Code reviewHardcr-g189

Subject Hydration mismatchLevel Senior–Staff~24 minCommon in Storage & CDN interviewsIndustries Software development

Question

Review this React TypeScript component (Next.js App Router).

What a strong answer looks like

Separate real bugs from style. Rank issues by severity, point at the root cause rather than the symptom, and suggest a concrete fix — specific and kind.

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Code to reviewtsx

1function ThemeToggle() {2  const [theme, setTheme] = useState(3    typeof window !== 'undefined' ? localStorage.getItem('theme') ?? 'light' : 'light'4  );5 6  return (7    <button onClick={() => setTheme(theme === 'light' ? 'dark' : 'light')} className={theme}>8      Toggle theme9    </button>10  );11}

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