Only Alphabets and Numbers allowed in text field

<input type="text" id="txtName"/>

<span id="lblError" style="color: red"></span>

<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>

<script type="text/javascript">

    $(function () {

        $("#txtName").keypress(function (e) {

            var keyCode = e.keyCode || e.which;

 

            $("#lblError").html("");

 

            //Regex for Valid Characters i.e. Alphabets and Numbers.

            var regex = /^[A-Za-z0-9 ]+$/;

 

            //Validate TextBox value against the Regex.

            var isValid = regex.test(String.fromCharCode(keyCode));

            if (!isValid) {

                $("#lblError").html("Only Alphabets and Numbers allowed.");

            }

 

            return isValid;

        });

    });

</script>