Magento – Magento2 – How to execute validator on form

Yes you can validate your form explicitly and based on the status of the validation (success/failed) you can roll out your own callback actions. Hope am understanding you correctly and pointing you to the right direction.

<script type="text/javascript">
//<![CDATA[

    var contactForm = new VarienForm('contactForm', true);
    if (contactForm .validator.validate()){
        alert("Contact form is submitted and Validation Passed !"); //i love alerts more than console.log() as it works on all the browsers and versions
    }else{
        alert("Contact form is submitted and Validation Failed !");   
        jQuery(document).foundation('equalizer', 'reflow'); // assumed you have jQuery.noConflict(); before you call jQuery
    } 

//]]>
</script>

Use below code for submit and validate form using ajax

require([
    'jquery',
    'mage/mage',
    'Magento_Catalog/product/view/validation',
    'Magento_Catalog/js/catalog-add-to-cart'

], function ($) {
    'use strict';

    $('#custom_addtocart_form').mage('validation', {
        radioCheckboxClosest: '.nested',
        submitHandler: function (form) {
            jQuery.ajax({
                url: form.action,
                type: 'POST',
                dataType: 'json',
                data: form.serialize(),
                showLoader: true
            }).done(function (data) {
                return true;
            });

        }
    });


});