how to calculate number of occurrence of character in string using jquery

You can use the below code to find the number of time a character "." occurs in a string.

    var regex = new RegExp(/\./g)
    var count = "This is some text .".match(regex).length;

Your regex needs to be changed. "." in regex means everything. You need to escape the ".". Probably like this...

$(this).val().match(/\./g);

You can try this:

$('.txt').keyup(function() {
   var str = this.value;
   var a = str.split('.');
   if (a.length > 2) {
      this.value = a.slice(0, 2).join('.');//removes 2nd dot and the string following it
      //a[0] +='.'; this.value = a.join('');//only removes redundant dots (alternative)
   }
});

Number of occurences here is a.length-1.

jsfiddle

try below javascript functinon on onkeypress or onkeyup event of a tex box

and call like this onkeypress = "return (event,'txtid',9,2)" beforelength is before '.' how many number allowed and afterLength is for after '.' number length

function isNumberKey(event, obj, beforeLength, afterLength) {
    var keyCode1 = event.keyCode;

    var keyCode = 0;
    if (keyCode1 == 0)
        keyCode = event.which;
    else {
        keyCode = keyCode1;
    }

    //    alert(keyCode);
    //    alert(keyCode1);

    if ((keyCode >= 48 && keyCode <= 57) || keyCode == 46 || keyCode == 13 || keyCode == 27 || keyCode == 127) {
        var text = document.getElementById(obj).value;
        if (keyCode == 46 && keyCode1 == 0) {
            if (text.toString().indexOf(".") != -1) {
                return false;
            }
        }
        if (keyCode == 46) {
            if (text.toString().indexOf(".") != -1) {
                return false;
            }
        }

        //        if (!/^\d{0,10}(?:\.\d{0,2})?$/.test(text)) {
        //            return false;
        //        } else {
        //        }
        var splitText = text.split('.');
        if (splitText[0].length >= beforeLength) {
            if (keyCode == 46 && text.toString().indexOf(".") == -1) {
                return true;
            } else if (text.toString().indexOf(".") != -1) {
                return true;
            }
            return false;
        }
        //        if (splitText.length > 1 && splitText[1].length == afterLength) {
        //            return false;
        //        }
    }
    else {
        return GetDefault(event);
    }
    return true;
}

function GetDefault(event) {
    var keyCode = event.keyCode;
    if (keyCode == 0)
        keyCode = event.which;

    if (keyCode == 8 || keyCode == 9 || keyCode == 35 || keyCode == 36 || keyCode == 37 || keyCode == 38 || keyCode == 39 || keyCode == 40 || keyCode == 46 || keyCode == 118) {
        return true;
    }
    return false;
}

If you are trying to alert user(or other advanced stuff) and that's why you need the count then you need to add length:

$('.txt').keyup(function() {
    var ele = $(this).val();
    var i = ele.indexOf('.');
    if (i > -1) {
        var c = ele.match(/\./g).length);
        // ...
    }
});

If you are just trying to delete the dots then you can use:

$('.txt').keyup(function() {
    $(this).val($(this).val().replace('.', ''));
});

This is what you want exactly..:) Demo here

Escape the character and just count it.

Javascript:

 $('.txt').keyup(function() {
            var ele = $(this).val();

                            alert(ele.match(/\./g).length);

        });

HTML

<textarea id="txt"></textarea>

I have found my way....

var count = 0;
$('.txt').blur(function () 
{
   var t = $(this).val();
   if (t.indexOf('.') >= 0) 
   {
      var j = t.split('.');
      count = j.length - 1;                    
   }
   else 
   {
      count = -1;
   }
}