[jQuery] Intercept user submission

[adexcube]

Hi,
I'm using a bespoke software which I can't access directly into the
code that produce.
I'm adding functionalities with jquery but I need to intercept all
user submissions.
At the moment the software produces this function

function submitForm() {

if (typeof validateIsSingleSubmit == 'function') {

 if (validateIsSingleSubmit() == false) {

 return;
 }
 }
 document.userInput.submit();
}
and this is the form header

<form action="" method="post" name="userInput" id="userInput">

I've tried

if(document.userInput.onSubmit()){
        return false;
}

but the submission doesn't stop.


Thanks