Develop Reference

Only 4 digit numbers in input field in MVC TextBoxFor

I have an MVC5 project and I have an input field that I only want to take an 8 digit number. I tried implementing it like this:
#Html.TextBoxFor(model => model.oldPin, new { maxlength = "8", #class = "form-control disablecopypaste", onkeydown = "return isNumber(event);" })
function isNumber(evt) {
evt = (evt) ? evt : window.event;
var charCode = (evt.which) ? evt.which : evt.keyCode;
if (charCode === 16) {
return false;
}
if (charCode > 31 && (charCode < 48 || charCode > 57)) {
return false;
}
return true;
}
My problem is that while this prevents numbers it allows spaces and special characters. How do I prevent this? It works with the keypress event but its depreciated and I'm concerned about browser compatibility. Is there any way to do this with the keydown event? All the answers I've seen are all with the keypress event.

function allowNumberOnly (e) {
var ascii = (e.which) ? e.which : e.keyCode
if (ascii> 31 && (ascii< 48 || ascii> 57)) {
return false;
}
else {
var vall = $('#oldPin').val()
if (vall.length > 3) {
return false;
}
else {
return true;
}
}
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<input class="form-control " id="oldPin" name="oldPin" onkeypress="return allowNumberOnly(event)" type="text" value="">

How to automatically add a dot after the nth character automatically in textarea?

I have to write a textarea in which the user should enter the given latitude in decimal degrees.
For example: 60.45678 or 05.1
What should I do to make a dot appear in the textarea automatically after the second character?
I already have a function to check if the characters are numbers:
<script language=Javascript>
function isNumberKey(evt) {
var charCode = (evt.which) ? evt.which : event.keyCode
if (charCode > 31 && (charCode < 48 || charCode > 57))
return false;
return true;
} </script>
Maybe it can be somehow modified so that it would add a dot and check if the first two numbers are smaller than 90?
<textarea name="LongitudeEW" placeholder="Longitude East/West." onkeypress="return isNumberKey(event)"></textarea>
Thanks for the help :)

Try this
var DECIMAL_REGEXP = /(?<=^.{2}$)/g;
function handleKeyUp(e) {
var target = e.target;
var charCode = e.which || e.keyCode;
if(charCode > 31 && (charCode < 48 || charCode > 57)){
return false;
}
target.value = target.value.replace(DECIMAL_REGEXP, '.');
return true;
}
var DECIMAL_REGEXP = /(?<=^.{2}$)/g;
function handleKeyUp(e) {
var target = e.target;
var charCode = e.which || e.keyCode;
if(charCode > 31 && (charCode < 48 || charCode > 57)){
return false;
}
target.value = target.value.replace(DECIMAL_REGEXP, '.');
return true;
}
<textarea name="LongitudeEW" placeholder="Longitude East/West." onkeypress="return handleKeyUp(event)"></textarea>
In case you want to bind to the elements keypress event vs inlining:
// cache the regexp
var DECIMAL_REGEXP = /(?<=^.{2}$)/g;
// ref the textarea
var textrea = document.getElementById('LongitudeEW');
// bind to the keypress event
textrea.addEventListener('keypress', function(e){
var target = e.target,
charCode = e.which || e.keyCode;
if(charCode > 31 && (charCode < 48 || charCode > 57)){
e.preventDefault();
}
target.value = target.value.replace(DECIMAL_REGEXP, '.');
});
<textarea id="LongitudeEW" name="LongitudeEW" placeholder="Longitude East/West."></textarea>

You can try using this library: https://nosir.github.io/cleave.js/
For example as your requirement. Hope to help, my friend :))
<script src="cleave.js"></script>
<input class="input-element" type="textarea" >
<script>
$(function(){
var cleave = new Cleave('.input-element', {
delimiter: '.',
blocks: [2, 100],
numericOnly: true
});
});
</script>

Cross Browser issue with Keyup Validation

<script type="text/javascript">
function numbersonly(e){
var unicode=e.charCode? e.charCode : e.keyCode
if (unicode!=8){ //if the key isn't the backspace key (which we should allow)
if (unicode<65||unicode>90) //if not a Capital Alphabet
return false //disable key press
}
}
</script>
<form>
<input type="text" size=18 onkeyup="return numbersonly(event)">
</form>
This code is working fine. But IE doesn't support charcode. and In Keycode, 65 to 90 range includes both capital and lower case letters. How to resolve the issue?

It will not handled by the simple one you have to check many conditions in that case like,
Checking caps lock on or not
Use this function for this,
function isCapslock(e){
e = (e) ? e : window.event;
var charCode = false;
if (e.which) {
charCode = e.which;
} else if (e.keyCode) {
charCode = e.keyCode;
}
var shifton = false;
if (e.shiftKey) {
shifton = e.shiftKey;
} else if (e.modifiers) {
shifton = !!(e.modifiers & 4);
}
if (charCode >= 97 && charCode <= 122 && shifton) {
return true;
}
if (charCode >= 65 && charCode <= 90 && !shifton) {
return true;
}
return false;
}
Refered from http://dougalmatthews.com/articles/2008/jul/2/javascript-detecting-caps-lock/
Additionally
just use e.which in jquery. They normalize this value for all browsers.
Additionally you can check for e.shiftKey.
Source Using e.keyCode || e.which; how to determine the differance between lowercase and uppercase?

JavaScript keycode allow number and plus symbol only

I have this JavaScript function that is used to force user only type number in the textbox. Right now and I want to modify this function so it will allow the user to enter plus (+) symbol. How to achieve this?
//To only enable digit in the user input
function isNumberKey(evt)
{
var charCode = (evt.which) ? evt.which : event.keyCode
if (charCode > 31 && (charCode < 48 || charCode > 57))
return false;
return true;
}

Since the '+' symbol's decimal ASCII code is 43, you can add it to your condition.
for example :
function isNumberKey(evt)
{
var charCode = (evt.which) ? evt.which : event.keyCode
if (charCode != 43 && charCode > 31 && (charCode < 48 || charCode > 57))
return false;
return true;
}
This way, the Plus symbol is allowed.

This code might work. I added support for SHIFT + (equal sign) and the numpad +.
function isNumberKey(evt)
{
var charCode = (evt.which) ? evt.which : event.keyCode;
var shiftPressed = (window.Event) ? e.modifiers & Event.SHIFT_MASK : e.shiftKey;
if ((shiftPressed && charCode == 187) || (charCode == 107))
{
return true;
} else if ((charCode > 95) && (charCode < 106)) {
return true;
} else if (charCode > 31 && (charCode < 48 || charCode > 57))) {
return false;
} else {
return true;
}
}

this is stupid ... not really an answer at all. I would suggest you to do following.
function isNumberKey(evt)
{
console.log(evt.keyCode);
return false;
}
And find out the ranges of all keys, and implement it.

It's Work. Javascript keycode allow number and plus symbol only
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>JavaScript form validation</title>
</head>
<body>
<form name="form1" action="#">
Mobile Number: <input type='text' id='PhoneNumber' maxlength="10" onKeyPress="return IsNumeric3(event);" ondrop="return false;" onpaste="return false;"/>
<span id="error3" style="color: Red; display: none">* Input digits (0 - 9)</span>
</form>
<script type="text/javascript">
var specialKeys = new Array();
specialKeys.push(8);
specialKeys.push(43);
specialKeys.push(37);
specialKeys.push(39);
//Backspace
function IsNumeric3(e) {
var keyCode = e.which ? e.which : e.keyCode
var ret = (keyCode != 37 && keyCode != 8 && keyCode != 46 && (keyCode >= 48 && keyCode <= 57) || specialKeys.indexOf(keyCode) != -1);
document.getElementById("error3").style.display = ret ? "none" : "inline";
return ret;
}
</script>
<script>
function stringlength(inputtxt, minlength, maxlength)
{
var field = inputtxt.value;
var mnlen = minlength;
var mxlen = maxlength;
if(field.length<mnlen || field.length> mxlen)
{
alert("Please input the 10 digit mobile number");
return false;
}
else
{
return true;
}
}
</script>
</body>
</html>
Thank you friends

Here is the modified code:
function isNumberKey(evt)
{
var charCode = (evt.which) ? evt.which : event.keyCode
if ( (charCode >= 48 && charCode <= 57) || charCode == 43)
return true;
return false;
}

Here is the code . working fine with numbers and plus + sign in phone fields. you will have to implement the code on keydown function . target the id/class of the particular phone field and use keydown function.
//allows only these keys
// backspace, delete, tab, escape, and enter
if ( event.keyCode == 107 || event.keyCode == 46 || event.keyCode == 8 || event.keyCode == 9 || event.keyCode == 27 || event.keyCode == 13 ||
// Ctrl+A
(event.keyCode == 65 && event.ctrlKey === true) ||
// home, end, left, right
(event.keyCode >= 35 && event.keyCode <= 39)) {
return;
}
else {
// Ensure that it is a number and stop the keypress
if (event.shiftKey || (event.keyCode < 48 || event.keyCode > 57) && (event.keyCode < 96 || event.keyCode > 105 )) {
event.preventDefault();
}
}

Using experience of my colleagues above, write one function, that fits me well. It filters all except numbers, arrows and backspace. Maybe it would be useful for somebody.
function isKeyCorrect(keyEvent) {
var charCode = keyEvent.which ? keyEvent.which : keyEvent.keyCode;
var isNotNumber = charCode < 48 || charCode > 57;
var isNotArrow = charCode < 37 || charCode > 40;
var isNotBackspace = charCode !== 8;
return isNotNumber && isNotArrow && isNotBackspace;
}

<script type="text/javascript">
$(document).ready(function() {
`enter code here` $('#form-1').submit(function(msg) {
$.post("action.php?act=login",$(this).serialize(),function(data){
if (data == 'ERR:A3001004') { alert("Güvenlik hatası, sayfayı yenileyin."); }
else if (data == 'TIMEEND') { alert("Anahtarınızın süresi dolmuş."); }
else if (data == 'INVALID') { alert("Geçersiz anahtar şifresi girdiniz."); }
else if (data == 'OK') { alert("Başarıyla giriş yaptınız. Yetişkinlere göre içerik barındıran sitelere erişim sağlayabilirsiniz."); }
});
return false;
});
});
function isNumberKey(evt)
{
var charCode = (evt.which) ? evt.which : event.keyCode
if (charCode > 31 && (charCode < 48 || charCode > 57))
return false;
return true;
}
</script>

Restricting input to textbox: allowing only numbers and decimal point

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

<HTML>
<HEAD>
<SCRIPT language=Javascript>
<!--
function isNumberKey(evt)
{
var charCode = (evt.which) ? evt.which : evt.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>
This really works!

The accepted solution is not complete, since you can enter multiple '.', for example 24....22..22. with some small modifications it will work as intended:
<html>
<head>
<script type="text/javascript">
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;
}
</script>
</head>
<body>
<input type="text" onkeypress="return isNumberKey(this, event);" />
</body>
</html>

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.

Here is one more solution which allows for decimal numbers and also limits the digits after decimal to 2 decimal places.
function isNumberKey(evt, element) {
var charCode = (evt.which) ? evt.which : event.keyCode
if (charCode > 31 && (charCode < 48 || charCode > 57) && !(charCode == 46 || charCode == 8))
return false;
else {
var len = $(element).val().length;
var index = $(element).val().indexOf('.');
if (index > 0 && charCode == 46) {
return false;
}
if (index > 0) {
var CharAfterdot = (len + 1) - index;
if (CharAfterdot > 3) {
return false;
}
}
}
return true;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="number" id="rate" placeholder="Billing Rate" required onkeypress="return isNumberKey(event,this)">

All solutions presented here are using single key events. This is very error prone since input can be also given using copy'n'paste or drag'n'drop. Also some of the solutions restrict the usage of non-character keys like ctrl+c, Pos1 etc.
I suggest rather than checking every key press you check whether the result is valid in respect to your expectations.
var validNumber = new RegExp(/^\d*\.?\d*$/);
var lastValid = document.getElementById("test1").value;
function validateNumber(elem) {
if (validNumber.test(elem.value)) {
lastValid = elem.value;
} else {
elem.value = lastValid;
}
}
<textarea id="test1" oninput="validateNumber(this);" ></textarea>
The oninput event is triggered just after something was changed in the text area and before being rendered.
You can extend the RegEx to whatever number format you want to accept. This is far more maintainable and extendible than checking for single key presses.

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>

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

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);">

For anyone stumbling here like I did, here is a jQuery 1.10.2 version I wrote which is working very well for me albeit resource intensive:
/***************************************************
* Only allow numbers and one decimal in text boxes
***************************************************/
$('body').on('keydown keyup keypress change blur focus paste', 'input[type="text"]', function(){
var target = $(this);
var prev_val = target.val();
setTimeout(function(){
var chars = target.val().split("");
var decimal_exist = false;
var remove_char = false;
$.each(chars, function(key, value){
switch(value){
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
case '.':
if(value === '.'){
if(decimal_exist === false){
decimal_exist = true;
}
else{
remove_char = true;
chars[''+key+''] = '';
}
}
break;
default:
remove_char = true;
chars[''+key+''] = '';
break;
}
});
if(prev_val != target.val() && remove_char === true){
target.val(chars.join(''))
}
}, 0);
});

A small correction to #rebisco's brilliant answer to validate the decimal perfectly.
function isNumberKey(evt) {
debugger;
var charCode = (evt.which) ? evt.which : event.keyCode;
if (charCode == 46 && evt.srcElement.value.split('.').length>1) {
return false;
}
if (charCode != 46 && charCode > 31 && (charCode < 48 || charCode > 57))
return false;
return true;
}

If you want it for float values,
Here is the function I am using
<HTML>
<HEAD>
<SCRIPT language=Javascript>
<!--
function check(e, value) {
//Check Charater
var unicode = e.charCode ? e.charCode : e.keyCode;
if (value.indexOf(".") != -1)
if (unicode == 46) return false;
if (unicode != 8)
if ((unicode < 48 || unicode > 57) && unicode != 46) return false;
}
//-->
</SCRIPT>
</HEAD>
<BODY>
<INPUT id="txtChar" onkeypress="return check(event,value)" type="text" name="txtChar">
</BODY>
</HTML>

function onlyDotsAndNumbers(txt, event) {
var charCode = (event.which) ? event.which : event.keyCode
if (charCode == 46) {
if (txt.value.indexOf(".") < 0)
return true;
else
return false;
}
if (txt.value.indexOf(".") > 0) {
var txtlen = txt.value.length;
var dotpos = txt.value.indexOf(".");
//Change the number here to allow more decimal points than 2
if ((txtlen - dotpos) > 2)
return false;
}
if (charCode > 31 && (charCode < 48 || charCode > 57))
return false;
return true;
}
<input type="text" id="txtAmount" onkeypress="return onlyDotsAndNumbers(this,event);" maxlength="10" oncopy="return false" ondrag="return false" ondrop="return false" onpaste="return false" />
Only Numbers, One decimal point, No Copy Paste.

inputelement.onchange= inputelement.onkeyup= function isnumber(e){
e= window.event? e.srcElement: e.target;
while(e.value && parseFloat(e.value)+''!= e.value){
e.value= e.value.slice(0, -1);
}
}

function integerwithdot(s, iid){
var i;
s = s.toString();
for (i = 0; i < s.length; i++){
var c;
if (s.charAt(i) == ".") {
} else {
c = s.charAt(i);
}
if (isNaN(c)) {
c = "";
for(i=0;i<s.length-1;i++){
c += s.charAt(i);
}
document.getElementById(iid).value = c;
return false;
}
}
return true;
}

Suppose your textbox field name is Income
Call this validate method when you need to validate your field:
function validate() {
var currency = document.getElementById("Income").value;
var pattern = /^[1-9]\d*(?:\.\d{0,2})?$/ ;
if (pattern.test(currency)) {
alert("Currency is in valid format");
return true;
}
alert("Currency is not in valid format!Enter in 00.00 format");
return false;
}

Extending the #rebisco's answer. this below code will allow only numbers and single '.'(period) in the text box.
function isNumberKey(evt) {
var charCode = (evt.which) ? evt.which : event.keyCode;
if (charCode != 46 && charCode > 31 && (charCode < 48 || charCode > 57)) {
return false;
} else {
// If the number field already has . then don't allow to enter . again.
if (evt.target.value.search(/\./) > -1 && charCode == 46) {
return false;
}
return true;
}
}

alternative way to restrict input to a text-box so that it accepts only numbers and the decimal point is to
use javascript inside the html input. This works for me:
<input type="text" class="form-control" id="price" name="price" placeholder="Price"
vrequired onkeyup="this.value=this.value.replace(/[^0-9.]/g, '').replace(/(\..*)\./g, '$1')">
--Accepts--
9
9.99
--Do not accept--
9.99.99
ABC

Better solution
var checkfloats = function(event){
var charCode = (event.which) ? event.which : event.keyCode;
if (charCode != 46 && charCode > 31 && (charCode < 48 || charCode > 57))
return false;
if(event.target.value.indexOf('.') >=0 && charCode == 46)
return false;
return true;
}

I chose to tackle this on the oninput event in order to handle the issue for keyboard pasting, mouse pasting and key strokes. Pass true or false to indicate decimal or integer validation.
It's basically three steps in three one liners. If you don't want to truncate the decimals comment the third step. Adjustments for rounding can be made in the third step as well.
// Example Decimal usage;
// <input type="text" oninput="ValidateNumber(this, true);" />
// Example Integer usage:
// <input type="text" oninput="ValidateNumber(this, false);" />
function ValidateNumber(elm, isDecimal) {
try {
// For integers, replace everything except for numbers with blanks.
if (!isDecimal)
elm.value = elm.value.replace(/[^0-9]/g, '');
else {
// 1. For decimals, replace everything except for numbers and periods with blanks.
// 2. Then we'll remove all leading ocurrences (duplicate) periods
// 3. Then we'll chop off anything after two decimal places.
// 1. replace everything except for numbers and periods with blanks.
elm.value = elm.value.replace(/[^0-9.]/g, '');
//2. remove all leading ocurrences (duplicate) periods
elm.value = elm.value.replace(/\.(?=.*\.)/g, '');
// 3. chop off anything after two decimal places.
// In comparison to lengh, our index is behind one count, then we add two for our decimal places.
var decimalIndex = elm.value.indexOf('.');
if (decimalIndex != -1) { elm.value = elm.value.substr(0, decimalIndex + 3); }
}
}
catch (err) {
alert("ValidateNumber " + err);
}
}

Starting from #rebisco answer :
function count_appearance(mainStr, searchFor) {
return (mainStr.split(searchFor).length - 1);
}
function isNumberKey(evt)
{
$return = true;
var charCode = (evt.which) ? evt.which : event.keyCode;
if (charCode != 46 && charCode > 31
&& (charCode < 48 || charCode > 57))
$return = false;
$val = $(evt.originalTarget).val();
if (charCode == 46) {
if (count_appearance($val, '.') > 0) {
$return = false;
}
if ($val.length == 0) {
$return = false;
}
}
return $return;
}
Allows only this format : 123123123[.121213]
Demo here demo

Hope it will work for you.
<input type="text" onkeypress="return chkNumeric(event)" />
<script>
function chkNumeric(evt) {
evt = (evt) ? evt : window.event;
var charCode = (evt.which) ? evt.which : evt.keyCode;
if (charCode > 31 && (charCode < 48 || charCode > 57)) {
if (charCode == 46) { return true; }
else { return false; }
}
return true;
}
</script>

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;
}

I observed that for all the answers provided here, the things are not working if we select some portion of the text in textbox and try to overwrite that part.
So I modified the function which is as below:
<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;
}
if (charCode == 46 && evt.srcElement.value.split('.').length>1 )
{
return false;
}
if(evt.srcElement.selectionStart<evt.srcElement.selectionEnd)
{
return true;
}
if(evt.srcElement.value.split('.').length>1 && evt.srcElement.value.split('.')[1].length==2)
{
return false;
}
return true;
}
//-->
</SCRIPT>
</HEAD>
<BODY>
<INPUT id="txtChar" onkeypress="return isNumberKey(event)"
type="text" name="txtChar">
</BODY>
</HTML>

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;
}

<input type="text" class="number_only" />
<script>
$(document).ready(function() {
$('.number_only').keypress(function (event) {
return isNumber(event, this)
});
});
function isNumber(evt, element) {
var charCode = (evt.which) ? evt.which : event.keyCode
if ((charCode != 45 || $(element).val().indexOf('-') != -1) && (charCode != 46 || $(element).val().indexOf('.') != -1) && ((charCode < 48 && charCode != 8) || charCode > 57)){
return false;
}
else {
return true;
}
}
</script>
http://www.encodedna.com/2013/05/enter-only-numbers-using-jquery.htm

function isNumberKey(evt)
{
var charCode = (evt.which) ? evt.which : evt.keyCode;
if(charCode==8 || charCode==13|| charCode==99|| charCode==118 || charCode==46)
{
return true;
}
if (charCode > 31 && (charCode < 48 || charCode > 57))
{
return false;
}
return true;
}
It will allow only numeric and will let you put "." for decimal.

<script type="text/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>
#Html.EditorFor(model => model.Orderids, new { id = "Orderids", Onkeypress=isNumberKey(event)})
This works fine.

Best and working solution with Pure-Javascript sample
Live demo : https://jsfiddle.net/manoj2010/ygkpa89o/
<script>
function removeCommas(nStr) {
if (nStr == null || nStr == "")
return "";
return nStr.toString().replace(/,/g, "");
}
function NumbersOnly(myfield, e, dec,neg)
{
if (isNaN(removeCommas(myfield.value)) && myfield.value != "-") {
return false;
}
var allowNegativeNumber = neg || false;
var key;
var keychar;
if (window.event)
key = window.event.keyCode;
else if (e)
key = e.which;
else
return true;
keychar = String.fromCharCode(key);
var srcEl = e.srcElement ? e.srcElement : e.target;
// control keys
if ((key == null) || (key == 0) || (key == 8) ||
(key == 9) || (key == 13) || (key == 27))
return true;
// numbers
else if ((("0123456789").indexOf(keychar) > -1))
return true;
// decimal point jump
else if (dec && (keychar == ".")) {
//myfield.form.elements[dec].focus();
return srcEl.value.indexOf(".") == -1;
}
//allow negative numbers
else if (allowNegativeNumber && (keychar == "-")) {
return (srcEl.value.length == 0 || srcEl.value == "0.00")
}
else
return false;
}
</script>
<input name="txtDiscountSum" type="text" onKeyPress="return NumbersOnly(this, event,true)" />

Working on the issue myself, and that's what I've got so far. This more or less works, but it's impossible to add minus afterwards due to the new value check. Also doesn't allow comma as a thousand separator, only decimal.
It's not perfect, but might give some ideas.
app.directive('isNumber', function () {
return function (scope, elem, attrs) {
elem.bind('keypress', function (evt) {
var keyCode = (evt.which) ? evt.which : event.keyCode;
var testValue = (elem[0].value + String.fromCharCode(keyCode) + "0").replace(/ /g, ""); //check ignores spaces
var regex = /^\-?\d+((\.|\,)\d+)?$/;
var allowedChars = [8,9,13,27,32,37,39,44,45, 46] //control keys and separators
//allows numbers, separators and controll keys and rejects others
if ((keyCode > 47 && keyCode < 58) || allowedChars.indexOf(keyCode) >= 0) {
//test the string with regex, decline if doesn't fit
if (elem[0].value != "" && !regex.test(testValue)) {
event.preventDefault();
return false;
}
return true;
}
event.preventDefault();
return false;
});
};
});
Allows:
11 11 .245 (in controller formatted on blur to 1111.245)
11,44
-123.123
-1 014
0123 (formatted on blur to 123)
doesn't allow:
!##$/*
abc
11.11.1
11,11.1
.42

<input type="text" onkeypress="return isNumberKey(event,this)">
<script>
function isNumberKey(evt, obj) {
var charCode = (evt.which) ? evt.which : event.keyCode
var value = obj.value;
var dotcontains = value.indexOf(".") != -1;
if (dotcontains)
if (charCode == 46) return false;
if (charCode == 46) return true;
if (charCode > 31 && (charCode < 48 || charCode > 57))
return false;
return true;
}
</script>