JS 对象数组根据指定属性名group by分组

参考资料:

1. https://blog.csdn.net/mafan121/article/details/83418116
2. https://www.30secondsofcode.org/js/s/group-by

---

---

一. 分组方法1

• 可根据匿名函数或者属性名来分组

const groupByMethod1 = (arr, fnOrProperty) => {
    return arr.map(typeof fnOrProperty === 'function' ? fnOrProperty : val => val[fnOrProperty])
              .reduce((acc, val, i) => {
                acc[val] = (acc[val] || []).concat(arr[i]);
                return acc;
              }, {});
}

---

二. 分组方法2

• 可根据匿名函数来分组

const groupByMethod2 = (list, fn) => {
    const groups = {};
    list.forEach(function (o) {
        const group = JSON.stringify(fn(o));
        groups[group] = groups[group] || [];
        groups[group].push(o);
    });
    return groups;
}

---

三. 效果

• 数据准备

  const studentList = [
      {
          class: '1班',
          name: '张三',
          sex: '男'
      },
      {
          class: '2班',
          name: '李四',
          sex: '男'
      },
      {
          class: '1班',
          name: '王五',
          sex: '女'
      },
      {
          class: '3班',
          name: '赵六',
          sex: '男'
      }
  ];
  

• 效果

  // ⏹通过属性的方式,按照班级来分组
  const group1 = groupByMethod1(studentList, 'class');
  console.log(group1);
  /*
      {
          '1班': [
              {class: "1班", name: "张三", sex: "男"},
              {class: "1班", name: "王五", sex: "女"}
          ],
          '2班': [
              {class: "2班", name: "李四", sex: "男"}
          ],
          '3班': [
              {class: "3班", name: "赵六", sex: "男"}
          ],
      }
  */
  

  // ⏹通过匿名函数的方式1,按照性别来分组
  const group2 = groupByMethod1(studentList, (item) => item.sex);
  console.log(group2);
  /*
      {
          女: [
              {class: "1班", name: "王五", sex: "女"}
          ],
          男: [
              {class: "1班", name: "张三", sex: "男"},
              {class: "2班", name: "李四", sex: "男"},
              {class: "3班", name: "赵六", sex: "男"}
          ],
      }
  */
  console.log(group2['男']);
  /*
      [
          {class: "1班", name: "张三", sex: "男"},
          {class: "2班", name: "李四", sex: "男"},
          {class: "3班", name: "赵六", sex: "男"}
      ]
  */
  

  // ⏹通过匿名函数的方式2,按照性别来分组
  const group3 = groupByMethod2(studentList, (item) => item.sex);
  console.log(group3);
  /*
      {
          "女": [
              {class: "1班", name: "王五", sex: "女"}
          ],
          "男": [
              {class: "1班", name: "张三", sex: "男"},
              {class: "2班", name: "李四", sex: "男"},
              {class: "3班", name: "赵六", sex: "男"}
          ],
      }
  */
  
  // 通过这种方式的key来获取的时候,必须多套一层 ''
  console.log(group3['"男"']);
  /*
      [
          {class: "1班", name: "张三", sex: "男"},
          {class: "2班", name: "李四", sex: "男"},
          {class: "3班", name: "赵六", sex: "男"}
      ]
  */