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sessions.onChanged

files/en-us/mozilla/add-ons/webextensions/api/sessions/onchanged/index.md

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Fired whenever the list of closed tabs or windows changes.

Syntax

js-nolint
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.

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);

{{WebExtExamples}}

Browser compatibility

{{Compat}}

[!NOTE] This API is based on Chromium's chrome.sessions API.

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