如何使用 lodash 从对象数组中获取不同的元素（不区分大小写）

Question

我有一个如下所示的数组，

[
  {
    "_id": "5e3ccb88c9b3027ef4977894",
    "name": "microsoft"
  },
  {
    "_id": "59ce020caa87df4da0ee2c77",
    "name": "Microsoft"
  },
  {
    "_id": "5e077c78bc0d663d7170ba1c",
    "name": "MICROSOFT"
  },
  {
    "_id": "608839e8d9271457814a7aa4",
    "name": "Microsoft "
  },
  {
    "_id": "5ecd46657ffa9b761a0e41cd",
    "name": "Microsoft  - MSN"
  },
  {
    "_id": "5dfb47adbc0d663d716fe25f",
    "name": "Microsoft  Alumni Foundation"
  }
]

现在我只需要一个 Microsoft，而不是使用 lodash 的这些案例组合。

预期输出，

[
  {
    "_id": "608839e8d9271457814a7aa4",
    "name": "Microsoft "
  },
  {
    "_id": "5ecd46657ffa9b761a0e41cd",
    "name": "Microsoft  - MSN"
  },
  {
    "_id": "5dfb47adbc0d663d716fe25f",
    "name": "Microsoft  Alumni Foundation"
  }
]

谁能帮我解决这个问题？找到了很多解决方案，但我需要不区分大小写的过滤器。

提前致谢。

Answer 1

您可以使用 _.filter, _.toLower and _.trim 来执行此操作。

我们可以保留 seen Set() 个值，这样我们就知道我们以前看过哪些项目。在添加或检查此集合之前使用 _.toLower 和 _.trim 我们可以确保该项目不是数组中另一项目的微小变化。

像这样：

let data = [ { _id: '5e3ccb88c9b3027ef4977894', name: 'microsoft' }, { _id: '59ce020caa87df4da0ee2c77', name: 'Microsoft' }, { _id: '5e077c78bc0d663d7170ba1c', name: 'MICROSOFT' }, { _id: '608839e8d9271457814a7aa4', name: 'Microsoft ' }, { _id: '5ecd46657ffa9b761a0e41cd', name: 'Microsoft  - MSN' }, { _id: '5dfb47adbc0d663d716fe25f', name: 'Microsoft  Alumni Foundation' }, ];

const testPrefixes = new Set();

let res = _.filter(data, (o) => {
  if (testPrefixes.has(_.trim(_.toLower(o.name)))) return false;
  else return testPrefixes.add(_.trim(_.toLower(o.name)));
});

console.log(res);

<script src="https://cdn.jsdelivr.net/npm/lodash@4.17.21/lodash.min.js"></script>

Answer 2

这是我随身携带的一个无库实用程序（在 TypeScript 中）：

const dedupeArrayBy = <T, TK>(items: T[], selector: (item: T) => TK): T[] => {
    const m = new Map(items.map((item) => [selector(item), item] as const));
    return [...m.values()];
};

所以你可以：

const deduped = dedupeArrayBy(items, v => v.name.trim().toLowerCase());

这是Javascript翻译：

"use strict";
const dedupeArrayBy = (items, selector) => {
  const m = new Map(items.map((item) => [selector(item), item]));
  return [...m.values()];
};
let data = [{
  _id: '5e3ccb88c9b3027ef4977894',
  name: 'microsoft'
}, {
  _id: '59ce020caa87df4da0ee2c77',
  name: 'Microsoft'
}, {
  _id: '5e077c78bc0d663d7170ba1c',
  name: 'MICROSOFT'
}, {
  _id: '608839e8d9271457814a7aa4',
  name: 'Microsoft '
}, {
  _id: '5ecd46657ffa9b761a0e41cd',
  name: 'Microsoft  - MSN'
}, {
  _id: '5dfb47adbc0d663d716fe25f',
  name: 'Microsoft  Alumni Foundation'
}, ];
console.log(dedupeArrayBy(data, v => v.name.trim().toLowerCase()));

Answer 3

您可以使用 lodash 的 _.uniqBy()，它接受一个生成匹配条件的函数。在这种情况下 trim 字符串，并将其转换为小写：

const arr = [{"_id":"5e3ccb88c9b3027ef4977894","name":"microsoft"},{"_id":"59ce020caa87df4da0ee2c77","name":"Microsoft"},{"_id":"5e077c78bc0d663d7170ba1c","name":"MICROSOFT"},{"_id":"608839e8d9271457814a7aa4","name":"Microsoft "},{"_id":"5ecd46657ffa9b761a0e41cd","name":"Microsoft  - MSN"},{"_id":"5dfb47adbc0d663d716fe25f","name":"Microsoft  Alumni Foundation"}]

const result = _.uniqBy(arr, o => o.name.trim().toLowerCase())

console.log(result)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.21/lodash.min.js" integrity="sha512-WFN04846sdKMIP5LKNphMaWzU7YpMyCU245etK3g/2ARYbPK9Ub18eG+ljU96qKRCWh+quCY7yefSmlkQw1ANQ==" crossorigin="anonymous" referrerpolicy="no-referrer"></script>

因为你想要一系列重复中的最后一项，你可以反转数组，得到唯一的项目，然后反转回来：

const arr = [{"_id":"5e3ccb88c9b3027ef4977894","name":"microsoft"},{"_id":"59ce020caa87df4da0ee2c77","name":"Microsoft"},{"_id":"5e077c78bc0d663d7170ba1c","name":"MICROSOFT"},{"_id":"608839e8d9271457814a7aa4","name":"Microsoft "},{"_id":"5ecd46657ffa9b761a0e41cd","name":"Microsoft  - MSN"},{"_id":"5dfb47adbc0d663d716fe25f","name":"Microsoft  Alumni Foundation"}]

const result = _.reverse(_.uniqBy(
  _.reverse([...arr]), 
  o => o.name.trim().toLowerCase()
))

console.log(result)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.21/lodash.min.js" integrity="sha512-WFN04846sdKMIP5LKNphMaWzU7YpMyCU245etK3g/2ARYbPK9Ub18eG+ljU96qKRCWh+quCY7yefSmlkQw1ANQ==" crossorigin="anonymous" referrerpolicy="no-referrer"></script>

如何使用 lodash 从对象数组中获取不同的元素（不区分大小写）

How to get distinct elements(case insensitive) from array of objects using lodash

javascript

json

node.js

lodash