Question

I’ve written a jQuery function to check the total number of characters in a given textbox and pop up a warning if it exceeds the maximum (user-defined) length.

Example: (greatly simplified):

function checkLength(txt)
{
   if (txt.length >= maxlength) 
   {
      alert('Too much text entered');
      return false;
   }
   else
      return true;
}

This works as expected, but like a good little developer I also perform server-side validation against the length of the field the entered text is assigned to (on my domain object).

It’s there that I noticed that the following string:

12<RETURN>34 

(where <RETURN> is obviously the return character)

will return 5 as length in Javascript
and return 6 as length in .NET (String.Length)

Am I missing something here? Or will I be forced to count the number of returns in the javascript string and then double them to get the ‘correct’ .NET count? Any pointers on how to handle this?

UPDATE: I can indeed get the correct length by doing the replace as suggested below.

function GetCurrentLength(txt) {
   return txt.replace(/\n/g, "\n\r").length;
}

However, there is more to the question than detecting the character count, because once the system detects that too much characters have been entered, it should (client-side) strip all excess characters away (this can be more than one, because the users might copy-paste too much text into the textbox).

Something like:

if (textLength > maxlength) {
    self.val(text.substr(0, maxlength));
}

This of course will get me into trouble if I count returns double, because the wrong number of characters risk being deleted. How can I reliably delete the right number of characters then?

Answer 1

This was my final solution, feels a bit dirty, but does the job.

// Calculate the length of a string, but take care to count returns for 2 characters instead 
        // of one. That way, we should get the same length as in .NET

        function GetCurrentLength(txt) {
            return txt.length + GetNumberOfReturns(txt);
        }

        function GetNumberOfReturns(txt)
        {
            var numberOfReturns = 0
            var enterRegExpr = txt.match(/\n/g);
            if (enterRegExpr)
                numberOfReturns = enterRegExpr.length ;

            return numberOfReturns;
        }

        function CutToMaxLength(txt, maxlength) {
            return txt.substr(0, maxlength - GetNumberOfReturns(txt));
        }