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jQuery allow selected characters only keypress function

Hi I tried to use this code to limit user's input. A problem is I cannot use my return key or the enter in my keyboard in the input box. How can I solve my problem.
Im using this code:
$("input").keypress( function(e) {
var chr = String.fromCharCode(e.which);
if ("bcdegkmnqupvxy36789".indexOf(chr) < 0)
return false;
});

To achieve what you need you can simply add another condition to the if statement which checks for the Return keycode: 13:
$("input").keypress(function(e) {
var chr = String.fromCharCode(e.which);
if ("bcdegkmnqupvxy36789".indexOf(chr) < 0 && e.which != 13)
return false;
console.log('allowed');
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="text" name="foo" />

Just update your if condition to allow e.which === 13 (which is the Enter key) as follows:
$("input").keypress( function(e) {
var chr = String.fromCharCode(e.which);
if ("bcdegkmnqupvxy36789".indexOf(chr) < 0 && e.which !== 13) {
return false;
}
console.log( e.which, chr, 'allowed' );
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input />

You only want to limit the input if the user has entered a character and not hit one of the non-character entering keys (like tab, of return/enter).
So check to see if chr is not false-y (e.g. an empty string) first:
$("input").keypress( function(e) {
var chr = String.fromCharCode(e.which);
//if chr is a non-character keycode (like 13) then you won't return false
if (chr && "bcdegkmnqupvxy36789".indexOf(chr) < 0)
return false;
});

$("input").keypress( function(e) {
var chr = String.fromCharCode(e.which);
if ("bcdegkmnqupvxy36789".indexOf(chr) < 0 && e.which !=13 && e.which !=8)
return false;
});

KeyPress and keyup in javascript

I want to allow only numbers and decimal in a inputtext field.
If I use my code in a keypress event it works fine(return false when alphabets are entered), but when i use it with keyup it is not.
My code:
function OnKeyPress(e,DivID) {
if ( e.which != 8 && e.which != 0 && e.which != 13 && e.which != 190 && (e.which < 48 || e.which > 57)) {
return false;
// event.preventDefault();
}
var val = j$('[id$='+DivID+']').val();
if(DivID == 'ProximityCPPercentage')
{
var x = event.which || event.keyCode;
if(val.indexOf('.') >= 0 && e.which == 46)
return false;
else if(e.which == 46 && val.length == 3)
return false;
if(val.indexOf('.') == 0)
val = '0' + val;
if(e.which != 46)
{
strval = val + String.fromCharCode(x);
var re = /^((.|0|[1-9]\d?)(\.\d{1})?|100(\.0?)?)$/;
if(!re.test(strval))
return false;
}
}
else if(val.indexOf('.') >= 0)
{
var reg =/^(\d{0,4}\.?(\d{0,1})|\d{0,6})?$/gm;
if(!reg.test(val))
{
j$('[id$='+DivID+']').val(val.substring(0, val.length - 1));
}
}
else if(e.which != 190 )
{
if(val.length > 5)
return false;
}
}
If I use this function in onkeypress attribute of input field it is not allowing alphabets but when i use in onkeyup it does allows the alphabets.

Ok, I created a simple fiddle with an explanation of what is happening for you https://jsfiddle.net/gb0kwom0/3/
On key down, will capture the event before a value is set in the input (result: alert fire then nothing in input value), see this example.
<input type="text" onkeypress="return onPress()">
<script>
function onPress(){alert(); return false;}
</script>
On key up, will capture the event after a value is set in the input (result: value set then alert will fire), see this example.
<input type="text" onkeyup="return onUp()">
<script>
function onUp(){alert(); return false;}
</script>
So to solve your issue onKeyUp you will need to reset the value.
The result will be: will capture the event after a value is set in the input then reset the value back to empty, see this example.
note: this example is just to show the difference and should not be used, it will reset the whole value back to nothing
<input type="text" onkeyup="onUp2(this)">
<script>
function onUp2(obj){alert(); obj.value='';}
</script>
this method is not ideal and will take a lot more code to get working, it is why you should continue to use onkeypress instead

best way to restrict special characters in text field input [duplicate]

How do I block special characters from being typed into an input field with jquery?

A simple example using a regular expression which you could change to allow/disallow whatever you like.
$('input').on('keypress', function (event) {
var regex = new RegExp("^[a-zA-Z0-9]+$");
var key = String.fromCharCode(!event.charCode ? event.which : event.charCode);
if (!regex.test(key)) {
event.preventDefault();
return false;
}
});

I was looking for an answer that restricted input to only alphanumeric characters, but still allowed for the use of control characters (e.g., backspace, delete, tab) and copy+paste. None of the provided answers that I tried satisfied all of these requirements, so I came up with the following using the input event.
$('input').on('input', function() {
$(this).val($(this).val().replace(/[^a-z0-9]/gi, ''));
});
Edit:
As rinogo pointed out in the comments, the above code snippet forces the cursor to the end of the input when typing in the middle of the input text. I believe the code snippet below solves this problem.
$('input').on('input', function() {
var c = this.selectionStart,
r = /[^a-z0-9]/gi,
v = $(this).val();
if(r.test(v)) {
$(this).val(v.replace(r, ''));
c--;
}
this.setSelectionRange(c, c);
});

Short answer: prevent the 'keypress' event:
$("input").keypress(function(e){
var charCode = !e.charCode ? e.which : e.charCode;
if(/* Test for special character */ )
e.preventDefault();
})
Long answer: Use a plugin like jquery.alphanum
There are several things to consider when picking a solution:
Pasted text
Control characters like backspace or F5 may be prevented by the above code.
é, í, ä etc
Arabic or Chinese...
Cross Browser compatibility
I think this area is complex enough to warrant using a 3rd party plugin. I tried out several of the available plugins but found some problems with each of them so I went ahead and wrote jquery.alphanum. The code looks like this:
$("input").alphanum();
Or for more fine-grained control, add some settings:
$("#username").alphanum({
allow : "€$£",
disallow : "xyz",
allowUpper : false
});
Hope it helps.

Use simple onkeypress event inline.
<input type="text" name="count" onkeypress="return /[0-9a-zA-Z]/i.test(event.key)">

Use HTML5's pattern input attribute!
<input type="text" pattern="^[a-zA-Z0-9]+$" />

Use regex to allow/disallow anything. Also, for a slightly more robust version than the accepted answer, allowing characters that don't have a key value associated with them (backspace, tab, arrow keys, delete, etc.) can be done by first passing through the keypress event and check the key based on keycode instead of value.
$('#input').bind('keydown', function (event) {
switch (event.keyCode) {
case 8: // Backspace
case 9: // Tab
case 13: // Enter
case 37: // Left
case 38: // Up
case 39: // Right
case 40: // Down
break;
default:
var regex = new RegExp("^[a-zA-Z0-9.,/ $#()]+$");
var key = event.key;
if (!regex.test(key)) {
event.preventDefault();
return false;
}
break;
}
});

Your textbox:
<input type="text" id="name">
Your javascript:
$("#name").keypress(function(event) {
var character = String.fromCharCode(event.keyCode);
return isValid(character);
});
function isValid(str) {
return !/[~`!##$%\^&*()+=\-\[\]\\';,/{}|\\":<>\?]/g.test(str);
}

Take a look at the jQuery alphanumeric plugin. https://github.com/KevinSheedy/jquery.alphanum
//All of these are from their demo page
//only numbers and alpha characters
$('.sample1').alphanumeric();
//only numeric
$('.sample4').numeric();
//only numeric and the .
$('.sample5').numeric({allow:"."});
//all alphanumeric except the . 1 and a
$('.sample6').alphanumeric({ichars:'.1a'});

this is an example that prevent the user from typing the character "a"
$(function() {
$('input:text').keydown(function(e) {
if(e.keyCode==65)
return false;
});
});
key codes refrence here:
http://www.expandinghead.net/keycode.html

I use this code modifying others that I saw. Only grand to the user write if the key pressed or pasted text pass the pattern test (match) (this example is a text input that only allows 8 digits)
$("input").on("keypress paste", function(e){
var c = this.selectionStart, v = $(this).val();
if (e.type == "keypress")
var key = String.fromCharCode(!e.charCode ? e.which : e.charCode)
else
var key = e.originalEvent.clipboardData.getData('Text')
var val = v.substr(0, c) + key + v.substr(c, v.length)
if (!val.match(/\d{0,8}/) || val.match(/\d{0,8}/).toString() != val) {
e.preventDefault()
return false
}
})

$(function(){
$('input').keyup(function(){
var input_val = $(this).val();
var inputRGEX = /^[a-zA-Z0-9]*$/;
var inputResult = inputRGEX.test(input_val);
if(!(inputResult))
{
this.value = this.value.replace(/[^a-z0-9\s]/gi, '');
}
});
});

Write some javascript code on onkeypress event of textbox.
as per requirement allow and restrict character in your textbox
function isNumberKeyWithStar(evt) {
var charCode = (evt.which) ? evt.which : event.keyCode
if (charCode > 31 && (charCode < 48 || charCode > 57) && charCode != 42)
return false;
return true;
}
function isNumberKey(evt) {
var charCode = (evt.which) ? evt.which : event.keyCode
if (charCode > 31 && (charCode < 48 || charCode > 57))
return false;
return true;
}
function isNumberKeyForAmount(evt) {
var charCode = (evt.which) ? evt.which : event.keyCode
if (charCode > 31 && (charCode < 48 || charCode > 57) && charCode != 46)
return false;
return true;
}

To replace special characters, space and convert to lower case
$(document).ready(function (){
$(document).on("keyup", "#Id", function () {
$("#Id").val($("#Id").val().replace(/[^a-z0-9\s]/gi, '').replace(/[_\s]/g, '').toLowerCase());
});
});

Yes you can do by using jQuery as:
<script>
$(document).ready(function()
{
$("#username").blur(function()
{
//remove all the class add the messagebox classes and start fading
$("#msgbox").removeClass().addClass('messagebox').text('Checking...').fadeIn("slow");
//check the username exists or not from ajax
$.post("user_availability.php",{ user_name:$(this).val() } ,function(data)
{
if(data=='empty') // if username is empty
{
$("#msgbox").fadeTo(200,0.1,function() //start fading the messagebox
{
//add message and change the class of the box and start fading
$(this).html('Empty user id is not allowed').addClass('messageboxerror').fadeTo(900,1);
});
}
else if(data=='invalid') // if special characters used in username
{
$("#msgbox").fadeTo(200,0.1,function() //start fading the messagebox
{
//add message and change the class of the box and start fading
$(this).html('Sorry, only letters (a-z), numbers (0-9), and periods (.) are allowed.').addClass('messageboxerror').fadeTo(900,1);
});
}
else if(data=='no') // if username not avaiable
{
$("#msgbox").fadeTo(200,0.1,function() //start fading the messagebox
{
//add message and change the class of the box and start fading
$(this).html('User id already exists').addClass('messageboxerror').fadeTo(900,1);
});
}
else
{
$("#msgbox").fadeTo(200,0.1,function() //start fading the messagebox
{
//add message and change the class of the box and start fading
$(this).html('User id available to register').addClass('messageboxok').fadeTo(900,1);
});
}
});
});
});
</script>
<input type="text" id="username" name="username"/><span id="msgbox" style="display:none"></span>
and script for your user_availability.php will be:
<?php
include'includes/config.php';
//value got from the get method
$user_name = trim($_POST['user_name']);
if($user_name == ''){
echo "empty";
}elseif(preg_match('/[\'^£$%&*()}{##~?><>,|=_+¬-]/', $user_name)){
echo "invalid";
}else{
$select = mysql_query("SELECT user_id FROM staff");
$i=0;
//this varible contains the array of existing users
while($fetch = mysql_fetch_array($select)){
$existing_users[$i] = $fetch['user_id'];
$i++;
}
//checking weather user exists or not in $existing_users array
if (in_array($user_name, $existing_users))
{
//user name is not availble
echo "no";
}
else
{
//user name is available
echo "yes";
}
}
?>
I tried to add for / and \ but not succeeded.
You can also do it by using javascript & code will be:
<!-- Check special characters in username start -->
<script language="javascript" type="text/javascript">
function check(e) {
var keynum
var keychar
var numcheck
// For Internet Explorer
if (window.event) {
keynum = e.keyCode;
}
// For Netscape/Firefox/Opera
else if (e.which) {
keynum = e.which;
}
keychar = String.fromCharCode(keynum);
//List of special characters you want to restrict
if (keychar == "'" || keychar == "`" || keychar =="!" || keychar =="#" || keychar =="#" || keychar =="$" || keychar =="%" || keychar =="^" || keychar =="&" || keychar =="*" || keychar =="(" || keychar ==")" || keychar =="-" || keychar =="_" || keychar =="+" || keychar =="=" || keychar =="/" || keychar =="~" || keychar =="<" || keychar ==">" || keychar =="," || keychar ==";" || keychar ==":" || keychar =="|" || keychar =="?" || keychar =="{" || keychar =="}" || keychar =="[" || keychar =="]" || keychar =="¬" || keychar =="£" || keychar =='"' || keychar =="\\") {
return false;
} else {
return true;
}
}
</script>
<!-- Check special characters in username end -->
<!-- in your form -->
User id : <input type="text" id="txtname" name="txtname" onkeypress="return check(event)"/>

just the numbers:
$('input.time').keydown(function(e) { if(e.keyCode>=48 &&
e.keyCode<=57) {
return true; } else {
return false; } });
or for time including ":"
$('input.time').keydown(function(e) { if(e.keyCode>=48 &&
e.keyCode<=58) {
return true; } else {
return false; } });
also including delete and backspace:
$('input.time').keydown(function(e) { if((e.keyCode>=46 &&
e.keyCode<=58) || e.keyCode==8) { return true; } else {
return false; } });
unfortuneatly not getting it to work on a iMAC

Wanted to comment on Alex's comment to Dale's answer. Not possible (first need how much "rep"? That wont happen very soon.. strange system.)
So as an answer:
Backspace can be added by adding \b to the regex definition like this: [a-zA-Z0-9\b].
Or you simply allow the whole Latin range, including more or less anything "non exotic" characters (also control chars like backspace): ^[\u0000-\u024F\u20AC]+$
Only real unicode char outside latin there is the euro sign (20ac), add whatever you may need else.
To also handle input entered via copy&paste, simply also bind to the "change" event and check the input there too - deleting it or striping it / giving an error message like "not supported characters"..
if (!regex.test($j(this).val())) {
alert('your input contained not supported characters');
$j(this).val('');
return false;
}

Restrict specials characters on keypress. Here's a test page for key codes: http://www.asquare.net/javascript/tests/KeyCode.html
var specialChars = [62,33,36,64,35,37,94,38,42,40,41];
some_element.bind("keypress", function(event) {
// prevent if in array
if($.inArray(event.which,specialChars) != -1) {
event.preventDefault();
}
});
In Angular, I needed a proper currency format in my textfield. My solution:
var angularApp = angular.module('Application', []);
...
// new angular directive
angularApp.directive('onlyNum', function() {
return function( scope, element, attrs) {
var specialChars = [62,33,36,64,35,37,94,38,42,40,41];
// prevent these special characters
element.bind("keypress", function(event) {
if($.inArray(event.which,specialChars) != -1) {
prevent( scope, event, attrs)
}
});
var allowableKeys = [8,9,37,39,46,48,49,50,51,52,53,54,55,56
,57,96,97,98,99,100,101,102,103,104,105,110,190];
element.bind("keydown", function(event) {
if($.inArray(event.which,allowableKeys) == -1) {
prevent( scope, event, attrs)
}
});
};
})
// scope.$apply makes angular aware of your changes
function prevent( scope, event, attrs) {
scope.$apply(function(){
scope.$eval(attrs.onlyNum);
event.preventDefault();
});
event.preventDefault();
}
In the html add the directive
<input only-num type="text" maxlength="10" id="amount" placeholder="$XXXX.XX"
autocomplete="off" ng-model="vm.amount" ng-change="vm.updateRequest()">
and in the corresponding angular controller I only allow there to be only 1 period, convert text to number and add number rounding on 'blur'
...
this.updateRequest = function() {
amount = $scope.amount;
if (amount != undefined) {
document.getElementById('spcf').onkeypress = function (e) {
// only allow one period in currency
if (e.keyCode === 46 && this.value.split('.').length === 2) {
return false;
}
}
// Remove "." When Last Character and round the number on blur
$("#amount").on("blur", function() {
if (this.value.charAt(this.value.length-1) == ".") {
this.value.replace(".","");
$("#amount").val(this.value);
}
var num = parseFloat(this.value);
// check for 'NaN' if its safe continue
if (!isNaN(num)) {
var num = (Math.round(parseFloat(this.value) * 100) / 100).toFixed(2);
$("#amount").val(num);
}
});
this.data.amountRequested = Math.round(parseFloat(amount) * 100) / 100;
}
...

You don't need jQuery for this action
You can achieve this using plain JavaScript, You can put this in the onKeyUp event.
Restrict - Special Characters
e.target.value = e.target.value.replace(/[^\w]|_/g, '').toLowerCase()
Accept - Number only
e.target.value = e.target.value.replace(/[^0-9]/g, '').toLowerCase()
Accept - Small Alphabet only
e.target.value = e.target.value.replace(/[^0-9]/g, '').toLowerCase()
I could write for some more scenarios but I have to maintain the specific answer.
Note It will work with jquery, react, angular, and so on.

$(this).val($(this).val().replace(/[^0-9\.]/g,''));
if( $(this).val().indexOf('.') == 0){
$(this).val("");
}
//this is the simplest way
indexof is used to validate if the input started with "."

[User below code to restrict special character also
$(h.txtAmount).keydown(function (event) {
if (event.shiftKey) {
event.preventDefault();
}
if (event.keyCode == 46 || event.keyCode == 8) {
}
else {
if (event.keyCode < 95) {
if (event.keyCode < 48 || event.keyCode > 57) {
event.preventDefault();
}
}
else {
if (event.keyCode < 96 || event.keyCode > 105) {
event.preventDefault();
}
}
}
});]

Allow only numbers in TextBox (Restrict Alphabets and Special Characters)
/*code: 48-57 Numbers
8 - Backspace,
35 - home key, 36 - End key
37-40: Arrow keys, 46 - Delete key*/
function restrictAlphabets(e){
var x=e.which||e.keycode;
if((x>=48 && x<=57) || x==8 ||
(x>=35 && x<=40)|| x==46)
return true;
else
return false;
}

/**
* Forbids special characters and decimals
* Allows numbers only
* */
const numbersOnly = (evt) => {
let charCode = (evt.which) ? evt.which : evt.keyCode;
if (charCode === 46 && charCode > 31 && (charCode < 48 || charCode > 57)) {
return false;
}
let inputResult = /^[0-9]*$/.test(evt.target.value);
if (!inputResult) {
evt.target.value = evt.target.value.replace(/[^a-z0-9\s]/gi, '');
}
return true;
}

In HTML:
<input type="text" (keypress)="omitSpecialChar($event)"/>
In JS:
omitSpecialChar(event) {
const keyPressed = String.fromCharCode(event.keyCode);
const verifyKeyPressed = /^[a-zA-Z\' \u00C0-\u00FF]*$/.test(keyPressed);
return verifyKeyPressed === true;
}
In this example it is possible to type accents.

$(document).ready(function() {
$('#Description').bind('input', function() {
var c = this.selectionStart,
r = /[^a-z0-9 .]/gi,
v = $(this).val();
if (r.test(v)) {
$(this).val(v.replace(r, ''));
c--;
}
this.setSelectionRange(c, c);
if (!(checkEmpty($("#Description").val()))) {
$("#Description").val("");
} //1Apr2022 code end
});
$('#Description').on('change', function() {
if (!(checkEmpty($("#Description").val()))) {
$("#Description").val("");
} //1Apr2022 code end
});
});
function checkEmpty(field) { //1Apr2022 new code
if (field == "" ||
field == null ||
field == "undefinied") {
return false;
} else if (/^\s*$/.test(field)) {
return false;
} else {
return true;
}
}

A more enhanced form would be
$('input[type=text]').on('input', function() {
var c = this.selectionStart,
r = /[^a-z ]/gi,
v = $(this).val();
if(r.test(v)) {
$(this).val(v.replace(r, ''));
c--;
}
this.setSelectionRange(c, c);
});
Because it will allow you to enter space as well and it will only target the input fields with type text and wont bother the other input fields like email, password etc as normally we need special characters in email and password field

How to restrict a field to take only 4 numeric characters as input?

I wanted a text field to take only numbers ans some control keys and number should be exactly four digit long, not less not more. My validation code is
function checkValidInput()
{
$(".validateYearTextBox").keydown(function(event)
{
// Allow only delete, backspace,left arrow,right arraow and Tab
if (
event.keyCode == 46 //delete
|| event.keyCode == 8 //backspace
|| event.keyCode == 37 //leftarow
|| event.keyCode == 39 //rightarrow
|| event.keyCode == 9 //tab
)
{
// let it happen, don't do anything
}
else {
// Ensure that it is a number and stop the keypress
if ((event.keyCode < 48 || event.keyCode > 57) && (event.keyCode <96 ||event.keyCode > 105) ) {
event.preventDefault();
}
}
});
$(".validateYearTextBox").keyup(function(event)
{
var val = $(this).val();
if (val.length > 4){
alert ("Max length is 4");
val = val.substring(0, valore.length - 1);
$(this).val(val);
$(this).focus();
return false;
}
});
}
Here, my first validation is working, but my send one is not working.
I am calling this validation function in my aspx page like this
<script type="text/javascript">
$(document).ready(function(){
checkValidInput();
}
</script>
What is going wrong?

Simplify it:
function checkValidInput() {
// Allow only delete, backspace, left arrow, right arrow,
// Tab, ctrl+v and numbers
$(".validateYearTextBox").keydown(function(event) {
if (!((event.keyCode == 46 ||
event.keyCode == 8 ||
event.keyCode == 37 ||
event.keyCode == 39 ||
event.keyCode == 9) ||
(event.ctrlKey && event.keyCode == 86) || // Edit: Added to allow ctrl+v
$(this).val().length < 4 &&
((event.keyCode >= 48 && event.keyCode <= 57) ||
(event.keyCode >= 96 && event.keyCode <= 105)))) {
// Stop the event
event.preventDefault();
return false;
}
});
// Edit: Added validate after copy+paste.
// This removes non-numeric characters and truncates the length
// to 4 if the user copy + pasted.
$(".validateYearTextBox").change(function(event) {
var value = $(this).val();
value = value.replace(/[^0-9]/g,'');
value = value.substr(0,4);
$(this).val(value);
});
}
$(document).ready(function() {
checkValidInput();
});
http://jsfiddle.net/nwellcome/687kD/
Edit: Personally I like the Masked Input jQuery plugin but that might be a heavy-handed solution if this is all you need to do.

There are many, many jQuery plugins that already do this in one form or another.
One that does mostly1 what you want is Masked Input Plugin. If you can, I recommend using something existing, working and proven, rather than reinventing.
1 The only part that it doesn't seem to do is display an error if a user tries to enter more than n characters but I'm sure you could modify the plugin or add a length check to the <input>

Use regular expression :
enter code here
function validator(elem,msg)
{
var exp=/^([0-9]+)$/; //it only allows for numbers
if(elem.value.match(exp))
{return true;}
else
{
alert(msg);
elem.focus();
return false;
}
}
the html code :
enter code here
<html><head>
<script src="javasript.js" type="text/javascript">
</head>
<body>
<form method=POST>
<input type='text' maxlength=4 name='num' id='num'>
<input type='submit' value=OK onClick="validator(document.getElementById('num'),'Only four numbers and numbers only!');">
</form> //the maxlength in input text tag restrict the maximum length of the input
</body></html>

Here's a simple way of doing it. Stores the old text before an event changes the text. Then check to see if the new text is valid or not. If it isn't, then revert back to the old text. To further ensure the maximum of 4 characters, add a maxlength attribute to all <input type="text"> elements.
jQuery.fn.forceNumericOnly = function() {
return this.each(function() {
var oldText;
$(this).keyup(function(e) {
var newText = $(this).val();
if (newText != "" && (isNaN(newText) || val.length > 4))
$(this).val(oldText);
else
oldText = $(this).val();
})
$(this).blur(function(e) {
var newText = $(this).val();
if (newText != "" && (isNaN(newText) || val.length > 4))
$(this).val(newText = oldText);
else
oldText = $(this).val();
});
})
};
$(".validateYearTextBox").forceNumericOnly();

if (document.ExamEntry.examnum.value=="") {
msg+="You must enter your examination number \n";
document.ExamEntry.examnum.focus();
document.getElementById('examnum').style.color="red";
result = false;
}

$('.numeric').keypress(function(e) {
var verified = (e.which == 8 || e.which == undefined || e.which == 0) ? null : String.fromCharCode(e.which).match(/[^0-9]/);
if (verified || e.delegateTarget.value.length>3 || e.ctrlKey ==true) { if(e.which!=8 ){e.preventDefault();}}
}).on('paste',function(e){ e.preventDefault();});
Here add class=numeric to input text box'. it will allow only 4 digits if you want to limit size to 2 digits change to e.delegateTarget.value.length>1 and so on as index starts from zero

Use HTML input maxlength attribute for this and also set the size value of fixing width 4 in same input size attribute.
<input type="text" maxlength="4" size="4">

Here is a simple answer that takes care of copy paste and all.
$(document).on("input", ".validateYearTextBox", function() {
var value = this.value
value = value.replace(/\D/g,'');
for (i = 0; i < value.length; i++) {
if (i > 3) {
value = value.replace(value[i], '')
}
}
});

do an alert on keyup only if the key is a letter or number

I would like to show an alert on keyup event but only if the key was a letter or a number, not for shift,tab etc.
<input type='text' id='hi />
or for any key except for tab, shift, ctrl, enter
anybody knows how ?

You will have to attach an "keyup" event to the textbox and inside the event check for the keycodes you want:
$("#hi").bind("keyup", function(e) {
//on letter number
if (e.which <= 90 && e.which >= 48)
{
alert('hello');
}
});

If you want to check which character was typed, keyup is the wrong event. Only the keypress event can reliably tell you anything about the character typed. You can do it as follows:
$("#hi").keypress(function(e) {
var charTyped = String.fromCharCode(e.which);
if (/[a-z\d]/i.test(charTyped)) {
alert("Letter or number typed: " + charTyped);
}
});

This appended code accounts for numbers, characters, and digits from the numpad:
document.querySelector(selector).addEventListener('keypress', function() {
if (e.which <= 90 && e.which >= 48 || e.which >= 96 && e.which <= 105) {
alert('keycode ' + e.which + ' triggered this event');
//do whatever
}
});

That's what the onkeypress event is for, it only fires if you press a key that produces a value. MDN Docs.

I never liked the key code validation. My approach was to see if the input have text (any character), confirming that the user is entering text and no other characters.
$('#input').on('keyup', function() {
var words = $(this).val();
// if input is empty, remove the word count data and return
if(!words.length) {
$(this).removeData('wcount');
return true;
}
// if word count data equals the count of the input, return
if(typeof $(this).data('wcount') !== "undefined" && ($(this).data('wcount') == words.length)){
return true;
}
// update or initialize the word count data
$(this).data('wcount', words.length);
console.log('user tiped ' + words);
// do you stuff...
});
<html lang="en">
<head>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
</head>
<body>
<input type="text" name="input" id="input">
</body>
</html>

You can check if the key code is between the range of characters you want to allow.
<input id="textbox" type='text' id='hi' />
$("#textbox").keypress(function (e){
if (e.which <= 90 && e.which >= 48)
{
alert('Letter or number click');
}
});

<input type="text" id="hi" onkeypress="keyPress()" />
function keyPress(e){
var key, x = e || window.event; key = (x.keyCode || x.which);
if(key <= 90 && key >= 48){
alert("Key pressed");
}
}