JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery-validate/1.15.0/jquery.validate.js"></script>
<form id="myform">
    <input type="text" name="foo[]" />
    <br />
    <input type="text" name="foo[]" />
    <br />
	<input type="text" name="foo[]" />
    <br />
	<input type="text" name="foo[]" />
    <br />
    <br />
    <input type="submit" />
</form>

JavaScript

$(document).ready(function () {

    $('#myform').validate({
        rules: {
            'foo[]': {
                required: true
            }
        }
    });

});