const user = {
  name: 'Alice',
  age: 30
};

const handler = {
  get(target, prop) {
    if (prop in target) {
      return target[prop];
    }
    return `Property '${prop}' doesn't exist`;
  },
  set(target, prop, value) {
    if (prop === 'age' && typeof value !== 'number') {
      console.log('Age must be a number');
      return false;
    }
    target[prop] = value;
    return true;
  }
};

const proxy = new Proxy(user, handler);
proxy.age = '32';
proxy.age = 32;
console.log(proxy.job);