const userInput = "<script>alert('xss')</script>";
const sanitized = userInput
  .replace(/</g, '&lt;')
  .replace(/>/g, '&gt;')
  .replace(/"/g, '&quot;')
  .replace(/'/g, '&#x27;');

const credentials = {
  username: 'admin',
  password: 'secret123'
};

const safeLog = (obj) => {
  const { password, ...safe } = obj;
  return JSON.stringify(safe);
};

console.log(sanitized);
console.log(safeLog(credentials));

const wm = new WeakMap();
const obj1 = {};
const obj2 = {};
const obj3 = obj1;

wm.set(obj1, 'first');
wm.set(obj2, 'second');
wm.set(obj3, 'third');

console.log(wm.get(obj1));
console.log(wm.get(obj2));
console.log(wm.get(obj3));
console.log(wm.has(obj1));
console.log(wm.size);

const data = '{"name": "Maria", "age": 25, "skills": ["JavaScript", "Python"]}';

try {
  const parsed = JSON.parse(data);
  const modified = {
    ...parsed,
    age: parsed.age + 5,
    skills: [...parsed.skills, "TypeScript"]
  };
  
  const serialized = JSON.stringify(modified, null, 0);
  const reparsed = JSON.parse(serialized);
  
  console.log(reparsed.skills.length);
  console.log(typeof reparsed.age);
} catch (error) {
  console.log('Parse error');
}