JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://ajax.aspnetcdn.com/ajax/jquery.validate/1.13.1/jquery.validate.js"></script>
<script src="http://ajax.aspnetcdn.com/ajax/jquery.validate/1.13.1/additional-methods.js"></script>
<form id="my_form">
    1 <input type="text" name="fieldOne" class="ccustom" /><br />
    2 <input type="text" name="fieldTwo" /><br />
    <button type="submit">Submit</button>
</form>

JavaScript

$(function () {
    $.validator.addClassRules("ccustom", {
        required: true,
        remote: function(element) {
        console.log('here');
            return {
                url : '/echo/json/',
                type:'post',
                data: {
                    json: JSON.stringify(
                        ($(element).val() == "123")
                            ? "true" :
                            "Must be 123"),
                    delay: 0.3
                }               
            }
        }
    });

    $("#my_form").validate();
});