重构groupByDate函数：仅返回含非空数组的分组结果

原始数据与代码 #

待处理数据 #

const data = [
  {
    date: "2022-11-30T07:33:07.992955008Z",
    reponame: "test-repo",
    category: "veggy",
  },
  {
    date: "2022-11-30T07:33:07.992956372Z",
    reponame: "veggy-repo",
    category: "fruit",
  },
  {
    date: "2022-11-30T07:33:07.992956372Z",
    reponame: "veggy-repo",
    category: "veggy",
  },
  {
    date: "2022-11-30T07:33:07.992956372Z",
    reponame: "vegy-repo",
    category: "vegy",
  },
];

原始groupByDate函数 #

const moment = require('moment')

const monthsAcc = [{'January':[]}, {'February':[]}, {'March':[]}, {'April':[]}, {'May':[]}, {'June':[]}, {'July':[]}, {'August':[]}, {'September':[]}, {'October':[]}, {'November':[]}, {'December':[]}]

const groupByDate = (data) => {
  return data.reduce((acc, currentValue) => {
    const month = moment(currentValue["date"]).format('MMMM');
    const monthInAcc = acc.find((item)=>Object.keys(item).includes(month));
    monthInAcc[month].push(currentValue)
  return acc;
  }, monthsAcc);
};

console.log(groupByDate(seb)) // 注：此处seb为笔误，应为data

需求 #

1. 返回结果仅包含值为非空数组的月份项
2. 移除初始的monthsAcc累加数组
3. 接受其他重构建议

优化方案 #

方案1：返回对象格式（性能更优） #

用普通对象作为累加器，自动生成有数据的月份，最后过滤空数组：

const moment = require('moment')

const groupByDate = (data) => {
  // 空对象作为初始累加器，避免冗余月份初始化
  const grouped = data.reduce((acc, item) => {
    const month = moment(item.date).format('MMMM');
    // 不存在则初始化空数组
    if (!acc[month]) {
      acc[month] = [];
    }
    acc[month].push(item);
    return acc;
  }, {});

  // 过滤掉空数组的键，仅保留有数据的月份
  return Object.fromEntries(
    Object.entries(grouped).filter(([_, items]) => items.length > 0)
  );
};

console.log(groupByDate(data));

输出结果：

{
  November: [
    { date: '2022-11-30T07:33:07.992955008Z', reponame: 'test-repo', category: 'veggy' },
    { date: '2022-11-30T07:33:07.992956372Z', reponame: 'veggy-repo', category: 'fruit' },
    { date: '2022-11-30T07:33:07.992956372Z', reponame: 'veggy-repo', category: 'veggy' },
    { date: '2022-11-30T07:33:07.992956372Z', reponame: 'vegy-repo', category: 'vegy' }
  ]
}

方案2：返回数组格式（贴近原结构） #

如果需要保持原函数的数组结构（每个元素为单键对象），可在分组后转换：

const moment = require('moment')

const groupByDate = (data) => {
  const grouped = data.reduce((acc, item) => {
    const month = moment(item.date).format('MMMM');
    if (!acc[month]) {
      acc[month] = [];
    }
    acc[month].push(item);
    return acc;
  }, {});

  // 转换为数组格式，仅保留非空分组
  return Object.entries(grouped)
    .filter(([_, items]) => items.length > 0)
    .map(([month, items]) => ({ [month]: items }));
};

console.log(groupByDate(data));

输出结果：

[
  {
    November: [
      { date: '2022-11-30T07:33:07.992955008Z', reponame: 'test-repo', category: 'veggy' },
      { date: '2022-11-30T07:33:07.992956372Z', reponame: 'veggy-repo', category: 'fruit' },
      { date: '2022-11-30T07:33:07.992956372Z', reponame: 'veggy-repo', category: 'veggy' },
      { date: '2022-11-30T07:33:07.992956372Z', reponame: 'vegy-repo', category: 'vegy' }
    ]
  }
]

重构亮点 #

• 移除冗余的monthsAcc数组，避免初始化未使用的月份
• 用对象替代数组作为累加器，月份查找复杂度从O(n)降至O(1)，性能提升
• 自动过滤空数组，仅保留有数据的分组
• 修复原代码中console.log的笔误
• 简化逻辑，代码可读性更强

内容的提问来源于stack exchange，提问作者AlexUA