how to calculate values of an (javascript) object with date keys

Question

I have the following simplified (javascript) object, of which properties are dates (in string fomat):

Given a random startdate and enddate within the range of dates in the object, how to code (efficiently) the calculation - say accumulate- of the values within this range? As an example, for the following code the calculation result should be 12 (3+4+5) for the given startdate and enddate.

var startdate = '2014-01-03';
var enddate = '2014-01-05'
var obj = {};
obj['2014-01-02'] = '2';
obj['2014-01-03'] = '3';
obj['2014-01-04'] = '4';
obj['2014-01-05'] = '5';
obj['2014-01-06'] = '6';

Arrays cannot have strings as keys in javascript. Maybe you meant to use an object? `{}` — qwertynl, Jan 28 '14 at 14:32
@user2543182 Your code is still invalid. `var obj = {}` is used to create objects not `[]`. — dee-see, Jan 28 '14 at 14:38

Robin Giltner · Accepted Answer · 2014-01-29T13:54:43.957

0

You can just loop through the properties of the object, doing a comparison, and adding.

var startdate = '2014-01-04';
var enddate = '2014-01-05';
var arr = {};
arr['2014-01-02'] = '2';
arr['2014-01-03'] = '3';
arr['2014-01-04'] = '4';
arr['2014-01-05'] = '5';
arr['2014-01-06'] = '6';

var total = 0;
for(var p in arr) {
  if(arr.hasOwnProperty(p)) {
      if(new Date(p) >= new Date(startdate) && new Date(p) <= new Date(enddate)) {
        total += parseInt(arr[p], 10);
      }
   }
}

console.log(total);

Sample http://jsbin.com/imUdewaJ/1/edit

I'm sure there is a better way to do this, but I don't know how due to having to parse the date object out for comparison.

--Edit added in the hasOwnProperty check from comments below

edited Jan 29 '14 at 13:54

answered Jan 28 '14 at 14:41

Robin Giltner

3,057
2
18
26

I would cache start and end date `Date` objects so that you do not have to keep computing them – qwertynl Jan 28 '14 at 14:54
when using `for (x in y)` use `hasOwnProperty'. See [this question](http://stackoverflow.com/questions/12735778/for-in-and-hasownproperty). – R. Oosterholt Jan 28 '14 at 14:56
@Oosterholt: good tip too. In my case the object only has one property however... – Joppo Jan 28 '14 at 15:15

score 0 · Answer 2 · edited May 23 '17 at 11:56

0

It's possible that some browsers won't support date1 > date2, so it might be better to also use getTime().

function getDate(date) {
  return new Date(date).getTime();
}

function getTotal(start, end) {
  var total = 0;
  for (var k in obj) {
    var current = getDate(k);
    if (current >= start && current <= end) {
      total += parseInt(obj[k], 10);
    }
  }
  return total;
}

var start = getDate(startdate);
var end = getDate(enddate);

console.log(getTotal(start, end)); // 12

edited May 23 '17 at 11:56

Community

1
1

answered Jan 28 '14 at 14:52

Andy

61,948
13
68
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when using `for (x in y)` use `hasOwnProperty'. See [this question](http://stackoverflow.com/questions/12735778/for-in-and-hasownproperty). – R. Oosterholt Jan 28 '14 at 14:55
No need in this case. – Andy Jan 28 '14 at 16:09

score 0 · Answer 3 · edited Jan 28 '14 at 16:06

When doing stuff with dates, you might want to use thirdparty tools to handle browser compatibility. Momentjs is a good one for dates.

solution with momentjs:

var startdate = moment('2014-01-03');
var enddate = moment('2014-01-05');

var obj = {};
obj['2014-01-02'] = '2';
obj['2014-01-03'] = '3';
obj['2014-01-04'] = '4';
obj['2014-01-05'] = '5';
obj['2014-01-06'] = '6';

var strDate;
var total = 0;
for (strDate in obj) {
    if (obj.hasOwnProperty(strDate)) {
        var date = moment(strDate)
        if (date.diff(startdate, 'days')>=0 && date.diff(enddate, 'days')<=0) {
            total += parseInt(obj[strDate], 10);
        }
    }
}

console.log(total);

how to calculate values of an (javascript) object with date keys

3 Answers3