How to validate html textbox not to allow special characters and space?

This is my html:

 <input type="text" name="folderName">

Here, I want to validate the textbox value by not allowing to key in special characters and space. But it should allow underscore.

How to validate this textbox?



You may try to use this function:

<html xmlns="">
<head id="Head1" runat="server">
    <script type="text/javascript">
    function blockSpecialChar(e){
        var k;
        document.all ? k = e.keyCode : k = e.which;
        return ((k > 64 && k < 91) || (k > 96 && k < 123) || k == 8 || k == 32 || (k >= 48 && k <= 57));
    <form id="frm" runat="server">
      <input type="text" name="folderName"  onkeypress="return blockSpecialChar(event)"/>

Try like this

$(document).ready(function () {
var fn = $("#folderName").val();
    var regex = /^[0-9a-zA-Z\_]+$/

This return false for special chars and spaces and return true for underscore, digits and alphabets.



You may try to use this function:

<input class="form-control" onkeypress="return ((event.charCode > 64 && event.charCode < 91) || (event.charCode > 96 && event.charCode < 123) || event.charCode == 8 || event.charCode == 32 || (event.charCode >= 48 && event.charCode <= 57));" id="name" formControlName="name" type="text" autocomplete="off" value="">

It works for me.


You can use jQuery + jQuery Validation Plugin. That will make it that easy:

This will allow the user only to type letters plus underscore

 <input type="text" data-validation="alphanumeric" data-validation-allowing="_">

Link to the jQuery Plugin:


You have to create a javascript function that will do the validation. You could find severals exemple around the web. You could take a look on that website: javascript-validation and pay attention to the Email Validation in Javascript part (you will have to adapt a little).


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