JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://raw.github.com/jzaefferer/jquery-validation/master/jquery.validate.js"></script>
<form id="signup" action="/action">
<input name="fullname" type="text" />
<input type="submit">
</form>

JavaScript

$(document).ready(function() {
    var fullname_invalid = function(value) {
        return value === "Mark";
    }


    $.validator.addMethod("custom_fullname", function(value, element) {
        return fullname_invalid(value);
    }, 'Your Name should be entered like: "Mark"');

    $('#signup').validate({
        rules: {
            fullname: {
                required: true,
                custom_fullname: true
            }
        }
    });

    $('#signup').on('submit', function(event) {
        event.preventDefault();
    });
});