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Trying to compute number of days for a given month

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Apr 12.2005

I know I’m probably missing something obvious, but I can’t see why this doesn’t work…..

// Constructor
function calendar(id, d){
this.id = id;
this.dateObject = d;
this.write = writeCalendar;
this.month = d.getMonth();
this.date = d.getDate();
this.day = d.getDay();
this.year = d.getFullYear();
[B]this.length = getLength();[/B]

this.getFormattedDate = getFormattedDate;
d.setDate(1);
this.firstDay = d.getDay();
d.setDate(this.date);
}

[B]function getLength()[/B]{
switch(this.month){
case 1:
if ((this.dateObject.getFullYear()%4==0 &&
this.dateObject.getFullYear()%100!=0) ||
this.dateObject.getFullYear()%400==0)
return 29; // leap year
else
return 28;
case 3:
return 30;
case 5:
return 30;
case 8:
return 30;
case 10:
return 30;
default:
return 31;
}
}

My getLength function is returning 31 for April and I can’t figure out why this doesn’t work. 0 = Jan, so 3 should = April….Can anyone tell me what I’m doing wrong here ??? Thanks. ?

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JavaScript

10 Comments(s) ↴

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@liezicaApr 12.2005 — Have you tried to alert (this.month)? Does it give you what you expect it to be (3 for april I assume) Apparently that is where your problem must be;

Or maybe you should call the function like this:

this.length = getLength(this.month);

function getLength(this.month){...

I can't see any other problems.
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@snyder2005authorApr 12.2005 — Yes, I did add an alert to display the month just prior to calling the getLength function and it displays '3'. I'll try calling the function the way you suggested and see if that makes a difference. Thanks for your help !
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@Orc_ScorcherApr 12.2005 — The way you're calling getLength, |this| will not be bound to your date object.

Change this line

this.length = getLength();

to

this.length = getLength.call(this);

And a shorter way to get the number of days in a month:function getLength() {
var _
return (_ = new Date(this), _.setDate(32), 32 - _.getDate())
}
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@A1ien51Apr 12.2005 — I personally would do this to find the number of days in the month. No calculations of leap year required with this method...

<i>
</i>&lt;script type="text/javascript"&gt;

Date.prototype.DaysCount = function(){
var dateNew = new Date((this.getMonth()+2) + "/0/" + this.getFullYear());
return dateNew.getDate();
}

var today = new Date();

var numDays = today.DaysCount();
alert("There are " + numDays + " days!");

&lt;/script&gt;


Eric
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@snyder2005authorApr 12.2005 — Thanks ORC SCORCHER, changing the call to getLength, worked great ! I tried your suggestion, for a more elegant way of computing the number of days in month, but the getLength function returns 'NaN'.... Can you see something I'm doing wrong ?

function calendar(id, d){

this.id = id;

this.dateObject = d;

this.write = writeCalendar;

this.month = d.getMonth();

this.date = d.getDate();

this.day = d.getDay();

this.year = d.getFullYear();

this.length = getLength.call(this);

alert(this.length);

this.getFormattedDate = getFormattedDate;

this.getFormattedDate2 = getFormattedDate2;

// get the first day of the month's day

d.setDate(1);

this.firstDay = d.getDay();

// then reset the date object to the correct date

d.setDate(this.date);

}

function getLength(){

var nbrDays;

return(nbrDays = new Date(this), nbrDays.setDate(32), 32 - nbrDays.getDate())

}
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@snyder2005authorApr 12.2005 — Thanks for the suggestion, Alien 51, I'll try to incorporate this. I always like to reduce lines of code.
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@Orc_ScorcherApr 12.2005 — The problem is my function requires the date object, not the calendar object as its |this|, so you'd have to call it as getLength.call(d) or getLength.call(this.dateObject)
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@snyder2005authorApr 12.2005 — Duh....I'm blind, thanks for all your help....works great now !
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@CharlesApr 12.2005 — &lt;script type="text/javascript"&gt;
&lt;!--
Date.prototype.getDaysInMonth = function() {return new Date (this.getFullYear(), this.getMonth() + 1, 0).getDate()}

alert (new Date().getDaysInMonth())
// --&gt;
&lt;/script&gt;
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@CharlesApr 12.2005 — &lt;script type="text/javascript"&gt;
&lt;!--
Date.getDaysInMonth = function(year, monthIndex) {return new Date (year, monthIndex + 1, 0).getDate()}

alert (Date.getDaysInMonth(2005, 0))
// --&gt;
&lt;/script&gt;
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