Answers for "form submit event"

js form submit listener

document.getElementById("#myFormId").addEventListener("submit", function(e){
    if(!isValid){
        e.preventDefault();    //stop form from submitting
    }
  	//do whatever an submit the form
});

form confirm before submit

<form 
    method="post"
    onSubmit="return confirm('Are you sure you wish to delete?');">
...
</form>