Unstable
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.
Globals
Constructor
PrefsTarget(options)
Parameters
options : object
 Required options:
| Name | Type | |
|---|---|---|
| branchName | string | By default this is  | 
Example
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;