javascript - What is the elegant way to get the latest date from array of objects in client side? - Stack Overflow

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I use angularjs in project.

I get array of objects from the server. Each object contains few properties and one of them is date property.

Here is the Array (in json) that I get from server:

[
  {
    "Address": 25,
    "AlertType": 1,
    "Area": "North",
    "MeasureDate": "2019-02-01T00:01:01.001Z",
    "MeasureValue": -1
  },
  {
    "Address": 26,
    "AlertType": 1,
    "Area": "West",
    "MeasureDate": "2016-04-12T15:13:11.733Z",
    "MeasureValue": -1
  },
  {
    "Address": 25,
    "AlertType": 1,
    "Area": "North",
    "MeasureDate": "2017-02-01T00:01:01.001Z",
    "MeasureValue": -1
  }
          .
          .
          .
]

I need to get the latest date from the array.

What is the elegant way to get the latest date from array of objects?

I use angularjs in project.

I get array of objects from the server. Each object contains few properties and one of them is date property.

Here is the Array (in json) that I get from server:

[
  {
    "Address": 25,
    "AlertType": 1,
    "Area": "North",
    "MeasureDate": "2019-02-01T00:01:01.001Z",
    "MeasureValue": -1
  },
  {
    "Address": 26,
    "AlertType": 1,
    "Area": "West",
    "MeasureDate": "2016-04-12T15:13:11.733Z",
    "MeasureValue": -1
  },
  {
    "Address": 25,
    "AlertType": 1,
    "Area": "North",
    "MeasureDate": "2017-02-01T00:01:01.001Z",
    "MeasureValue": -1
  }
          .
          .
          .
]

I need to get the latest date from the array.

What is the elegant way to get the latest date from array of objects?

• javascript
• jquery
• angularjs

Share Improve this question Follow edited Apr 12, 2016 at 16:12 Astaroth 78366 silver badges2525 bronze badges asked Apr 12, 2016 at 15:05 MichaelMichael 13.6k5959 gold badges169169 silver badges313313 bronze badges 5

• 1 Loop over and find the latest date. – epascarello Commented Apr 12, 2016 at 15:08
• @epascarello, do i have to convert it to Date javascript object. – Michael Commented Apr 12, 2016 at 15:25
• Yes you would need to convert the string to a date. – epascarello Commented Apr 12, 2016 at 15:29
• You don't need to convert it. It can be ordered as is. And, in fact, there are some arguments to say introducing conversion opens the floor for introducing more potential areas for issues to appear (parsing etc.). – user1017882 Commented Apr 12, 2016 at 16:24
• You don't have to convert it because of the specific format you have chosen. I'd argue that it's better to convert though, since if your application ever uses a different format or accepts multiple formats then this could break whereas parsing as a date and then ordering ensures that it truly is the latest date (which may not necessarily be the last ordered string). For example, if you start accepting MM/DD/YYYY dates, then string order could be drastically different from date order. – arcyqwerty Commented Apr 12, 2016 at 19:10

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12 Answers 12

Sorted by: Reset to default 156

A clean way to do it would be to convert each date to a Date() and take the max

ES6:

new Date(Math.max(...a.map(e => new Date(e.MeasureDate))));

JS:

new Date(Math.max.apply(null, a.map(function(e) {
  return new Date(e.MeasureDate);
})));

where a is the array of objects.

What this does is map each of the objects in the array to a date created with the value of MeasureDate. This mapped array is then applied to the Math.max function to get the latest date and the result is converted to a date.

By mapping the string dates to JS Date objects, you end up using a solution like Min/Max of dates in an array?

--

A less clean solution would be to simply map the objects to the value of MeasureDate and sort the array of strings. This only works because of the particular date format you are using.

a.map(function(e) { return e.MeasureDate; }).sort().reverse()[0]

If performance is a concern, you may want to reduce the array to get the maximum instead of using sort and reverse.

Further to @Travis Heeter's answer, this returns the object that contains the latest date:

array.reduce((a, b) => (a.MeasureDate > b.MeasureDate ? a : b));

A more robust solution perhaps might be convert the strings into Date objects every time. Could be noticeably slower if dealing with (very) large arrays:

array.reduce((a, b) => {
  return new Date(a.MeasureDate) > new Date(b.MeasureDate) ? a : b;
});

If you want to get the whole Object, not just the date...

If OP's array of Objects was assigned to a this is how you get the Object with the most recent date:

var mostRecentDate = new Date(Math.max.apply(null, a.map( e => {
   return new Date(e.MeasureDate);
})));
var mostRecentObject = a.filter( e => { 
    var d = new Date( e.MeasureDate ); 
    return d.getTime() == mostRecentDate.getTime();
})[0];

1. a.map gets the dates from the array of objects.
2. new Date is applied to each date, making Date Objects
3. Math.max.apply finds the most recent
4. We have found the most recent Date, now we need the object.
5. a.filter loops through the original a array.
6. We need some way to compare dates, so we use .getTime(), which returns the number of milliseconds since 01/01/1970. This will account for time - if it's defined - as well as date.
7. When the correct date is found, true is returned, and .filter gives us just that object.

Note: This solution is an extension of @archyqwerty's answer above. Their solution gave only the most recent date from an array of objects, this solution gives you the whole Object that the date was a member of.

Modification to Anton Harald's answer: The array I have uses ModDate instead of MeasureDate. I am choosing the most recent date. This works.

  getLatestDate(xs) {
   if (xs.length) {
   return xs.reduce((m,v,i) => (v.ModDate > m.ModDate) && i ? v : m).ModDate;
  }
}

m = accumulator, v = current , i = index

Environment: TypeScript, ES6

Answers rated by performance:

1. data.reduce((a, b) => a.MeasureDate > b.MeasureDate ? a : b).MeasureDate
2. data.map(e => e.MeasureDate).reduce((a, b) => a > b ? a : b)
3. new Date(Math.max.apply(null, data.map(e => new Date(e.MeasureDate)))).toISOString()

(assuming x is the array)

function getLatestDate(data) {
   // convert to timestamp and sort
   var sorted_ms = data.map(function(item) {
      return new Date(item.MeasureDate).getTime()
   }).sort(); 
   // take latest
   var latest_ms = sorted_ms[sorted_ms.length-1];
   // convert to js date object 
   return new Date(latest_ms);
}

var data = [{MeasureDate: "2014-10-04T16:10:00"},
            {MeasureDate: "2013-10-04T16:10:00"},
            {MeasureDate: "2012-10-04T16:10:00"}];

getLatestDate(data).toString(); // "Sat Oct 04 2014 18:10:00 GMT+0200 (CEST)"

This function returns the latest date as a JavaScript date Object. You can also turn it into an ISO-String (the format of your source data) with the Date-Object method toISOString().

var date_str = "2012-10-04T16:10:00";
(new Date(date_str)).toISOString(); // "2012-10-04T16:10:00.000Z"

As you can see the result of the method includes always zero milliseconds in the end. If you need your original ISO data-string as a result, you may want to go with the following function:

function getLatestDate2(data) {

   var sorted = data.map(function(item) {
      var MeasureDate = item.MeasureDate;
      return {original_str: MeasureDate,
              in_ms: (new Date(MeasureDate)).getTime()}
   }).sort(function(item1, item2) {
      return (item1.in_ms < item2.in_ms)
   }); 

   // take latest
   var latest = sorted[0];

   return latest.original_str;
}

getLatestDate2(data); // "2014-10-04T16:10:00"

Also further to @TravisHeeter's answer..

Instead of using 'filter' and grabbing the array index of [0], you can use the .find() method instead as follows:

....

const mostRecentObject = a.find( e => { 
    const d = new Date( e.MeasureDate ); 
    return d.getTime() == mostRecentDate.getTime();
});

This also makes the code more performant, as it will stop looking after it has found the result, rather than filter which will iterate over all objects in the array.

By this, you can get the whole object - I just clubbed the process which I learned from Travis Heeter's answer:

let latestDate = Math.max(...a.map((ele) => new Date(ele.dof)));
latestDate = new Date(latestDate);
console.log(latestDate);

let latestObject = a.filter((ele) => {
  let date = new Date(ele.dof);
  return date.getTime() === latestDate.getTime();
});

Inspired by many of the suggestions and comments in this thread, here is another solution for the problem. It's very fast, since there is no date object convertion.

function getLatestDate(xs) {
   if (xs.length) {
      return xs.reduce((m, i) => (i.MeasureDate > m) && i || m, "")
               .MeasureDate;
   }
 }

Here's a version for Browser's not supporting arrow functions:

function getLatestDateSave(xs) {
   if (xs.length) {
      return xs.reduce(function(m, i) {
         return (i.MeasureDate > m) && i || m;
      }, "").MeasureDate;
   }
 }

This how I picked lasest/highest date

var maxLastseen= obj.sort((a,b) => new Date(b.lastS).getTime() - new Date(a.lastS).getTime())[0];

If you need to get the latest date in string format, following a similar approach to @Yorkshireman and adding an initial value ('') as suggested by @Nikhil Nanjappa in the comments:

array.reduce(
  (acc, element) => {
      const { MeasureDate } = element

      // Accumulator is empty string, return MeasureDate, accumulator is now MeasureDate
      if (!acc) return MeasureDate

      return new Date(MeasureDate) > new Date(acc) ? MeasureDate : acc
  },
  ''
)

        var dates = []; 

        dates.push(new Date("2019/06/25")); 
        dates.push(new Date("2019/06/26")); 
        dates.push(new Date("2019/06/27")); 
        dates.push(new Date("2019/06/28")); 

        function GFG_Fun() { 
            var maximumDate=new Date(Math.max.apply(null, dates)); 
            var minimumDate=new Date(Math.min.apply(null, dates)); 
        } 

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