Question

我在后端工作，我有一个大数据的列表，我有另一个列表，我想找到它存在于biiger列表或不。如果它存在那么它应该返回空数组，否则它应该只返回唯一元素。我的大清单是这样的：

[ { name: 'Kapil',
    _id: 59ffb40d62d346204e09c0c1,
    tags: [] },
  { name: 'Nitin',
    _id: 59ffb40d62d346204e09c0d9,
    tags: [] },
  { name: 'Rakesh',
    _id: 5a0180b0d76afa5eaa79db05,
    tags: [] },
{much more} ]

和我希望在更大的列表中找到它的列表：

[{ name: 'Neelesh',
   _id: 59ffb40d62d346204easdwd9,
   tags: [] },
 { name: 'Rakesh',
  _id: 5a0180b0d76afa5eaa79db05,
  tags: [] }]

然后它应该只返回这个结果：

{ name: 'Neelesh',
       _id: 59ffb40d62d346204easdwd9,
       tags: [] }

因为它不在大名单中。我的lodash脚本是这样的：

_.filter(my_given_list,(item) => (_.find(bigger_list,{name:item.name})))

但它没有给出我预期的结果。我在哪里做错了？

Answer 1

正如@charlietfl所说，它应该是!_.find(..来过滤已经在大列表中的项目。我跑了那个代码并且效果很好。

var bigList = 
    [ 
      { 
        name: 'Kapil',
        _id: "59ffb40d62d346204e09c0c1",
        tags: [] 
      },
      { 
        name: 'Nitin',
        _id: "59ffb40d62d346204e09c0d9",
        tags: [] 
      },
      { 
        name: 'Rakesh',
        _id: "5a0180b0d76afa5eaa79db05",
        tags: [] 
      }
 ]

var myList = 
    [
      { 
        name: 'Neelesh',
       _id: "59ffb40d62d346204easdwd9",
       tags: [] 
      },
      { 
      name: 'Rakesh',
      _id: "5a0180b0d76afa5eaa79db05",
      tags: [] 
      }
    ]

var result = _.filter( myList,
                      ( item ) => ( !_.find( bigList, { name:item.name } ) )
                     )

console.log( result )

结果

[[object Object] {
  _id: "59ffb40d62d346204easdwd9",
  name: "Neelesh",
  tags: []
}]

Fiddle

Answer 2

您可以使用_.differenceBy()（在您的情况下为name或_id）查找myList中存在的项目，但不要退出bigList ：

var bigList = [{"name":"Kapil","_id":"59ffb40d62d346204e09c0c1","tags":[]},{"name":"Nitin","_id":"59ffb40d62d346204e09c0d9","tags":[]},{"name":"Rakesh","_id":"5a0180b0d76afa5eaa79db05","tags":[]}]
var myList = [{"name":"Neelesh","_id":"59ffb40d62d346204easdwd9","tags":[]},{"name":"Rakesh","_id":"5a0180b0d76afa5eaa79db05","tags":[]}]
  
var result = _.differenceBy(myList, bigList, '_id')

console.log(result)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

如何使用lodash从大列表中筛选列表？

2 个答案: