sample js code

sample.js

(function (nu) {
    nu.ready(function () {
        var elements = nu.querySelectorAll('.nl-widget-sleek-form-contact');

        for (var i=0; i < elements.length; i++) {
            var form = nu.querySelector('form', elements[i]);

            nu.addEventListener(form, 'submit', function (e) { console.log('a');
                nu.querySelector('button', e.target).setAttribute('disabled', 'disabled');
            });

            let eventSrv = ni.provider.get('service').get('event');
            let events = ni.provider.get('const').get('plugin.form.events');
            let submitDone = events.SUBMIT_DONE.replace('%s', form.getAttribute('data-form-id'));

            // when the form is submit, we should update the form
            eventSrv.on(submitDone, submitDone, function (e) { console.log('b');
                nu.querySelector('button', e.form).removeAttribute('disabled');
            });
        }
    });
})(nu)