https://github.com/look997/PNYT

Code
https://github.com/look997/PNYT/blob/master/pnyt.user.js

I have a small script to YouTube.

The problem started since the videos load without refreshing the page.

popstate event is not enough - it works only when the back / forward-button.

The "setTOFun ()" should be performed each time you charge the new film.

How to do it?

Re: @look997:
You can use a Mutation Observer to watch for changes in the page. Here is an example:

https://greasyfork.org/en/scripts/4346-youtube-remove-list-from-watch-urls/code

On line 32, call your script to parse through the list of added nodes.

Re: @look997:
Could use setInterval and check if the element exists before continuing

If the url is changing in the address bar, but a new page isn't being loaded, they could be modifiying the history. You can use window.onpopstate to detect the change.

Re: @sizzle:
My bad. I didn't read your entire post. You already used popstate. I've had this problem on a similar page. The onpopstate doesn't help. The page doesn't reload, but the url changes.

This might help (you might have to use @run-at document-start):

var pushState = window.history.pushState;
window.history.pushState = window.history.replaceState = function (stateObj, title, url) {
    console.log('changed to: ' + url);
    pushState(stateObj, title, url);
};