JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://ajax.aspnetcdn.com/ajax/jquery.validate/1.8.1/jquery.validate.min.js"></script>
<script src="http://ajax.aspnetcdn.com/ajax/jquery.validate/1.8.1/additional-methods.min.js"></script>
<form id="my-form" action="#" method="post">
    <input id="my-field" name="my-field" type="text"></input><br />
    <input type="submit" value="Submit" />
</form>

JavaScript

$.validator.addMethod("regexp", function(value, element, pattern) {
    return this.optional(element) || pattern.test(value);
}, "Field contains invalid characters.");

$("#my-form").validate({
    rules: {
        "my-field": {
            required: true,
            regexp: /^[0-9a-zA-Z_]*$/
        }
    }
});