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storage.StorageArea.onChanged

Fires when one or more items in a storage area change. Compared to storage.onChanged, this event enables you to listen for changes in one of the storage areas: local, managed, session, and sync.

Syntax

// local can also be sync, managed, or session
browser.storage.local.onChanged.addListener(callback)
browser.storage.local.onChanged.removeListener(listener)
browser.storage.local.onChanged.hasListener(listener)

Events have three functions:

addListener(callback)

Adds a listener to this event.

removeListener(listener)

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

hasListener(listener)

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

addListener syntax

Parameters

callback

The function called when this event occurs. The function is passed these arguments:

changes

object. Object describing the change. This contains one property for each key that changed. The name of the property is the name of the key that changed, and its value is a storage.StorageChange object describing the change to that item.

Examples

/*
Log the old value and its new value of
changes in the local storage.
*/
function logStorageChange(changes) {

  const changedItems = Object.keys(changes);

  for (const item of changedItems) {
    console.log(`${item} has changed:`);
    console.log("Old value: ", changes[item].oldValue);
    console.log("New value: ", changes[item].newValue);
  }
}

browser.storage.local.onChanged.addListener(logStorageChange);

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
onChanged 73 Yes 101 ? Yes 14 ? ? 101 ? 15 ?

Note: This API is based on Chromium's chrome.storage API. This documentation is derived from storage.json in the Chromium code.

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https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/storage/StorageArea/onChanged