focus-management（焦点管理）

Focus Management

Essential patterns for managing keyboard focus in accessible web applications, ensuring keyboard-only users can navigate complex interactive components.

Overview

• Building modals, dialogs, or drawers that require focus trapping
• Implementing tab panels, menus, or toolbars with roving tabindex
• Restoring focus after closing overlays or completing actions
• Creating skip links for keyboard navigation
• Ensuring focus visibility meets WCAG 2.4.7 requirements

Quick Reference

FocusScope Trap (React Aria)

import { FocusTrap } from '@react-aria/focus';

function Modal({ isOpen, onClose, children }) {
  if (!isOpen) return null;
  return (
    <div role="dialog" aria-modal="true">
      <FocusTrap>
        <div className="modal-content">
          {children}
          <button onClick={onClose}>Close</button>
        </div>
      </FocusTrap>
    </div>
  );
}

Roving Tabindex

function TabList({ tabs, onSelect }) {
  const [activeIndex, setActiveIndex] = useState(0);
  const tabRefs = useRef<HTMLButtonElement[]>([]);

  const handleKeyDown = (e: KeyboardEvent, index: number) => {
    const keyMap: Record<string, number> = {
      ArrowRight: (index + 1) % tabs.length,
      ArrowLeft: (index - 1 + tabs.length) % tabs.length,
      Home: 0, End: tabs.length - 1,
    };
    if (e.key in keyMap) {
      e.preventDefault();
      setActiveIndex(keyMap[e.key]);
      tabRefs.current[keyMap[e.key]]?.focus();
    }
  };

  return (
    <div role="tablist">
      {tabs.map((tab, i) => (
        <button key={tab.id} ref={(el) => (tabRefs.current[i] = el!)}
          role="tab" tabIndex={i === activeIndex ? 0 : -1}
          aria-selected={i === activeIndex}
          onKeyDown={(e) => handleKeyDown(e, i)}
          onClick={() => { setActiveIndex(i); onSelect(tab); }}>
          {tab.label}
        </button>
      ))}
    </div>
  );
}

Focus Restore

function useRestoreFocus(isOpen: boolean) {
  const triggerRef = useRef<HTMLElement | null>(null);

  useEffect(() => {
    if (isOpen) {
      triggerRef.current = document.activeElement as HTMLElement;
    } else if (triggerRef.current) {
      triggerRef.current.focus();
      triggerRef.current = null;
    }
  }, [isOpen]);
}

Key Decisions

Anti-Patterns (FORBIDDEN)

// NEVER use positive tabindex - breaks natural tab order
<button tabIndex={5}>Bad</button>

// NEVER remove focus outline without replacement (WCAG 2.4.7)
button:focus { outline: none; }

// NEVER trap focus without Escape key handler
<FocusTrap><div>No way out!</div></FocusTrap>

// NEVER auto-focus without user expectation
useEffect(() => inputRef.current?.focus(), []);

// NEVER hide skip links permanently - must be visible on focus
.skip-link { display: none; }

Related Skills

• a11y-testing - Test focus management with Playwright and axe
• design-system-starter - Focus indicators in design tokens
• motion-animation-patterns - Animate focus transitions accessibly

Capability Details

focus-trap

Keywords: focus trap, modal focus, dialog focus, FocusTrap, aria-modal Solves:

• Trap focus within modals and dialogs
• Prevent focus escaping to background content
• Handle Escape key to close and release trap

roving-tabindex

Keywords: roving tabindex, arrow navigation, tablist, menu keyboard Solves:

• Navigate widget items with arrow keys
• Maintain single tab stop for composite widgets
• Support Home/End for quick navigation

focus-restore

Keywords: focus restore, return focus, trigger focus, focus memory Solves:

• Return focus to trigger after closing overlay
• Preserve focus context across interactions
• Handle focus when elements are removed from DOM