在JavaScript中，有没有一种优雅的方法来合并两个对象并对任何公共属性求和？

function mergeObjects(obj1, obj2) {
  const merged = { ...obj1, ...obj2 };
  const keys = Object.keys(merged);

  return keys.reduce((result, key) => {
    if (typeof obj1[key] === 'number' && typeof obj2[key] === 'number') {
      result[key] = obj1[key] + obj2[key];
    } else {
      result[key] = obj2[key] || obj1[key];
    }

    return result;
  }, {});
}

// 示例用法
const obj1 = { a: 1, b: 2, c: 3 };
const obj2 = { b: 3, c: 4, d: 5 };
const mergedObj = mergeObjects(obj1, obj2);

console.log(mergedObj); // { a: 1, b: 5, c: 7, d: 5 }