Enable button after form filled Javascript - Swift

Question

I was able to fill successfully a form, inserting Username and Password, but the "Submit" button is still gray...

Do you have any suggestions?

webView.evaluateJavaScript("document.getElementById('userXS').value='\(user)'", completionHandler: nil)
webView.evaluateJavaScript("document.getElementById('passwordXS').value='\(pass)'", completionHandler: nil)

This is the form group with the button that is not enabling:

 <div class="form-group">
                                        <div class="help-block text-center underlined">
                                            <a href="/adesioni/manageRecuperoDatiRegistrazione.do?adfgenDispatchAction=resetPasswordUtente&amp;org.apache.struts.taglib.html.CANCEL=true&amp;adfgenResetSession=true"><strong>Password Dimenticata ?</strong></a>
                                        </div>
                                        <div class="form-group" data-cg-busy="{promise:loginPromiseXs,templateUrl:'/opencms/opencms/system/modules/my.template/resources/busyTemplate_small.html'}" style="position: relative;">
                                            <button type="submit" class="btn btn-lg colorButtonBlue fontWhite btn-block" data-ng-disabled="checkLogin(formXS)" disabled="disabled">ENTRA</button>
                                        <div class="cg-busy cg-busy-backdrop cg-busy-backdrop-animation ng-hide ng-scope" ng-show="$cgBusyIsActive()"></div><div class="cg-busy cg-busy-animation ng-hide ng-scope" ng-show="$cgBusyIsActive()"><div class="padding-left15-lg" style="position: absolute; top: 0px; left: 0px; right: 0px; bottom: 0px; background-repeat: no-repeat no-repeat;">
    <img class="center-img spinner-effect" src="/opencms/opencms/immagini/rifacimento_nuovo_portale/Eclipse_piccolo.gif">
</div> </div></div>

                                        <div class="help-block text-center">Sei un nuovo utente?
                                            <a class="underlined" href="/opencms/opencms/registrazione.html"><strong> Registrati</strong>
                                                            </a>
                                        </div>
                                    </div>

I found that on the row "button" there is "disabled" element. There is something that I can do? Thank you!