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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