如何修改现有函数实现按lastName和gender双属性分组数组对象

现有如下用户数组需要分组：

[
  {
    "name": "john",
    "lastName": "doe",
    "gender": "male"
  },
  {
    "name": "jane",
    "lastName": "doe",
    "gender": "female"
  },
  {
    "name": "peter",
    "lastName": "dickons",
    "gender": "male"
  },
  {
    "name": "eva",
    "lastName": "dickons",
    "gender": "female"
  }
]

目前已经实现了按单个属性分组的函数（JavaScript和TypeScript版本如下），现在需要修改函数，让它支持传入lastName和gender两个属性，实现按双属性分组。

现有单属性分组函数 #

JavaScript版本

const groupByObjectKey = (users, key) => {
  return users.reduce((rv, x) => {
    (rv[x[key]] = rv[x[key]] || []).push(x);
    return rv;
  }, {});
};

// 使用示例
let users = [/* 上述数组内容 */];
const usersGroupedByLastName = groupByObjectKey(users, "lastName");
console.log(usersGroupedByLastName);

TypeScript版本

interface User {
  name: string;
  lastName: string;
  gender: string;
}

const groupByObjectKey = (users: User[], key: string): Record<string, User[]> => {
    return users.reduce((rv, x) => {
        (rv[x[key]] = rv[x[key]] || []).push(x);
        return rv;
    }, {} as Record<string, User[]>);
};

// 使用示例
const users: User[] = [/* 上述数组内容 */];
const usersGroupedByLastName = groupByObjectKey(users, "lastName");

修改方案 #

下面提供两种常用的多属性分组实现方式，你可以根据需求选择：

方案1：使用复合字符串键分组

这种方式把多个属性值拼接成一个字符串作为分组键，实现简单，适合不需要嵌套结构的场景。

修改后的JavaScript函数：

const groupByKeys = (users, keys) => {
  return users.reduce((rv, x) => {
    // 用短横线拼接属性值生成复合键，也可以用其他分隔符（比如下划线）
    const groupKey = keys.map(key => x[key]).join('-');
    (rv[groupKey] = rv[groupKey] || []).push(x);
    return rv;
  }, {});
};

// 使用示例
const usersGroupedByLastNameAndGender = groupByKeys(users, ["lastName", "gender"]);
console.log(usersGroupedByLastNameAndGender);

输出结果：

{
  "doe-male": [{"name":"john","lastName":"doe","gender":"male"}],
  "doe-female": [{"name":"jane","lastName":"doe","gender":"female"}],
  "dickons-male": [{"name":"peter","lastName":"dickons","gender":"male"}],
  "dickons-female": [{"name":"eva","lastName":"dickons","gender":"female"}]
}

方案2：生成嵌套结构的分组结果

如果希望分组结果是嵌套对象（比如{ 姓氏: { 性别: [用户列表] } }），可以用下面的实现：

修改后的JavaScript函数：

const groupByNestedKeys = (users, keys) => {
  return users.reduce((rv, x) => {
    let currentLevel = rv;
    // 逐层遍历分组键，构建嵌套结构
    for (let i = 0; i < keys.length; i++) {
      const key = keys[i];
      const value = x[key];
      // 最后一个键直接对应用户数组
      if (i === keys.length - 1) {
        (currentLevel[value] = currentLevel[value] || []).push(x);
      } else {
        // 非最后一个键则创建嵌套对象
        currentLevel[value] = currentLevel[value] || {};
        currentLevel = currentLevel[value];
      }
    }
    return rv;
  }, {});
};

// 使用示例
const nestedGroupedUsers = groupByNestedKeys(users, ["lastName", "gender"]);
console.log(nestedGroupedUsers);

输出结果：

{
  "doe": {
    "male": [{"name":"john","lastName":"doe","gender":"male"}],
    "female": [{"name":"jane","lastName":"doe","gender":"female"}]
  },
  "dickons": {
    "male": [{"name":"peter","lastName":"dickons","gender":"male"}],
    "female": [{"name":"eva","lastName":"dickons","gender":"female"}]
  }
}

TypeScript版本的多属性分组函数 #

如果用TypeScript，可以给函数加上泛型，保证类型安全：

复合键版本

interface User {
  name: string;
  lastName: string;
  gender: string;
}

const groupByKeys = <T extends Record<string, any>>(items: T[], keys: (keyof T)[]): Record<string, T[]> => {
  return items.reduce((rv, item) => {
    const groupKey = keys.map(key => item[key]).join('-');
    (rv[groupKey] = rv[groupKey] || []).push(item);
    return rv;
  }, {} as Record<string, T[]>);
};

// 使用示例
const users: User[] = [/* 上述数组内容 */];
const groupedByTwoKeys = groupByKeys(users, ["lastName", "gender"]);

嵌套结构版本

const groupByNestedKeys = <T extends Record<string, any>>(items: T[], keys: (keyof T)[]): any => {
  return items.reduce((rv, item) => {
    let currentLevel: any = rv;
    for (let i = 0; i < keys.length; i++) {
      const key = keys[i];
      const value = item[key];
      if (i === keys.length - 1) {
        (currentLevel[value] = currentLevel[value] || []).push(item);
      } else {
        currentLevel[value] = currentLevel[value] || {};
        currentLevel = currentLevel[value];
      }
    }
    return rv;
  }, {});
};

// 使用示例
const nestedGrouped = groupByNestedKeys(users, ["lastName", "gender"]);

内容的提问来源于stack exchange，提问作者erol_smsr