给定一个对象数组，计算定义了多少个(可能不同)属性

function countDistinctProperties(objArray) {
  let properties = new Set();

  for (let obj of objArray) {
    for (let prop in obj) {
      properties.add(prop);
    }
  }

  return properties.size;
}

// 示例用法
const objArray = [
  { name: 'John', age: 25, city: 'New York' },
  { name: 'Jane', age: 30, country: 'Canada' },
  { name: 'Bob', profession: 'Engineer' }
];

const distinctPropertiesCount = countDistinctProperties(objArray);
console.log(distinctPropertiesCount); // 输出：5