storage.onChanged

Fired when one or more items change.

Syntax

browser.storage.onChanged.addListener(callback)
browser.storage.onChanged.removeListener(listener)
browser.storage.onChanged.hasListener(listener)

Events have three functions:

addListener(callback)

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

callback

Function that will be called when this event occurs. The function will be passed the following 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.

areaName

string. The name of the storage area ("sync", "local", or "managed") to which the changes were made.

Browser compatibility

Examples

/*
Log the storage area that changed,
then for each item changed,
log its old value and its new value.
*/
function logStorageChange(changes, area) {
  console.log("Change in storage area: " + area);

  let changedItems = Object.keys(changes);

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

browser.storage.onChanged.addListener(logStorageChange);

Example extensions

• proxy-blocker