Date Parsing and Validation in JavaScript

Question

How would I achieve the pseudo-code below in JavaScript? I want to include the date check in the second code excerpt, where txtDate is for the BilledDate.

If ABS(billeddate – getdate)  >  31 then yesno “The date you have entered is more than a month from today, Are you sure the date is correct,”.


if (txtDate && txtDate.value == "")
{
    txtDate.focus();
    alert("Please enter a date in the 'Date' field.")
    return false;
}

Answer 1

Hello and good day for everyone

You can try Refular Expressions to parse and validate a date format

here is an URL yoy can watch some samples and how to use

http://www.javascriptkit.com/jsref/regexp.shtml

A very very simple pattern would be: \d{2}/\d{2}/\d{4}

for MM/dd/yyyy or dd/MM/yyyy

With no more.... bye bye

Answer 2

Generally speaking you work with Date-objects in javascript, and these should be constructed with the following syntax:

    var myDate = new Date(yearno, monthno-1, dayno);
    //you could put hour, minute, second and milliseconds in this too

Beware, the month-part is an index, so january is 0, february is 1 and december is 11 !-)

Then you can pull out anything you want, the .getTime() thing returns number of milliseconds since start of Unix-age, 1/1 1970 00:00, så this value you could subtract and then look if that value is greater than what you want:

//today (right now !-) can be constructed by an empty constructor
var today = new Date();
var olddate = new Date(2008,9,2);
var diff = today.getTime() - olddate.getTime();
var diffInDays = diff/(1000*60*60*24);//24 hours of 60 minutes of 60 second of 1000 milliseconds

alert(diffInDays);

This will return a decimal number, so probably you'll want to look at the integer-value:

alert(Math.floor(diffInDays));

Answer 3

To get the date difference in days in plain JavaScript, you can do it like this:

var billeddate = Date.parse("2008/10/27");
var getdate = Date.parse("2008/09/25");

var differenceInDays = (billeddate - getdate)/(1000*60*60*24)

However if you want to get more control in your date manipulation I suggest you to use a date library, I like DateJS, it's really good to parse and manipulate dates in many formats, and it's really syntactic sugar:

// What date is next thrusday?
Date.today().next().thursday();
//or
Date.parse('next thursday');

// Add 3 days to Today
Date.today().add(3).days();

// Is today Friday?
Date.today().is().friday();

// Number fun
(3).days().ago();

Answer 4

You can use this to check for valid date

function IsDate(testValue) {

        var returnValue = false;
        var testDate;
        try {
            testDate = new Date(testValue);
            if (!isNaN(testDate)) {
                returnValue = true;            
            }
            else {
                returnValue = false;
            }
        }
        catch (e) {
            returnValue = false;
        }
        return returnValue;
    }

And this is how you can manipulate JS dates. You basically create a date object of now (getDate), add 31 days and compare it to the date entered

function IsMoreThan31Days(dateToTest) {

  if(IsDate(futureDate)) {
      var futureDateObj = new Date();
      var enteredDateObj = new Date(dateToTest);

      futureDateObj.setDate(futureDateObj.getDate() + 31); //sets to 31 days from now.
      //adds hours and minutes to dateToTest so that the test for 31 days is more accurate.
      enteredDateObj.setHours(futureDateObj.getHours()); 
      enteredDateObj.setMinutes(futureDateObj.getMinutes() + 1);

      if(enteredDateObj >= futureDateObj) {
        return true;
      }
      else {
        return false;
      }
   }
}