查找嵌套JavaScript对象中空属性的长度

function countEmptyProperties(obj) {
  let count = 0;
  
  for (let key in obj) {
    if (obj.hasOwnProperty(key)) {
      if (typeof obj[key] === "object" && obj[key] !== null) {
        count += countEmptyProperties(obj[key]); // 递归遍历嵌套对象
      } else if (!obj[key]) {
        count++; // 属性为空，计数器加一
      }
    }
  }
  
  return count;
}

const data = {
  name: "John",
  age: 30,
  address: {
    street: "123 Main St",
    city: "",
    country: "USA",
    postalCode: null
  },
  email: ""
};

const emptyPropertiesLength = countEmptyProperties(data);
console.log(emptyPropertiesLength); // 输出 3