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Listen to changes to the Preferences system in Firefox. This enables add-ons to listen to change events to the system-wide settings. These are the same preferences that are exposed to users in the about:config page.
preferences/service gives you full access to the preferences system. You can also use the simple-prefs module to access just the preferences for your own add-on and expose them to the user in the Add-on Manager.





options : object
Required options:

Name Type  
branchName string

By default this is "", the root.


var { PrefsTarget } = require("sdk/preferences/event-target");

// listen to the same branch which reqire("sdk/simple-prefs") does
var target = PrefsTarget({ branchName: "extensions." + require("sdk/self").preferencesBranch + "." });

target.once("test", function(prefName) {
  console.log(prefName) // logs "test"
  console.log(target.prefs[name]) // logs true

target.once("", function() {
  console.log(prefName) // logs "test"
  console.log(target.prefs[name]) // logs true

// changing a pref which our target listens to
require("sdk/simple-prefs").prefs.test = true;

Document Tags and Contributors

 Contributors to this page: wbamberg, evold
 Last updated by: wbamberg,