JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://code.jquery.com/jquery-2.1.4.js"></script>
<script src="http://ajax.aspnetcdn.com/ajax/jquery.validate/1.14.0/jquery.validate.js"></script>
<form id="myform">
    <input type="text" name="foo" />
    <br />
    <input type="text" name="bar" />
    <br />
    <br />
    <input type="submit" />
</form>

JavaScript

$(document).ready(function() {

    $('#myform').validate({
        rules: {
            foo: {
                required: true
            },
            bar: {
                required: true
            }
        },
        messages: {
            foo: {
                required: function(element) {
				    var message = "required default message";
					if ($('[name="bar"]').is(':filled')) {
					    message = "custom message";
					};
					return message;
				}
            },
            bar: {
                required: "required field"
            }
        }
    });

});