Run JavaScript code on window close or page refresh?

There is both window.onbeforeunload and window.onunload, which are used differently depending on the browser. You can assign them either by setting the window properties to functions, or using the .addEventListener:

window.onbeforeunload = function(){
   // Do something
}
// OR
window.addEventListener("beforeunload", function(e){
   // Do something
}, false);
   

Usually, onbeforeunload is used if you need to stop the user from leaving the page (ex. the user is working on some unsaved data, so he/she should save before leaving). onunload isn’t supported by Opera, as far as I know, but you could always set both.

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