Function (called from setTimeout) not returning value

Function (called from setTimeout) not returning value

I'm learning JavaScript by writing a Chrome extension for a website. The
website has a section that displays a list of 4 videos, with a button to
load more videos. When you click this button, it loads a new list of
videos via an AJAX call.
I have a function, getNextVideo(), which gets the URL of the next video in
the list. For example, if you are on the third video, then it'll grab the
URL for the fourth video. If you're on the fourth video, then it'll
simulate a click (which loads the new list of videos) via a function
getNextVideoList() and then grab the first in the newly loaded list after
a 1s timeout to wait for the DOM to update (I tried to use mutation
observers but it was too complicated for my skill level).
function getNextVideo()
{
if (getVideoPosition() == 4)
{
function ad()
{
getVideo(1);
}
setTimeout(ad, 1000);
getNextVideoList();
}
else
{
var index = getVideoPosition() + 1;
return getVideo(index);
}
}
getVideoPosition() gets the index of the video in the list using some
simple jQuery nth-child selectors. It returns the values 1, 2, 3, or 4.
getVideo(n) takes the index of the video (1, 2, 3, or 4) and returns the
URL of that video. The returned value looks like this in the console:
"http://video.example.com/video-id"
My problem is that when I run getNextVideo() on a video that is 4th in the
queue, I get undefined returned in my console. How do I make the
getNextVideo() function return the URL of the first video in the list
after the AJAX call and subsequent DOM update?