Allowing only Alphanumeric values [duplicate]

The better solution might be to go with regular expression based checks. Example below will limit only alphanumeric characters in the field with id text:

$('#text').keypress(function (e) {
    var regex = new RegExp("^[a-zA-Z0-9]+$");
    var str = String.fromCharCode(!e.charCode ? e.which : e.charCode);
    if (regex.test(str)) {
        return true;
    }

    e.preventDefault();
    return false;
});