如何在嵌套数组的对象中按元素分组

function groupBy(arr, key) {
  const groups = {};
  
  arr.forEach(obj => {
    const groupKey = obj[key];
    
    if (!groups[groupKey]) {
      groups[groupKey] = [];
    }
    
    groups[groupKey].push(obj);
  });
  
  return groups;
}

const data = [
  { name: 'Alice', age: 25, gender: 'female' },
  { name: 'Bob', age: 30, gender: 'male' },
  { name: 'Charlie', age: 35, gender: 'male' },
  { name: 'Dave', age: 25, gender: 'male' },
  { name: 'Eve', age: 30, gender: 'female' }
];

const groupedData = groupBy(data, 'age');
console.log(groupedData);

{
  25: [
    { name: 'Alice', age: 25, gender: 'female' },
    { name: 'Dave', age: 25, gender: 'male' }
  ],
  30: [
    { name: 'Bob', age: 30, gender: 'male' },
    { name: 'Eve', age: 30, gender: 'female' }
  ],
  35: [
    { name: 'Charlie', age: 35, gender: 'male' }
  ]
}