How to hijack an event handler?

How can I invoke an event handler in Javascript whenever the page url changes?

• In this event handler I have to invoke another method which takes up some time to "do its work" and then I want the page to navigate. Any ideas are highly welcomed.

• Answer:

  https://developer.mozilla.org/en-US/docs/Web/Reference/Events/beforeunload - though this will fire on page refresh as well, not just url change. https://developer.mozilla.org/en-US/docs/Web/Reference/Events/unload - -ditto- https://developer.mozilla.org/en-US/docs/Web/Reference/Events/hashchange - only for the hash fragment. Browser compatibility for beforeunload: https://developer.mozilla.org/en-US/docs/Web/API/Window.onbeforeunload#Browser_compatibility Browser compatibility for hashchange: https://developer.mozilla.org/en-US/docs/Web/API/Window.onhashchange#Browser_compatibility The function that takes time, execute it completely synchronously inside the event handler. That could work