JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://ajax.aspnetcdn.com/ajax/jquery.validate/1.13.1/jquery.validate.js"></script>
<form id="myform">
    <div class="price-row"> <span>A-text</span>
        <input type="text" id="input-A" name="A" />
    </div>
    <div class="price-row"> <span>B-text</span>

        <input type="text" id="input-B" name="B" />
    </div>
    <input type="submit" />
</form>

JavaScript

$(document).ready(function () {

    $("#myform").validate({
        rules: {
            A: {
                required: {
                    depends: function (element) {
                        return $("#input-B").is(':filled');
                    }
                }
            },
            B: {
                required: {
                    depends: function (element) {
                        return $("#input-A").is(':filled');
                    }
                }
            }
        },
        submitHandler: function(form) {
            // for demo only
            alert('valid form');
            return false;
        }
    });

});