sessions.onChanged

Fired whenever the list of closed tabs or windows changes.

Syntax

js
browser.sessions.onChanged.addListener(listener)
browser.sessions.onChanged.removeListener(listener)
browser.sessions.onChanged.hasListener(listener)

Events have three functions:

addListener(listener)

Adds a listener to this event.

removeListener(listener)

Stop listening to this event. The listener argument is the listener to remove.

hasListener(listener)

Check whether listener is registered for this event. Returns true if it is listening, false otherwise.

addListener syntax

Parameters

listener

The function called when this event occurs. It's passed no parameters.

Browser compatibility

Chrome
Edge
Firefox
Opera
Safari
Firefox for Android
Safari on iOS
onChanged

Examples

This very annoying extension listens for onChanged, then immediately restores the most recently closed session, thus making it impossible to close windows or tabs:

js
function restoreSession(sessionInfos) {
  if (!sessionInfos.length) {
    console.log("No sessions found");
    return;
  }
  let sessionInfo = sessionInfos[0];
  if (sessionInfo.tab) {
    browser.sessions.restore(sessionInfo.tab.sessionId);
  } else {
    browser.sessions.restore(sessionInfo.window.sessionId);
  }
}

function onError(error) {
  console.log(error);
}

function restoreMostRecent() {
  let gettingSessions = browser.sessions.getRecentlyClosed({
    maxResults: 1,
  });
  gettingSessions.then(restoreSession, onError);
}

browser.sessions.onChanged.addListener(restoreMostRecent);

Note: This API is based on Chromium's chrome.sessions API.