Javascript筛选对象数组

Question

我需要获得的模块，与那些张贴的地方等于“维也纳”，我无法消除那些没有通过验证。

这是JSON。

const json = [
   {
      "title":"Module A",
      "postings":[
         {"name": "1", "categories":{"location":"Viena"},},
         {"name": "2", "categories":{"location":"Paris"},},
         {"name": "3", "categories":{"location":"Viena"},},
        ]
   },
   {
      "title":"Module B",
      "postings":[
         {"name": "1", "categories":{"location":"Madrid"},},
         {"name": "3", "categories":{"location":"Paris"},},
        ]
   },
   {
      "title":"Module C",
      "postings":[
         {"name": "1", "categories":{"location":"Madrid"},},
         {"name": "2", "categories":{"location":"Viena"},},
        ]
   },  
];

预期结果

[
  {
      "title":"Module A",
      "postings":[
         {"name": "1", "categories":{"location":"Viena"},},
         {"name": "3", "categories":{"location":"Viena"},},
        ]
   },
   {
      "title":"Module C",
      "postings":[
         {"name": "2", "categories":{"location":"Viena"},},
        ]
   },  
];

这就是我正在尝试的

const result = json
.filter(module => module.postings
.filter(posting => posting.categories.location === 'Viena').length);

实际结果

我无法删除那些不符合条件的帖子。

Answer 1

我用reduce函数找到了一个快速的解决方案。

json.reduce((acc, curr) => {
    curr.postings = curr.postings.filter(e => e.categories.location == "Viena")
    if(curr.postings.length > 0)
        acc.push(curr);
    return acc;
}, []);

如果您想了解有关该函数更多信息，可以在以下站点找到：https://developer.mozilla.org/de/docs/web/javascript/reference/global_objects/array/reduce

Answer 2

filter需要返回一个真实的值-因此您应该在其中使用某些而不是另一个filter

null

const json = [
   {
      "title":"Module A",
      "postings":[
         {"name": "1", "categories":{"location":"Viena"},},
         {"name": "2", "categories":{"location":"Paris"},},
         {"name": "3", "categories":{"location":"Viena"},},
        ]
   },
   {
      "title":"Module B",
      "postings":[
         {"name": "1", "categories":{"location":"Madrid"},},
         {"name": "3", "categories":{"location":"Paris"},},
        ]
   },
   {
      "title":"Module C",
      "postings":[
         {"name": "1", "categories":{"location":"Madrid"},},
         {"name": "2", "categories":{"location":"Viena"},},
        ]
   },  
];

var result = json.filter(x => x.postings.some(p => p.categories.location == "Viena"));

console.log(result);