如何在javascript中使用递归查找对象？

function findProperty(obj, propName) {
  if (obj === null || typeof obj === 'undefined') {
    return null;
  }
  
  if (obj.hasOwnProperty(propName)) {
    return obj[propName];
  }
  
  for (let key in obj) {
    if (typeof obj[key] === 'object') {
      let result = findProperty(obj[key], propName);
      if (result !== null) {
        return result;
      }
    }
  }
  
  return null;
}

// 示例对象
let person = {
  name: 'John',
  age: 30,
  address: {
    city: 'New York',
    country: 'USA'
  }
};

// 查找对象属性
console.log(findProperty(person, 'name')); // 输出：John
console.log(findProperty(person, 'city')); // 输出：New York
console.log(findProperty(person, 'country')); // 输出：USA
console.log(findProperty(person, 'salary')); // 输出：null