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Question

请考虑以下数据：

{  
   post_views:[  
      {  
         id:1,
         post_id:5,
         ip_address:"xxx",
         created_at:"2016-08-08T22:22:45+0000",
         updated_at:"2016-08-08T22:22:45+0000"
      },
      {  
         id:2,
         post_id:5,
         ip_address:"yyy",
         created_at:"2016-08-08T22:23:00+0000",
         updated_at:"2016-08-08T22:23:00+0000"
      },
      ...
   ]
}

如何获得匹配的所有元素：2016-08-08 ??

您尝试了什么？

Lodashes，过滤器：

  let datesThatMatch = filter(this.state.data.post_views, (views) => {
    return moment(views.created_at).format('MMMM Do YYYY') === moment(views.created_at).format('MMMM Do YYYY')
  });

  console.log(datesThatMatch);

我不关心他们创建的时间，就像他们在比赛中创建的那一天一样。

帮助？

更新

我刚刚意识到我也是这样做的全部都是错的，因为虽然我只向你展示了一部分数据，但数组中有数百个这些对象（如果不是数千个），目标就是说，确定2016-08-08的16场比赛，x日期的50场比赛，y场的14场比赛，这增加了这个过滤器的复杂性。

Answer 1

我认为groupBy是基于您的更新的更好选择：

var data = {  
   post_views:[  
      {  
         id:1,
         post_id:5,
         ip_address:"xxx",
         created_at:"2016-08-08T22:22:45+0000",
         updated_at:"2016-08-08T22:22:45+0000"
      },
      {  
         id:2,
         post_id:5,
         ip_address:"yyy",
         created_at:"2016-08-08T22:23:00+0000",
         updated_at:"2016-08-08T22:23:00+0000"
      },
      {  
         id:3,
         post_id:5,
         ip_address:"zzz",
         created_at:"2016-08-12T20:15:00+0000",
         updated_at:"2016-08-12T21:20:00+0000"
      },
   ]
}
     
let groupedDatesThatMatch = _.groupBy(data.post_views, function(views) {
     return moment(views.created_at).format('MMMM Do YYYY')
});
     
console.log(groupedDatesThatMatch);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.14.2/lodash.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.14.1/moment.min.js"></script>

你从另一端得到一个数组对象

Answer 2

您可以构建“反向查找表”（即指示每个键出现的位置）以下是示例演示;

 var a = [1,1,2,3,4,5,6,6,7];                                                                                                                           
 var reverseIndex = new Map();
 a.every((cVal, i, a) => {
   var existing = reverseIndex.has(cVal) ? reverseIndex.get(cVal) : [];
   existing.push(i);
   reverseIndex.set(cVal, existing);
   return true;
 });

console.log(reverseIndex);

Answer 3

怎么样......

let post_views = [  
      {  
         id:1,
         post_id:5,
         ip_address:"xxx",
         created_at:"2016-08-08T22:22:45+0000",
         updated_at:"2016-08-08T22:22:45+0000"
      },
      {  
         id:2,
         post_id:5,
         ip_address:"yyy",
         created_at:"2016-08-08T22:23:00+0000",
         updated_at:"2016-08-08T22:23:00+0000"
      }
   ]
  
let looking_for = new RegExp('2016-08-08')
 
let result = post_views.filter(view => looking_for.test(view.created_at) || looking_for.test(view.updated_at) )

let summary = result.reduce((prev,view) => { 
  
                  let created_at = view.created_at.split('T')[0];  
                  let updated_at = view.updated_at.split('T')[0];
  
                      prev.created_at[created_at] = prev.created_at[created_at] || 0;
                      prev.updated_at[updated_at] = prev.updated_at[updated_at] || 0;
                      prev.created_at[created_at]++;
                      prev.updated_at[updated_at]++;
  
                      return prev;  
                  },{ created_at: {}, updated_at: {} })

console.log(result);

console.log(summary);

Answer 4

经过一番探索之后，我设法提出了一个使用dateformat的解决方案，并允许您轻松自定义日期。这不使用库和直接ES6。如果您运行代码段，则会看到您的日期匹配并存储。

const arr = {  
   post_views:[  
      {  
         id:1,
         post_id:5,
         ip_address:"xxx",
         created_at:"2016-08-08T22:22:45+0000",
         updated_at:"2016-08-08T22:22:45+0000"
      },
      {  
         id:2,
         post_id:5,
         ip_address:"yyy",
         created_at:"2016-08-08T22:23:00+0000",
         updated_at:"2016-08-08T22:23:00+0000"
      },
      {  
         id:3,
         post_id:5,
         ip_address:"yyy",
         created_at:"2016-08-09T22:23:00+0000",
         updated_at:"2016-08-08T22:23:00+0000"
      },
   ]
}
const filterDate = new Date(2016, 08, 08);

function parseDate(date) {
  const dateString = date.split("T")[0].split('-'); //Get just the date portion, and then split that into an array.
  const newDate = new Date(Number(dateString[0]), Number(dateString[1]), Number(dateString[2])) //Make the new date object
  return newDate;
}

let myMatches = arr.post_views.filter(thisDate => parseDate(thisDate.created_at).getTime() == filterDate.getTime());

console.log(myMatches);

给我数组中具有相同日期的所有元素JS

更新

4 个答案: