How to validate user input date is the last day of the month using javascript?

For brevity you can return ( thisValue == thatValue ); for a boolean result.

I think your code is based on 1970 where it should be relative to the current year to cater for the 29th of February in leap years.

Thanks
can you suggest a better approach ?

//Try something like this:

You can do it like this...

Just add one day to the given date, then if the date goes to a different month, then it is last day.

function isLastDate(date){
var givenDate = new Date(date);
var nextDayDate = new Date(date);
nextDayDate.setDate(givenDate.getDate() + 1);
return !(nextDayDate.getMonth() == givenDate.getMonth());
}

alert(isLastDate('2008/2/29'));

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@cmalakar - No, the solution requires last day of a given month, not just any month.

@Proculopsis, still that should work for a given month too..

When user selects a month and date, form a date string (with a known year), then pass it to my function.

Thanks a lot
I just need to pass the Month to the function and then it will calculate the last day of that month and will compare it with what the user has input .
1)  so one solution is instead of passing both a user selected date and a month , only a month can be passed and then the last day for that month can be calculated and compared to the user entered date
@Proculopsis: as per sur solution

function isLastDayOfMonth( date, month ) {
  return ( date.toString() == new Date( date.getFullYear(), month, 0, 0, 0, 0, 0 ).toString() );
}

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i just need to pass the month so how will ur function work ?
2) solution is as suggested by cmalakar to check whether the date entered by the user is the last day
@cmalakar
How will your function behave if i have to calculate the last  business day of the month ?

Thanks a lot for your time and suggestions

>>I just need to pass the Month to the function and then it will calculate the last day of that month

Then use the below function.

give month values as jan - 1, feb - 2, march - 3, etc.

function getLastDayOfMonth(month){
var firstDayDate = new Date(new Date().getFullYear(), (month), 0, 0, 0, 0, 0);
return firstDayDate.getDate();
}
alert(getLastDayOfMonth(4));

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>>How will your function behave if i have to calculate the last  business day of the month

What you mean by last business day, last friday of the month ?

@cmalakar
User entered month would be stored in
var month = getMonthFromUserInput();

and then I can pass that mnth to

function getLastDayOfMonth(month){
var firstDayDate = new Date(new Date().getFullYear(), (month), 0, 0, 0, 0, 0);
return firstDayDate.getDate();
}

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I will have to assign values to each month and then pass the values to the function instead .

so what you have suggested seems a better approach as I just have to check for that date only :)
butu what if the last business day is the last friday of the month for that country e.g US
and also I need to know the US holidays also

If you want to get the date of last Friday of the given month, then use below.

function getLastFridayDateOfMonth(month){
var firstDayDate = new Date(new Date().getFullYear(), (month), 0, 0, 0, 0, 0);
var lastDay = firstDayDate.getDay();
var daysToReduce = 0;
if(lastDay < 5){
 daysToReduce = lastDay + 2;
}
if(lastDay == 6){
  daysToReduce = 1;
}
firstDayDate.setDate(firstDayDate.getDate() - daysToReduce);
return firstDayDate.getDate(); 
}
alert(getLastFridayDateOfMonth(12));

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>>also I need to know the US holidays also

There is no automatic way of doing this.. you should hard code this in your code.

function LastDayVal(effectiveAsOfDateDay){
	alert("Inside LastDayVal");
	var inputDate = effectiveAsOfDateDay;
	alert("Inputdate is" + inputDate); 
	var nextDateDay = effectiveAsOfDateDay;
	alart("nextDateDay is " + nextDateDay)
	nextDateDay.setDate(inputDate.getDate() +1 );
	alert("NextDateDay is " + nextDateDay);
	return !(nextDayDate.getMonth() == inputDate.getMonth());
	  
}

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while running the code
it doesnt print alart("nextDateDay is " + nextDateDay)

There may be some error in javascript code.

Check javascript console. Press Ctrl+Shift+J in Firefox

var userEnteredDate ;
var userEnteredMonth ;
then
var effectiveAsOfDateYear = document.forms[0].effectiveAsOfDateYear.value;
var effectiveAsOfDateMonth = document.forms[0].effectiveAsOfDateMonth.value;
var effectiveAsOfDateDay = document.forms[0].effectiveAsOfDateDay.value;

userEnteredDate = effectiveAsOfDateDay;
userEnteredMonth = effectiveAsOfDateMonth;
function LastDayVal(effectiveAsOfDateMonth,effectiveAsOfDateDay ){
        alert ("effectiveAsOfDateMonth is " + effectiveAsOfDateMonth);
       alert("effectiveAsOfDateDay is " + effectiveAsOfDateDay);      
      var lastDayDate = new Date ((new Date(effectiveAsOfDateMonth,1)) -1 ) ;
      alert ("lastDay is " + lastDayDate);
      return (lastDayDate == effectiveAsOfDateDay )
 }
While running above code
im passing the effectiveAsOfDateMonth as 7,effectiveAsOfDateDay as 24
while im printing inside the LastDayVal function
the value of effectiveAsOfDateMonth  comes as 6
and the value effectiveAsOfDateDay  comes as 24
and the value of lastDayDate  comes as Wed Jan 31 23:59:59 UTC +530 1906

var effectiveAsOfDateYear = document.forms[0].effectiveAsOfDateYear.value;
var effectiveAsOfDateMonth = document.forms[0].effectiveAsOfDateMonth.value;
 var effectiveAsOfDateDay = document.forms[0].effectiveAsOfDateDay.value;            userEnteredDate = effectiveAsOfDateDay; 
 userEnteredMonth = effectiveAsOfDateMonth;   
  // **Then using if condition**  
  if (!isLastDayOfMonth(userEnteredDate, userEnteredMonth))   { 
    alert("Inside isLastDayOfMonth of continueUploadReportAction "); 
   // Do something   
      }   
  ------------------------------------------------------------------ 
// The function is defined as below **strong text**          
   function isLastDayOfMonth( date, month ) {
           alert("Inside isLastDayOfMonth , the date is " + date ); 
       alert("Inside isLastDayOfMonth , the month is " + month );  
  return ( date.toString() == new Date( date.getFullYear(), month, 0, 0, 0, 0, 0 ).toString() );  
           } 

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However while runtime the when I select the month as 7 and date as 24
then actual values passed to the isLastDayOfMonth function are alert("Inside isLastDayOfMonth ,
the date is " + date ); is 6 and alert("Inside isLastDayOfMonth , the month is " + month ); is 24 and return never seems to be correct