Custom evaluation before submit of multi step form

Hi,

Trying to evaluate a multi-step form with some custom javascript when user hits Submit at the last step.

It works fine for single-step forms with:

	event.preventDefault();
	event.stopImmediatePropagation();

But for multi-step forms the form submission doesn’t stop with this method and continues to send ajax request with POST.
Is there a way to intercept a multi-step form submission with javascript, then make some custom validation and if returned true continue with submission?

I have tried to create MutationObserver to track the form steps with no success, please see below:

 // Runs on jQuery( document ).ready 
  function init(form){
  	// Forminator has totaly differnt behaviors for the forms that contains pagination
  	// we need also implement differnt solution for them
  	const totalSteps = form.querySelectorAll("div[data-step]").length
  	if(totalSteps > 0 ){
  		const targetNode = document.querySelector('div.forminator-pagination-steps[role=tablist]')
  		const config = {
  			childList: true,
  		}
  		const observer = new MutationObserver(breakMenuAddedCallback)
  		observer.observe(targetNode,config)
  		form.addEventListener("click", e => paginationSubmitHandler(e, totalSteps));
  	} else {
        form.addEventListener("submit",submitHandler);
    }
  }

  function paginationSubmitHandler(event, totalSteps){
	  var target = event.target
	  if( target.getAttribute('id') !='forminator-submit'){
		  return;
	  }
	 // Check if it is last page
	  if(step == (totalSteps -1)) {
		  submitHandler(event)
	  }
  }
  
  function submitHandler(event){
	event.preventDefault();
	event.stopImmediatePropagation();
  console.log("Reached hideLoader()");
	hideLoader()
	showButtons("sbid-btn")
	hideButtons('open')
	setMessage("Välj hur du vill legitimera dig")
	hideSignOption(false)
  }
  var step = 0;
  function breakMenuAddedCallback(mutationList, observer){
	  mutationList.forEach(mutation => {
		  if(mutation.addedNodes.length){
			  mutation.addedNodes.forEach(node => {
				// Observing the step buttons
				if( node.classList.contains('forminator-step')){
					const config = {attributes : true }
					const observerInstance = new MutationObserver( (mutations, o) => {
						mutations.forEach(mutation => {
							if(mutation.attributeName == 'aria-selected'){
								setInterval(() => {
									const page = document.querySelector('button.forminator-step[aria-selected=true]')
									if(page == null) {
										return
									}
									step = page.getAttribute('data-nav')
								}, 0)
								
							}
						});
					})
					observerInstance.observe(node, config)
				  }
			  });
		  }
	  });
  }