Restricting input to textbox: allowing only number

Question

How can I restrict input to a text-box so that it accepts only numbers and the decimal point?

Answer 1

Just need to apply this method in Jquery and you can validate your textbox to just accept number with a decimal only.

function IsFloatOnly(element) {    
var value = $(element).val(); 
var regExp ="^\\d+(\\.\\d+)?$";
return value.match(regExp); 
}

Please see working demo here

Answer 2

here is script that cas help you :

<script type="text/javascript">
// price text-box allow numeric and allow 2 decimal points only
function extractNumber(obj, decimalPlaces, allowNegative)
{
    var temp = obj.value;

    // avoid changing things if already formatted correctly
    var reg0Str = '[0-9]*';
    if (decimalPlaces > 0) {
        reg0Str += '\[\,\.]?[0-9]{0,' + decimalPlaces + '}';
    } else if (decimalPlaces < 0) {
        reg0Str += '\[\,\.]?[0-9]*';
    }
    reg0Str = allowNegative ? '^-?' + reg0Str : '^' + reg0Str;
    reg0Str = reg0Str + '$';
    var reg0 = new RegExp(reg0Str);
    if (reg0.test(temp)) return true;

    // first replace all non numbers
    var reg1Str = '[^0-9' + (decimalPlaces != 0 ? '.' : '') + (decimalPlaces != 0 ? ',' : '') + (allowNegative ? '-' : '') + ']';
    var reg1 = new RegExp(reg1Str, 'g');
    temp = temp.replace(reg1, '');

    if (allowNegative) {
        // replace extra negative
        var hasNegative = temp.length > 0 && temp.charAt(0) == '-';
        var reg2 = /-/g;
        temp = temp.replace(reg2, '');
        if (hasNegative) temp = '-' + temp;
    }

    if (decimalPlaces != 0) {
        var reg3 = /[\,\.]/g;
        var reg3Array = reg3.exec(temp);
        if (reg3Array != null) {
            // keep only first occurrence of .
            //  and the number of places specified by decimalPlaces or the entire string if decimalPlaces < 0
            var reg3Right = temp.substring(reg3Array.index + reg3Array[0].length);
            reg3Right = reg3Right.replace(reg3, '');
            reg3Right = decimalPlaces > 0 ? reg3Right.substring(0, decimalPlaces) : reg3Right;
            temp = temp.substring(0,reg3Array.index) + '.' + reg3Right;
        }
    }

    obj.value = temp;
}
function blockNonNumbers(obj, e, allowDecimal, allowNegative)
{
    var key;
    var isCtrl = false;
    var keychar;
    var reg;
    if(window.event) {
        key = e.keyCode;
        isCtrl = window.event.ctrlKey
    }
    else if(e.which) {
        key = e.which;
        isCtrl = e.ctrlKey;
    }

    if (isNaN(key)) return true;

    keychar = String.fromCharCode(key);

    // check for backspace or delete, or if Ctrl was pressed
    if (key == 8 || isCtrl)
    {
        return true;
    }

    reg = /\d/;
    var isFirstN = allowNegative ? keychar == '-' && obj.value.indexOf('-') == -1 : false;
    var isFirstD = allowDecimal ? keychar == '.' && obj.value.indexOf('.') == -1 : false;
    var isFirstC = allowDecimal ? keychar == ',' && obj.value.indexOf(',') == -1 : false;
    return isFirstN || isFirstD || isFirstC || reg.test(keychar);
}
function blockInvalid(obj)
{
    var temp=obj.value;
    if(temp=="-")
    {
        temp="";
    }

    if (temp.indexOf(".")==temp.length-1 && temp.indexOf(".")!=-1)
    {
        temp=temp+"00";
    }
    if (temp.indexOf(".")==0)
    {
        temp="0"+temp;
    }
    if (temp.indexOf(".")==1 && temp.indexOf("-")==0)
    {
        temp=temp.replace("-","-0") ;
    }
    if (temp.indexOf(",")==temp.length-1 && temp.indexOf(",")!=-1)
    {
        temp=temp+"00";
    }
    if (temp.indexOf(",")==0)
    {
        temp="0"+temp;
    }
    if (temp.indexOf(",")==1 && temp.indexOf("-")==0)
    {
        temp=temp.replace("-","-0") ;
    }
    temp=temp.replace(",",".") ;
    obj.value=temp;
}
// end of price text-box allow numeric and allow 2 decimal points only
</script>

<input type="Text" id="id" value="" onblur="extractNumber(this,2,true);blockInvalid(this);" onkeyup="extractNumber(this,2,true);" onkeypress="return blockNonNumbers(this, event, true, true);">

Answer 3

Following code worked for me

The input box with "onkeypress" event as follows

<input type="text" onkeypress="return isNumberKey(this,event);" />

The function "isNumberKey" is as follows

function isNumberKey(txt, evt) {
  var charCode = (evt.which) ? evt.which : evt.keyCode;
  if (charCode == 46) {
    //Check if the text already contains the . character
    if (txt.value.indexOf('.') === -1) {
        return true;
    } else {
        return false;
    }
  } else {
    if (charCode > 31 && (charCode < 48 || charCode > 57))
        return false;
  }
  return true;
}

Answer 4

Are you looking for something like this?

   <HTML>
   <HEAD>
   <SCRIPT language=Javascript>
      <!--
      function isNumberKey(evt)
      {
         var charCode = (evt.which) ? evt.which : event.keyCode
         if (charCode != 46 && charCode > 31 && (charCode < 48 || charCode > 57))
            return false;

         return true;
      }
      //-->
   </SCRIPT>
   </HEAD>
   <BODY>
      <INPUT id="txtChar" onkeypress="return isNumberKey(event)" type="text" name="txtChar">
   </BODY>
  </HTML>

Answer 5

form.onsubmit = function(){
    return textarea.value.match(/^\d+(\.\d+)?$/);
}

Is this what you're looking for?

I hope it helps.

EDIT: I edited my example above so that there can only be one period, preceded by at least one digit and followed by at least one digit.

Answer 6

For Decimal numbers and also allowing Negatives numbers with 2 places for decimals after the point... I modified the function to:

<input type="text" id="txtSample" onkeypress="return isNumberKey(event,this)"/>



function isNumberKey(evt, element){

        var charCode = (evt.which) ? evt.which : event.keyCode
        if (charCode > 31 && (charCode < 48 || charCode > 57) && !(charCode == 46 || charCode == 8 || charCode == 45))
            return false;
        else {
            var len = $(element).val().length;

            // Validation Point
            var index = $(element).val().indexOf('.');
            if ((index > 0 && charCode == 46) || len == 0 && charCode == 46) {
                return false;
            }
            if (index > 0) {
                var CharAfterdot = (len + 1) - index;
                if (CharAfterdot > 3) {
                    return false;
                }
            }

            // Validating Negative sign
            index = $(element).val().indexOf('-');
            if ((index > 0 && charCode == 45) || (len > 0 && charCode == 45)) {
                return false;
            }
        }
        return true;
    }