对对象数组进行排序并取 N 个元素答案

【问题标题】：Sort an array of Objects and take N elements对对象数组进行排序并取 N 个元素
【发布时间】：2019-04-10 00:59:13
【问题描述】：

在 NodeJS 服务中，我有一个包含具有以下属性的对象的数组：

batchType：字符串
batchId：字符串（是一个哈希）
transactionId：字符串（它是一个哈希）

这个数组存储了不同批次的所有交易。

基本上我需要的是能够从数组中获取 N 个项目，但要遵守某些规则：

每种批次至少获得 1 件商品
每个 batchId 至少获得 1 个项目
有时数组可能只有一种类型的批次

这是数组的一个例子：

let batchTransactionsArray = [
  { batchType: 'type1', batchId: '123', transactionId: 'ffasf23' },
  { batchType: 'type1', batchId: '312', transactionId: '423' },
  { batchType: 'type1', batchId: '123', transactionId: '534' },
  { batchType: 'type1', batchId: '312', transactionId: '86' },
  { batchType: 'type2', batchId: '111', transactionId: '97' },
  { batchType: 'type1', batchId: '312', transactionId: '1945' },
  { batchType: 'type1', batchId: '123', transactionId: '79' },
  { batchType: 'type1', batchId: '312', transactionId: '79' },
  { batchType: 'type3', batchId: '425', transactionId: '1555645' },
  { batchType: 'type1', batchId: '123', transactionId: 'fg5' },
  { batchType: 'type1', batchId: '123', transactionId: 'jkh5' },
  { batchType: 'type1', batchId: '312', transactionId: '53j' },
  { batchType: 'type1', batchId: '111', transactionId: '4545' },
  { batchType: 'type2', batchId: '111', transactionId: '534l' },
  { batchType: 'type1', batchId: '111', transactionId: 'jkg435' },
  { batchType: 'type1', batchId: '111', transactionId: 'gfxg23' },
  { batchType: 'type1', batchId: '111', transactionId: '7asdt' },
  { batchType: 'type1', batchId: '222', transactionId: 'jdsa7' },
  { batchType: 'type3', batchId: '663', transactionId: '12423445' },
  { batchType: 'type1', batchId: '111', transactionId: '89saf6' },
  { batchType: 'type1', batchId: '111', transactionId: '12h3g' },
  { batchType: 'type1', batchId: '111', transactionId: '4h3k2hj' },
  { batchType: 'type3', batchId: '663', transactionId: '145' }
];

我需要的输出示例是（如果我想要数组中的 5 个事务）：

[{ batchType: 'type1', batchId: '123', transactionId: '534' },
 { batchType: 'type1', batchId: '312', transactionId: '86' },
 { batchType: 'type2', batchId: '111', transactionId: '97' },
 { batchType: 'type2', batchId: '111', transactionId: '534l' },
 { batchType: 'type3', batchId: '663', transactionId: '145' }
]

transactionIds 的排序标准是随机的，没有特定的顺序要满足。

我尝试了一些 lodash 函数，例如 groupBy 和 sortBy，但还没有成功。

这是一个 jsfiddle，如果我在玩这个：https://jsfiddle.net/20jh3ze7/

非常感谢您的建议。

【问题讨论】：

请添加您尝试过的和无效的。
谢谢，我添加了一个 jsfiddle 链接
如果您需要 5 个项目，但 unqi id 超过 5 个，我们是否会超过 5 个最大项目或将其删除
谢谢合作过的各位，我会审核和测试你们的建议，让你们知道。再次感谢。

标签： javascript arrays node.js sorting lodash

【解决方案1】：

你可以用 lodash 做这样的事情：

let data = [ { batchType: 'type1', batchId: '123', transactionId: 'ffasf23' }, { batchType: 'type1', batchId: '312', transactionId: '423' }, { batchType: 'type1', batchId: '123', transactionId: '534' }, { batchType: 'type1', batchId: '312', transactionId: '86' }, { batchType: 'type2', batchId: '111', transactionId: '97' }, { batchType: 'type1', batchId: '312', transactionId: '1945' }, { batchType: 'type1', batchId: '123', transactionId: '79' }, { batchType: 'type1', batchId: '312', transactionId: '79' }, { batchType: 'type3', batchId: '425', transactionId: '1555645' }, { batchType: 'type1', batchId: '123', transactionId: 'fg5' }, { batchType: 'type1', batchId: '123', transactionId: 'jkh5' }, { batchType: 'type1', batchId: '312', transactionId: '53j' }, { batchType: 'type1', batchId: '111', transactionId: '4545' }, { batchType: 'type2', batchId: '111', transactionId: '534l' }, { batchType: 'type1', batchId: '111', transactionId: 'jkg435' }, { batchType: 'type1', batchId: '111', transactionId: 'gfxg23' }, { batchType: 'type1', batchId: '111', transactionId: '7asdt' }, { batchType: 'type1', batchId: '222', transactionId: 'jdsa7' }, { batchType: 'type3', batchId: '663', transactionId: '12423445' }, { batchType: 'type1', batchId: '111', transactionId: '89saf6' }, { batchType: 'type1', batchId: '111', transactionId: '12h3g' }, { batchType: 'type1', batchId: '111', transactionId: '4h3k2hj' }, { batchType: 'type3', batchId: '663', transactionId: '145' } ];

const customTake = (d, n) => {
  const roundRobinUnion = (arr) => {
    let res = []
    while (_.flatten(arr).length)
      _.each(arr, x => x.length ? res.push(_.remove(x, (y, i) => i == 0)) : null)
    return _.flatten(res)
  }
  const groups = _(d)
    .orderBy(['batchType', 'batchId'])
    .groupBy('batchType')
    .mapValues(x => _.values(_.groupBy(x, 'batchId')))
    .map(x => roundRobinUnion(x))
    .value()
  return _.take(roundRobinUnion(groups), n)
}

console.log(customTake(data, 3))
console.log(customTake(data, 5))
console.log(customTake(data, 6))
console.log(customTake(data, 8))

&lt;script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.10/lodash.min.js"&gt;&lt;/script&gt;

我们的想法是按batchType 和batchId 进行分组，并将此问题视为循环联合。您遍历每个数组索引并对每个元素进行联合。

如果您关心结束排序顺序，您可以随时在最后执行另一个 orderBy 等。

以下是roundRobinUnion 理念的简单示例：

const data = [
  [1, 2, 3],
  [1],
  [5, 6]
]

const roundRobinUnion = (arr) => {
  let res = []
  while (_.flatten(arr).length)
    _.each(arr, x => x.length ? res.push(_.remove(x, (y, i) => i == 0)) : null)
  return _.flatten(res)
}

console.log(roundRobinUnion(data))  // [1,1,5,2,6,3]

&lt;script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.10/lodash.min.js"&gt;&lt;/script&gt;

【讨论】：

很好，这比我的干净得多
这很酷，但是这如何满足第二个要求：每个batchId至少获得1个项目？
好问题。已更新以解决您的问题。

【解决方案2】：

您可以分步进行：

首先添加唯一的batchType元素（这符合第一个标准）
然后添加唯一的 batchId 元素（这符合第二个标准）
如果还有剩余空间（最多 N 个元素），则用剩余元素填充数组

要检查唯一性，您可以使用Set。既然您说您使用的是 lodash，您可以使用 _.groupBy 将您的数组按 batchItem 和 batchId 分组，以从每个组中获取唯一元素。

let batchTransactionsArray = [
  { batchType: 'type1', batchId: '123', transactionId: 'ffasf23' },
  { batchType: 'type1', batchId: '312', transactionId: '423' },
  { batchType: 'type1', batchId: '123', transactionId: '534' },
  { batchType: 'type1', batchId: '312', transactionId: '86' },
  { batchType: 'type2', batchId: '111', transactionId: '97' },
  { batchType: 'type1', batchId: '312', transactionId: '1945' },
  { batchType: 'type1', batchId: '123', transactionId: '79' },
  { batchType: 'type1', batchId: '312', transactionId: '79' },
  { batchType: 'type3', batchId: '425', transactionId: '1555645' },
  { batchType: 'type1', batchId: '123', transactionId: 'fg5' },
  { batchType: 'type1', batchId: '123', transactionId: 'jkh5' },
  { batchType: 'type1', batchId: '312', transactionId: '53j' },
  { batchType: 'type1', batchId: '111', transactionId: '4545' },
  { batchType: 'type2', batchId: '111', transactionId: '534l' },
  { batchType: 'type1', batchId: '111', transactionId: 'jkg435' },
  { batchType: 'type1', batchId: '111', transactionId: 'gfxg23' },
  { batchType: 'type1', batchId: '111', transactionId: '7asdt' },
  { batchType: 'type1', batchId: '222', transactionId: 'jdsa7' },
  { batchType: 'type3', batchId: '663', transactionId: '12423445' },
  { batchType: 'type1', batchId: '111', transactionId: '89saf6' },
  { batchType: 'type1', batchId: '111', transactionId: '12h3g' },
  { batchType: 'type1', batchId: '111', transactionId: '4h3k2hj' },
  { batchType: 'type3', batchId: '663', transactionId: '145' }
];

function getNItems(array, N = 5) {
  if (N >= array.length) return array;
  let batchTypeGroups = _.groupBy(array, e => e.batchType),
      res  = new Set(), batchIds = new Set();
  
  // add unique batchTypes
  for (let [batchType, elements] of Object.entries(batchTypeGroups)) {
    if (res.size === N) break;
    let d = elements.find(e => !batchIds.has(e.batchId));
    if (d) {
      res.add(d);
      batchIds.add(d.batchId);
    } else {
      res.add(elements[0]);
    }
  }
  
  // add remaining unique batchIds
  let batchIdGroups = _.groupBy(array.filter(e => !batchIds.has(e.batchId)), e => e.batchId);
  for (let [batchId, elements] of Object.entries(batchIdGroups)) {
    if (res.size === N) break;
    res.add(elements[0]);
  }
  
  // add any remaining elements until we have N elements
  for (let e of array) {
    if (res.size === N) break;
    res.add(e);
  }
  
  return Array.from(res);
}

console.log(getNItems(batchTransactionsArray, 5));

&lt;script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.min.js"&gt;&lt;/script&gt;

【讨论】：

谢谢，我将此标记为正确答案，因为它满足我的所有需求，也很容易调整和适应我的项目。
@VíctorVíquez 酷。但是，我认为我有一个错误。我已经用更正更新了我的答案（第一个 for 循环中的 else 语句）。
是的！你说的对。我以前没见过。谢谢。

【解决方案3】：

我认为对于这类问题我们不需要额外的依赖。

我们可以通过普通的 javascript 来实现 :)

let batchTransactionsArray = [
  { batchType: "type1", batchId: "123", transactionId: "ffasf23" },
  { batchType: "type1", batchId: "312", transactionId: "423" },
  { batchType: "type1", batchId: "123", transactionId: "534" },
  { batchType: "type1", batchId: "312", transactionId: "86" },
  { batchType: "type2", batchId: "111", transactionId: "97" },
  { batchType: "type1", batchId: "312", transactionId: "1945" },
  { batchType: "type1", batchId: "123", transactionId: "79" },
  { batchType: "type1", batchId: "312", transactionId: "79" },
  { batchType: "type3", batchId: "425", transactionId: "1555645" },
  { batchType: "type1", batchId: "123", transactionId: "fg5" },
  { batchType: "type1", batchId: "123", transactionId: "jkh5" },
  { batchType: "type1", batchId: "312", transactionId: "53j" },
  { batchType: "type1", batchId: "111", transactionId: "4545" },
  { batchType: "type2", batchId: "111", transactionId: "534l" },
  { batchType: "type1", batchId: "111", transactionId: "jkg435" },
  { batchType: "type1", batchId: "111", transactionId: "gfxg23" },
  { batchType: "type1", batchId: "111", transactionId: "7asdt" },
  { batchType: "type1", batchId: "222", transactionId: "jdsa7" },
  { batchType: "type3", batchId: "663", transactionId: "12423445" },
  { batchType: "type1", batchId: "111", transactionId: "89saf6" },
  { batchType: "type1", batchId: "111", transactionId: "12h3g" },
  { batchType: "type1", batchId: "111", transactionId: "4h3k2hj" },
  { batchType: "type3", batchId: "663", transactionId: "145" }
];

const getUniqueBatches = () => {
  const uniqueBatches = [];

  batchTransactionsArray.forEach(b => {
    const batchByType = uniqueBatches.find(findBatchByType(b.batchType));
    const batchById = uniqueBatches.find(findBatchByBatchId(b.batchId));
    if (!batchByType || !batchById) {
      uniqueBatches.push(b);
    }
  });

  return uniqueBatches;
};

const findBatchByType = batchType => {
  return batch => {
    return batch.batchType === batchType;
  };
};
const findBatchByBatchId = batchId => {
  return batch => {
    return batch.batchId === batchId;
  };
};

console.log(getUniqueBatches());

【讨论】：