具有唯一DateTime字符串的数组？

Question

我有Array<object>，它包含类型为n的对象

{
  name: 'random',
  startDate: '2017-11-10 09:00',
  endDate: '2017-11-23 11:00'
}

我想要的是，在呈现结果之前，在新 Array<object中过滤这个数组，它包含startDate (以及它的唯一，2017-11-10 09:00和2017-11-10 10:00并不是统一的)和一个counter，这个Date在数据数组中的次数是多少次。我怎样才能做到这一点？

Answer 1

您可以首先像这样使用Array.prototype.reduce()：

​

const dates = [{
    name: 'random',
    startDate: '2017-11-10 09:00',
    endDate: '2017-11-23 11:00'
  },
  {
    name: 'random',
    startDate: '2017-11-10 09:00',
    endDate: '2017-11-23 11:00'
  },
  {
    name: 'random',
    startDate: '2017-11-10 09:00',
    endDate: '2017-11-23 11:00'
  },
  {
    name: 'random',
    startDate: '2017-08-12 09:00',
    endDate: '2017-11-23 11:00'
  }
];

const hash = dates.reduce((a, c) => (a[c.startDate] = ++a[c.startDate] || 1, a), {});
const uniqueDates = Object.keys(hash).map(k => ({ startDate: k, counter: hash[k] }));

console.log(uniqueDates);

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​

Answer 2

​

var dateList = [{
  name: 'foo',
  startDate: '2017-11-10 09:00',
  endDate: '2017-11-23 11:00'
}, {
  name: 'bar',
  startDate: '2017-11-10 09:01',
  endDate: '2017-11-23 11:00'
}, {
  name: 'baz',
  startDate: '2017-11-10 09:00',
  endDate: '2017-11-24 10:00'
}, {
  name: 'biz',
  startDate: '2017-11-10 09:01',
  endDate: '2017-11-25 09:00'
}, {
  name: 'quick',
  startDate: '2017-11-10 09:00',
  endDate: '2017-11-23 11:00'
}, {
  name: 'brown',
  startDate: '2017-12-10 09:00',
  endDate: '2017-11-23 11:00'
}, {
  name: 'fox',
  startDate: '2017-12-10 10:00',
  endDate: '2017-11-23 11:00'
}];


var startDateCountList = dateList.reduce(function (collector, dateItem) {
  var
    startDate = dateItem.startDate,
    dateCount = collector.registry[startDate];

  if (!dateCount) {
    dateCount = collector.registry[startDate] = {
      startDate : dateItem.startDate,
      count     : 0
    };
    collector.list.push(dateCount);
  }
  dateCount.count += 1;

  return collector;

}, {

  registry: {},
  list:     []

}).list;


console.log('startDateCountList : ', startDateCountList);

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​