如何在typescript中对对象上的项进行分组和计数？

interface Student {
  name: string;
  grade: number;
}

const students: Student[] = [
  { name: 'Alice', grade: 1 },
  { name: 'Bob', grade: 2 },
  { name: 'Charlie', grade: 1 },
  { name: 'David', grade: 3 },
  { name: 'Eve', grade: 2 },
];

const groupedCounts = students.reduce((acc, student) => {
  const { grade } = student;
  
  // 如果该年级还没有被分组，则创建一个新的分组
  if (!acc[grade]) {
    acc[grade] = {
      count: 0,
      students: [],
    };
  }
  
  // 将学生添加到对应年级的分组中，并增加计数
  acc[grade].students.push(student);
  acc[grade].count++;
  
  return acc;
}, {} as { [grade: number]: { count: number, students: Student[] } });

console.log(groupedCounts);

{
  1: { count: 2, students: [ { name: 'Alice', grade: 1 }, { name: 'Charlie', grade: 1 } ] },
  2: { count: 2, students: [ { name: 'Bob', grade: 2 }, { name: 'Eve', grade: 2 } ] },
  3: { count: 1, students: [ { name: 'David', grade: 3 } ] }
}