Ndtyjky

I have two configurations (json) for particles js. One of them is for winter time, so it should be active from 21. December to 21. March. I tried many things, and still not working (Not because is still November :) )
Last thing I tried is this

var today = new Date();

var tDate = today.getDate();

var tMonth = today.getMonth();



var startingDate = new Date();

var sDate = startingDate.setDate(1);

var sMonth = startingDate.setMonth(10);



var endingDate = new Date();

var eDate = endingDate.setDate(21);

var eMonth = endingDate.setMonth(2);



if (tMonth >= sMonth && tMonth <= eMonth) {

    if (tDate >= sDate && tDate <= eDate) {

        particlesJS.load('particles', '../../Content/Scripts/particles/particles-config-winter.json');

    }

}

else {

    particlesJS.load('particles', '../../Content/Scripts/particles/particles-config.json');

}

This does not make sense, because starting and ending date is both 21. I tried to compare as string, didn't work out. I have no ideas how to compare two dates in javascript. Any help?

You could use this function:

function isWinter(dt) {

    const m = dt.getMonth();

    return m == 11 ? dt.getDate() >= 21 : m == 2 ? dt.getDate() < 21 : m < 2;

}

Call it for today's date like this:

if (isWinter(new Date())) {  /*....*/ }

One of the issues in your attempt is that setMonth and setDate methods return the modified date as number of milliseconds (not just a month or day part) and mutate the date on which the method is called.

Explanation of the function:

The ternary expression uses this logic:

• If the month is December (11), then return true when the day-of-the-month is at least 21 or false otherwise: this is what dt.getDate() >= 21 evaluates to (true or false).


• Otherwise, if the month is March (2), then return true when the day-of-the-month is less than 21 or false otherwise: same principle as above, but reversed


• Otherwise, return true when the month comes before March ( < 2 ) and false otherwise: this is what m < 2 evaluates to.

Date manipulation is always a struggle. If you don't mind libraries to handle this for you, i would suggest you to look at MomentJs which makes it easy to manipulate date and time. However each library you add, you add unnecessary code which you might not need. Therefore if you only need do a few date manipulations, it might not be worth it and trincot's's answer is perfect, if you don't really need MomentJs.

Following the line of trincot's answer, this is how you do the same thing in MomentJs:

function isWinter(date){

  date.year(moment().year()); //Normalize year.

  let winterStart = moment('21-12', 'DD-MM');

  let winterEnd = moment('21-03', 'DD-MM');

  return !date.isBetween(winterEnd, winterStart, 'day')

}

//Tests:

let today = moment('20-12', 'DD-MM');

alert(isWinter(today)); //false

today = moment('21-12', 'DD-MM');

alert(isWinter(today)); //true

today = moment('21-03', 'DD-MM');

alert(isWinter(today)); //true

today = moment('22-03', 'DD-MM');

alert(isWinter(today)); //false

today = moment('22-03-2019', 'DD-MM-YYYY');

alert(isWinter(today)); //false

today = moment('21-03-2019', 'DD-MM-YYYY');

alert(isWinter(today)); //true

<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.22.2/moment.min.js"></script>

To explain why your code doesn't work:

var today = new Date();

var tDate = today.getDate();

var tMonth = today.getMonth();



var startingDate = new Date();



// This sets the date to the first of the month, and sets sDate to a number

// that is the time value of the adjusted date

var sDate = startingDate.setDate(1);



// This sets the month to November and sMonth to the adjusted time value

var sMonth = startingDate.setMonth(10);



var endingDate = new Date();



// As above, this sets endingDate to 21 March and sets eDate and eMonth to numbers

var eDate = endingDate.setDate(21);

var eMonth = endingDate.setMonth(2);



// This will never be true after 1970-01-01 as you're comparing a months to a time values

if (tMonth >= sMonth && tMonth <= eMonth) {

  if (tDate >= sDate && tDate <= eDate) {

Even if this used correct values, the logic doesn't work as even for a date in the range, you're then comparing the date (day number) when that should only be compared if the month is March or November, not any other month (per Trincot's answer).

It's easier if you create dates for 21 March and 21 December in the current year, then see if the current date falls in the range. If it does, it's not winter. If it doesn't, it's winter. I've assumed that the range is inclusive, adjust the dates if that isn't the case.

function isWinter(date = new Date()) {

  var start = new Date(date.getFullYear(), 2, 21);

  var end = new Date(date.getFullYear(), 11, 21);

  return date > start && date < end;

}



[new Date(2018, 0, 1), //  1 Jan 2018, winter

 new Date(2018, 2,21), // 21 Mar 2018, winter

 new Date(2018, 5, 1), //  1 Jun 2018, not winter

 new Date(2018,11,21), // 21 Dec 2018, winter

 new Date()            // Today ...

].forEach(d => console.log(`${d} is ${isWinter(d)?'not ':''}winter`));