNoViolations)

it('has no accessibility violations', async () => {
  const { container } = render(<LoginForm />)
  const results = await axe(container)
  expect(results).toHaveNoViolations()
})
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