Min/Max of dates in an array?_问答_开发者_运维开发者技术经验分享

How can I find out the min and the max date from an array of dates? Currently, I am creating an array like this:

var dates = [];
dates.push(new Date("2011/06/25"))
dates.push(new Date("2011/06/26"))
dates.push(new Date("2011/06/27"))
dates.push(new Date("2011/06/28"))

Is there a built-in function to do this or am I to write my开发者_如何学编程 own?

Code is tested with IE,FF,Chrome and works properly:

var dates=[];
dates.push(new Date("2011/06/25"))
dates.push(new Date("2011/06/26"))
dates.push(new Date("2011/06/27"))
dates.push(new Date("2011/06/28"))
var maxDate=new Date(Math.max.apply(null,dates));
var minDate=new Date(Math.min.apply(null,dates));

Something like:

var min = dates.reduce(function (a, b) { return a < b ? a : b; }); 
var max = dates.reduce(function (a, b) { return a > b ? a : b; });

Tested on Chrome 15.0.854.0 dev

Same as apply, now with spread :

const maxDate = new Date(Math.max(...dates));

(could be a comment on best answer)

_.min and _.max work on arrays of dates; use those if you're using Lodash or Underscore, and consider using Lodash (which provides many utility functions like these) if you're not already.

For example,

_.min([
    new Date('2015-05-08T00:07:19Z'),
    new Date('2015-04-08T00:07:19Z'),
    new Date('2015-06-08T00:07:19Z')
])

will return the second date in the array (because it is the earliest).

Since dates are converted to UNIX epoch (numbers), you can use Math.max/min to find those:

var maxDate = Math.max.apply(null, dates)
// convert back to date object
maxDate = new Date(maxDate)

(tested in chrome only, but should work in most browsers)

**Use Spread Operators| ES6 **

let datesVar = [ 2017-10-26T03:37:10.876Z,
  2017-10-27T03:37:10.876Z,
  2017-10-23T03:37:10.876Z,
  2015-10-23T03:37:10.876Z ]

Math.min(...datesVar);

That will give the minimum date from the array.

Its shorthand Math.min.apply(null, ArrayOfdates);

ONELINER:

var min= dates.sort((a,b)=>a-b)[0], max= dates.slice(-1)[0];

result in variables min and max, complexity O(nlogn), editable example here. If your array has no-date values (like null) first clean it by dates=dates.filter(d=> d instanceof Date);.

var dates = [];
dates.push(new Date("2011-06-25")); // I change "/" to "-" in "2011/06/25"
dates.push(new Date("2011-06-26")); // because conosle log write dates 
dates.push(new Date("2011-06-27")); // using "-".
dates.push(new Date("2011-06-28"));

var min= dates.sort((a,b)=>a-b)[0], max= dates.slice(-1)[0];

console.log({min,max});

var max_date = dates.sort(function(d1, d2){
    return d2-d1;
})[0];

if you get max or min date with string type from string date of array,you can try this:

const dates = ["2021-02-05", "2021-05-20", "2021-01-02"]
const min = dates.reduce((acc,date)=>{return acc&&new Date(acc)<new Date(date)?acc:date},'')
const max = dates.reduce((acc,date)=>{return acc&&new Date(acc)>new Date(date)?acc:date},'')

The above answers do not handle blank/undefined values to fix this I used the below code and replaced blanks with NA :

function getMax(dateArray, filler) {
      filler= filler?filler:"";
      if (!dateArray.length) {
        return filler;
      }
      var max = "";
      dateArray.forEach(function(date) {
        if (date) {
          var d = new Date(date);
          if (max && d.valueOf()>max.valueOf()) {
            max = d;
          } else if (!max) {
            max = d;
          }
        }
      });
      return max;
    };
console.log(getMax([],"NA"));
console.log(getMax(datesArray,"NA"));
console.log(getMax(datesArray));

function getMin(dateArray, filler) {
 filler = filler ? filler : "";
  if (!dateArray.length) {
    return filler;
  }
  var min = "";
  dateArray.forEach(function(date) {
    if (date) {
      var d = new Date(date);
      if (min && d.valueOf() < min.valueOf()) {
        min = d;
      } else if (!min) {
        min = d;
      }
    }
  });
  return min;
}

console.log(getMin([], "NA"));
console.log(getMin(datesArray, "NA"));
console.log(getMin(datesArray));

I have added a plain javascript demo here and used it as a filter with AngularJS in this codepen

This is a particularly great way to do this (you can get max of an array of objects using one of the object properties): Math.max.apply(Math,array.map(function(o){return o.y;}))

This is the accepted answer for this page: Finding the max value of an attribute in an array of objects

Using only one loop in typescript you can get min/max date values at the same time:

function minMaxDates(dates: Date[]): {minDate: Date, maxDate: Date} {
    let minDate = new Date(275760, 8, 13);
    let maxDate = new Date(1970, 1, 1);
    dates.map(date => {
        minDate = minDate < date ? minDate : date;
        maxDate = maxDate > date ? maxDate : date;
    });
    return {minDate, maxDate}
};

To call this function:

const {minDate, maxDate} = minMaxDates(dates);

I posted a demo here.

You can also use date-fns max function if you already have it in your stack:

    import { max } from 'date-fns';
    
    const dates = [
      new Date('2022-01-01'),
      new Date('2023-03-24'),
      new Date('2021-12-31')
    ];
    
    const maxDate = max(...dates);
    
    console.log(maxDate); // Output: Wed Mar 24 2023 00:00:00 GMT-0400 (Eastern Daylight Time)

https://date-fns.org/v2.29.3/docs/max

Using Moment, Underscore and jQuery, to iterate an array of dates.

Sample JSON:

"workerList": [{        
        "shift_start_dttm": "13/06/2017 20:21",
        "shift_end_dttm": "13/06/2017 23:59"
    }, {
        "shift_start_dttm": "03/04/2018 00:00",
        "shift_end_dttm": "03/05/2018 00:00"        
    }]

Javascript:

function getMinStartDttm(workerList) {  
    if(!_.isEmpty(workerList)) {
        var startDtArr = [];
        $.each(d.workerList, function(index,value) {                
            startDtArr.push(moment(value.shift_start_dttm.trim(), 'DD/MM/YYYY HH:mm')); 
         });            
         var startDt = _.min(startDtArr);           
         return start.format('DD/MM/YYYY HH:mm');
    } else {
        return '';
    }   
}

Hope it helps.