How can I listen to document.hasFocus() without using an interval?

I want to check if the user changed the view of the current tab, that's why I am testing with if condition on document.hasFocus() and if it's equal to False, then I send an Axios(ajax) request to the backend..

Right now I am using document.hasFocus() with setInterval() function! In my case and using the setInterval function, the function checkFocus got triggered every 2 Seconds and checks if the user hasFocus.

The result of this is => if the user changes the tab.. => every 2 seconds an ajax request is sent .. (because of the setInterval) While I want the event to be triggered only 1 time. I want to send only 1 ajax request Each time the user loses the focus..

That's why I can"t use the SetInterval Function. My question is: How can I Listen to document.hasFocus without using SetInterval Function?

Here is my code:

setInterval( checkFocus, 200 );    function checkFocus() {        if ( document.hasFocus() == false ) {              axios.post(url).then(function(response){              }).catch(function(error)  {                  window.alert("Ouch an unexpected error has occurred. Reload the page and try again");              });      }   }  

https://stackoverflow.com/questions/65819464/how-can-i-listen-to-document-hasfocus-without-using-an-interval January 21, 2021 at 08:10AM