How to run function of parent window when child window closes?

Question

I am calling the javascript window.open() function to load another url in a pop up. Once the users is finished it takes them to the last page that has a link that says close

Answer 1

I know this post is old, but I found that this really works well:

window.onunload = function() {
    window.opener.location.href = window.opener.location.href;
};

The window.onunload part was the hint I found googling this page. Thanks, @jerjer!