// Check for off-by-one errors
for (let i = 0; i < array.length; i++) { }  // Correct
for (let i = 0; i <= array.length; i++) { } // Bug

// Check null handling
const value = obj?.property ?? defaultValue;

// SQL injection prevention
const query = 'SELECT * FROM users WHERE id = $1';
await db.query(query, [userId]); // Parameterized

// XSS prevention
const safe = DOMPurify.sanitize(userInput);

// Avoid N+1 queries
const users = await db.query(`
  SELECT u.*, array_agg(o.*) as orders
  FROM users u LEFT JOIN orders o ON u.id = o.user_id
  GROUP BY u.id
`);

{
  "score": 85,
  "issues": [
    {
      "severity": "warning",
      "file": "src/api.ts",
      "line": 42,
      "message": "Consider adding error handling"
    }
  ],
  "suggestions": ["Add unit tests", "Extract helper function"]
}