js group by

以下是两种JavaScript实现分组的方法：

1.使用reduce()方法实现分组

const data = [
 { name: 'apple', type: 'fruit' },
  { name: 'banana', type: 'fruit' },
  { name: 'carrot', type: 'vegetable' },
  { name: 'potato', type: 'vegetable' },
  { name: 'orange', type: 'fruit' },
  { name: 'broccoli', type: 'vegetable' },
];

const groupedData = data.reduce((result, item) => {
  const key = item.type;
  if (!result[key]) {
    result[key] = [];
  }
  result[key].push(item);
  return result;
}, {});

console.log(groupedData);
// 输出：
// {
//   fruit: [
//     { name: 'apple', type: 'fruit' },
//     { name: 'banana', type: 'fruit' },
//     { name: 'orange', type: 'fruit' }
//   ],
//   vegetable: [
//     { name: 'carrot', type: 'vegetable' },
//     { name: 'potato', type: 'vegetable' },
//     { name: 'broccoli', type: 'vegetable' }
//   ]
// }

2.使用自定义函数实现分组

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

const data = [
  { name: 'apple', type: 'fruit' },
  { name: 'banana', type: 'fruit' },
  { name: 'carrot', type: 'vegetable' },
  { name: 'potato', type: 'vegetable' },
  { name: 'orange', type: 'fruit' },
  { name: 'broccoli', type: 'vegetable' },
];

const groupedData = groupBy(data, 'type');

console.log(groupedData);
// 输出：
// {
//   fruit: [
//     { name: 'apple', type: 'fruit' },
//     { name: 'banana', type: 'fruit' },
//     { name: 'orange', type: 'fruit' }
//   ],
//   vegetable: [
//     { name: 'carrot', type: 'vegetable' },
//     { name: 'potato', type: 'vegetable' },
//     { name: 'broccoli', type: 'vegetable' }
//   ]
// }