Compare dates with loop and javascript

Question

I need to compare dates with javascript so I write a function:

function fulljson (){
    var db_data;
    $.ajax({
                url: "http://localhost:8888/auction/offers/5", 
                type: "GET",
                async: true, 
                dataType: "html",
                success: function(data) {
                var db_data = $.parseJSON(data);
                console.log(db_data);

    // declare variables
    var period_start = new Date('2016-02-24'),
        period_now = new Date();
        period_end = new Date('2016-11-01'),
        //current_date = period_start,
        array_of_all_dates = [];
console.log(period_start);
        var dodaj = parseInt('3');
        period_now = period_now.setDate(period_now.getDate() + dodaj);

        console.log(new Date(period_start).getTime() + ' i ' + period_now);

        if (new Date(period_start).getTime() > period_now){
            current_date = new Date(period_start);

        } else {
            current_date = new Date(period_now);
            current_date.setHours(1
                ,0,0,0);
        }

        //current_date = moment(current_date).format('YYYY-MM-DD');
        console.log(current_date);
    // Create a populated array of dates
   // Create a populated array of dates
    while (current_date.getTime() <= period_end.getTime()) {
      array_of_all_dates.push(current_date);
      current_date = new Date(+current_date);
      current_date.setDate(current_date.getDate() + 1);
    }

    // Now loop over the array of populated dates and mutate, so something like
    array_of_all_dates = array_of_all_dates.map(function (date) {
      var found_in_db = db_data.filter(function (db_data) {
        return new Date(db_data.start).getTime() === date.getTime(); // You need to do this comparison better!
      });
      if (found_in_db.length > 0) {
        return found_in_db[0];
      }
      var new_object = {
        title: '',
        start: date,
        price: '60'
      };
      console.log(new_object);
      return new_object;

    });



    console.log('result'+array_of_all_dates);
    drawCalendar(array_of_all_dates);
                }, 
                error: function (data) {
                console.log(data);
                console.log('GRESKA NEKA');
                }      
    });
        //end OF AJAX

};

My ajax function gets this data:

[{"id":82,"price":61,"start":"Mon, 28 Mar 2016 00:00:00 +0000"},{"id":81,"price":61.5,"start":"Sun, 27 Mar 2016 00:00:00 +0000"},{"id":79,"price":61,"start":"Sun, 13 Mar 2016 00:00:00 +0000"},{"id":72,"price":61,"start":"Tue, 29 Mar 2016 00:00:00 +0000"},{"id":66,"price":61,"start":"Sat, 12 Mar 2016 00:00:00 +0000"},{"id":64,"price":60.5,"start":"Fri, 11 Mar 2016 00:00:00 +0000"}]

Now my function which needs to compare dates works only in this case to 27. March 2016.

Also my period_start is 24. Feb. and period_end is 1.Nov.2016.

Why my function work only to 27.March?

Is this some PHP templating system? new Date('{{ date('Y-m-d', strtotime($article->from)) }}')? JS has no strtotime() or date() function — Marc B
– Marc B, Commented Feb 10, 2016 at 20:10
show the actual generated JS, then. not this js/php mishmash. — Marc B
– Marc B, Commented Feb 10, 2016 at 20:11
you really should evaluate that code again. why are you doing *THREE new Date(period_start) in a row? why create the same object three times, especially since you don't change the date value... — Marc B
– Marc B, Commented Feb 10, 2016 at 20:15

RobG · Accepted Answer · 2016-02-12 03:46:12Z

1

This is a comment, but there's not enough space and I'd like to format it.

In the code:

var period_start = new Date('2016-02-24'),
        period_now = new Date();  // <=== terminates statement
        period_end = new Date('2016-11-01'),
        //current_date = period_start,
        array_of_all_dates = [];

Note that the second line is terminated with a semicolon, so period_end and array_of_all_dates become global. This likely isn't an issue, but who knows…

Also, the current interpretation of ECMAScript 2015 is that:

new Date('2016-02-24')

should create a new Date for 2016-02-24T00:00:00Z, i.e. it is treated as UTC (which is inconsistent with ISO 8601 and the standard itself since a date and time string without a timezone like 2016-02-24T00:00:00 is treated as local, but remove the time part and it's UTC).

Next,

new Date()

creates a local* date, so if today is 2016-02-12 then:

new Date() != new Date('2016-02-12')

for all time zones with an offset other than 00:00 since the time values will differ by the timezone offset.

It's not clear to me whether the above has a serious affect on your code or not, but freely mixing UTC and local dates is not a good idea.

Next, I don't understand the use of:

var dodaj = parseInt('3');

rather than:

var dodaj = 3;

And:

if (new Date(period_start).getTime() > period_now)

creates and discards a Date object for no reason, the following is exactly equivalent:

if (period_start > period_now)

with the benefit that it avoids an obscure bug in IE regarding new Date(date) and two digit years.

Oh, lastly, 27 March 2016 is a Sunday when daylight saving starts in many places (e.g. Italy, though not the US), so perhaps daylight saving is messing with your dates?

* where "local date" means a Date with a time value adjusted for the current timezone offset settings of the host.

edited Feb 12, 2016 at 3:46

answered Feb 12, 2016 at 3:34

RobG

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4 Comments

MonkeyBusiness Over a year ago

I solve my problem with: return new Date(db_data.start).toDateString() === date.toDateString();

RobG Over a year ago

@MonkeyBusiness—it would make more sense to use return +new Date(db_data.start) == +date so that you compare the time values directly.

MonkeyBusiness Over a year ago

Can you please write full example and we can test?

RobG Over a year ago

@MonkeyBusiness—once there is sufficient information to do so. Are the dates to be treated as local or UTC?

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