Hooking a synchronous event handler on a form submit button in JS

I'm working on a security project in Javascript (something I honestly have not used), and I'm having some trouble with EventListeners.

My code looks something like this:

function prevclick(evt) {
evt.preventDefault();
document.loginform.submitbtn.removeEventListener('click',prevclick,false);
var req = new XMLHttpRequest();
req.open("GET","testlog.php?submission=complete",false);
req.send();
document.loginform.submitbtn.click(); //tried this and loginform.submit()
}

document.loginform.submitbtn.addEventListener('click',prevclick,false);

But the problem is, the submit button doesn't submit the form on the first click (it does, however, send the http request on the first click), and on the second click of the submit button, it works as normal.

I think there is a problem with the synchronization, but I do need to have 开发者_StackOverflow中文版the request processed before forwarding the user to the next page.

Any ideas on this would be great.

remove the evt.preventDefault() line. And delete the last line of the function.