Is there an array containing unique DateTime strings?

I am dealing with an Array<object> containing n objects of a specific type.

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

My goal is to filter this array before rendering the results into a new Array<object which only includes the unique values of the startDate field (e.g., 2017-11-10 09:00 and 2017-11-10 10:00 are not unique) along with a counter indicating how many times each unique date appears in the data array. How can I accomplish this task?

javascripttypescript

Answer №1

var dateEntries = [{
  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 startDateOccurrences = dateEntries.reduce(function (tempCollector, date) {
  var
    startDateStr = date.startDate,
    count = tempCollector.directory[startDateStr];

  if (!count) {
    count = tempCollector.directory[startDateStr] = {
      startDate : date.startDate,
      occurrence     : 0
    };
    tempCollector.list.push(count);
  }
  count.occurrence += 1;

  return tempCollector;

}, {

  directory: {},
  list:     []

}).list;


console.log('startDateOccurrences : ', startDateOccurrences);
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Answer №2

To start, you can utilize the Array.prototype.reduce() method in the following manner:

const dates = [{
    name: 'example',
    startDate: '2018-05-20 10:00',
    endDate: '2018-05-21 15:00'
  },
  {
    name: 'example',
    startDate: '2018-05-22 09:00',
    endDate: '2018-05-23 11:30'
  },
  {
    name: 'example',
    startDate: '2018-06-01 08:00',
    endDate: '2018-06-02 18:00'
  },
  {
    name: 'example',
    startDate: '2018-05-20 10:00',
    endDate: '2018-05-21 15:00'
  }
];

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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