JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://ajax.aspnetcdn.com/ajax/jquery.validate/1.9/jquery.validate.min.js"></script>
<form name="frmCreateCM" action="something" method="post">
    <input type="text" name="reg_number[0]" value="" />
    <input type="text" name="reg_number[1]" value="" />
    <input type="text" name="reg_number[2]" value="" />
    <input type="submit" name="submit" value="submit" />
</form>

<div class="errormsg"></div>

JavaScript

$(document).ready(function() {

    // validate signup form on keyup and submit
    var validator = $("form[name='frmCreateCM']").validate({
        showErrors: function(errorMap, errorList) {
            $(".errormsg").html($.map(errorList, function(el) {
                return el.message;
            }).join(", "));
        },
        wrapper: "span"
    });

    $('[name^="reg_number"]').each(function() {
        $(this).rules('add', {
            required: true,
            minlength: 2,
            messages: {
                required: "Enter Reg Number",
                minlength: "Enter at least {0} characters",
            }
        })
    });

});