How to implement a failsafe page on pjax yii2?

Question

JavaScript

There is a page (yii2, pjax), the pjax area is updated every 10 seconds. But sometimes bad things happen (500 errors on the server/no connection to the web server).
I would like to implement such a mechanism - if the error is 500 / no connection, then report an error, but also update the page every 10 seconds.
In which direction to look, where to dig, tell me? In general, I would like to stay on pjax, because logic is sharpened for it.