Detect if application has been closed or paused

Question

I'm developing my first FirefoxOS app and I need it to backup some data when the user closes or pauses the app. How can I detect this?

I've tried "window.onunload" but it doesn't seem to work.

Thank you.

Answer 1

You should be able to use page visibility API for background switch.

document.addEventListener("visibilitychange", function () {
if (document.hidden) {
  console.log("App is hidden");
} else {
  console.log("App has focus");
} });

Answer 2

Event launch visible only if app lost focus.

document.addEventListener('visibilitychange', function() {
  if (document['visibilityState'] == "hidden") {
    //code if is user out app, no close app
  } else if(document['visibilityState'] == 'visible') {
    //code if user return on app
  }
}, false);