Node.js中多嵌套数组按class_id分组合并学生数据求助

原始数据 #

[
  [
    { class_id: "Grade 1", roll_number: "1", name: "alex" },
    { class_id: "Grade 1", roll_number: "2", name: "bob" },
  ],
  [
    { class_id: "Grade 2", roll_number: "7", name: "peter" },
    { class_id: "Grade 3", roll_number: "6", name: "lia" },
    { class_id: "Grade 2", roll_number: "5", name: "mary" },
    { class_id: "Grade 3", roll_number: "1", name: "violet" },
  ],
]

需求格式 #

[
  {
    class_id: "Grade 1",
    students: [
      { roll_number: "1", name: "alex" },
      { roll_number: "2", name: "bob" },
    ],
  },
  {
    class_id: "Grade 2",
    students: [
      { roll_number: "7", name: "peter" },
      { roll_number: "5", name: "mary" },
    ],
  },
  {
    class_id: "Grade 3",
    students: [
      { roll_number: "6", name: "lia" },
      { roll_number: "1", name: "violet" },
    ],
  },
]

现有代码问题 #

你尝试的代码存在两个核心问题：

• 假设每个子数组仅对应一个class_id，无法处理同一子数组内多个不同class_id的情况
• 输出的字段名是studentsList，和需求的students不匹配

现有代码：

var response = [];
data.map(item => {
  var students = [];
  for (var i = 0; i < item.length; i++) {
    const stu_obj = {
      name: item[i].name,
      roll_number: item[i].roll_number,
    };
    students.push(stu_obj);
    if (i == 0) {
      const class_obj = {
        class_id: item[0].class_id,
        studentsList: students,
      };
      response.push(class_obj);
      continue;
    }
  }
});

解决方案 #

步骤说明 #

1. 扁平化嵌套数组：先把两层嵌套的学生数组转换成一维数组，统一处理所有学生对象
2. 按class_id分组：使用临时对象存储每个班级对应的学生列表
3. 转换为目标格式：把分组后的对象转成需求的数组结构

代码实现 #

// 扁平化嵌套数组（现代环境支持）
const flattenedData = data.flat();

// 按class_id分组
const classGroups = flattenedData.reduce((groups, student) => {
  // 解构出class_id和剩余的学生信息
  const { class_id, ...studentInfo } = student;
  // 如果当前班级不存在，初始化空数组
  if (!groups[class_id]) {
    groups[class_id] = [];
  }
  // 添加学生信息到对应班级
  groups[class_id].push(studentInfo);
  return groups;
}, {});

// 转换为目标数组格式
const result = Object.entries(classGroups).map(([class_id, students]) => ({
  class_id,
  students
}));

console.log(result);

兼容低版本环境的扁平化方案 #

如果运行环境不支持Array.flat()，可以用reduce手动扁平化：

const flattenedData = data.reduce((acc, subArray) => acc.concat(subArray), []);

内容的提问来源于stack exchange，提问作者sumitra_gangula