将v模型与groupBy数组一起使用，返回平面数组

function groupBy(arr, key) {
  return arr.reduce((result, item) => {
    const groupKey = item[key];
    if (!result[groupKey]) {
      result[groupKey] = [];
    }
    result[groupKey].push(item);
    return result;
  }, {});
}

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

const flatArray = Object.values(groupedData).flatMap(group => group);
console.log(flatArray);

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