check if page is cached jacascript code example

Example: JS how to determine if page was cached

// https://developer.mozilla.org/en-US/docs/Web/API/PageTransitionEvent
window.addEventListener('pageshow', myFunction);

function myFunction(event) { 
  if (event.persisted) {
    alert("The page was cached by the browser");
  } else {
    alert("The page was NOT cached by the browser");
  }
}