Experimental
Store preferences across application restarts. You can store booleans, integers, and string values, and users can configure these preferences in the Add-ons Manager. This gives users a consistent way to access and modify preferences across different add-ons.
This API is for your add-on's preferences. If you need to get and set the general browser preferences, use preferences/service.
Usage
Defining and initializing preferences
To define preferences and give them initial values, add a new JSON array called preferences
to your package.json file, and give it one entry for each preference:
{ "fullName": "Example Add-on", ... "preferences": [{ "name": "somePreference", "title": "Some preference title", "description": "Some short description for the preference", "type": "string", "value": "this is the default string value" }, { "description": "How many of them we have.", "name": "myInteger", "type": "integer", "value": 8, "title": "How Many?" }] }
Each preference is defined by a group of attributes. There are:
- mandatory attributes that all preferences must have
- optional attributes
- attributes that are specific to the preference's data type
Mandatory Common Attributes
These are attributes that all preferences must have.
Attribute | Description |
---|---|
type |
The type of preference, as defined in the "Preference Types" section below. |
name |
An identifier for the preference. This is used to access the preference from your add-on: console.log(require("sdk/simple-prefs").prefs.mySettingName); This means that it must be a valid JavaScript identifier. |
title |
This is used as a label for the preference in the Add-ons Manager user interface. |
Optional Common Attributes
These are attributes that all preferences may have:
Attribute | Description |
---|---|
description |
This appears below the preference title in the Add-ons Manager UI. |
value |
A default value for the preference. Depending on the preference type, this may be an integer, string, or boolean value. |
hidden |
A Boolean value which, if present and set to { "name": "myHiddenInteger", "type": "integer", "title": "How Many?", "hidden": true } Your add-on's code will still be able to access and modify it, just like any other preference you define. |
Type-Specific Attributes
These are settings that are only applicable to certain preference types. They are documented along with the preference types themselves.
Preference Types
The setting types map to the inline settings types used by the Add-on Manager. All the inline preferences are supported.
Type | Description | Example Specification |
---|---|---|
bool |
Displayed as a checkbox and stores a boolean. |
{ "description": "Does it have tentacles?", "type": "bool", "name": "hasTentacles", "value": true, "title": "Tentacles" } |
boolint |
Displayed as a checkbox and stores an integer. A boolint is presented to the user as a checkbox, but instead of storing To provide this mapping the boolint requires two mandatory attributes called "on" and "off", both of which are supplied as strings. Note that even so, the "value" property is supplied as an integer. |
{ "type": "boolint", "name": "myBoolint", "on": "1", "off": "2", "value": 1, "title": "My Boolint" } |
integer |
Displayed as a textbox and stores an integer. |
{ "description": "How many eyes?", "type": "integer", "name": "eyeCount", "value": 8, "title": "Eye count" } |
string |
Displayed as a textbox and stores a string. |
{ "type": "string", "name": "monsterName", "value": "Kraken", "title": "Monster name" } |
color |
Displayed as a colorpicker and stores a string in the #123456 format. |
{ "type": "color", "name": "highlightColor", "value": "#6a5acd", "title": "Highlight color" } |
file |
Displayed as a "Browse" button that opens a file picker and stores the full path and name of the file selected. |
{ "type": "file", "name": "myFile", "title": "Select a file" } |
directory |
Displayed as a "Browse" button that opens a directory picker and stores the full path and name of the directory selected. |
{ "type": "directory", "name": "myDirectory", "title": "Select a directory" } |
menulist |
Displayed as a drop-down list. The type of the stored value depends on the default value. The options are specified by a mandatory "options" attribute, that is an array of objects with mandatory attributes "label" and "value"
The values of the "value" attributes must be supplied as strings. The values of the "label" attributes prefixed with "{name}_options.", where {name} is the name of the preference, are used as localization keys. If no matching entries are found, the value of the "label" attributes is used verbatim as labels. |
{ "name": "typeOfBreath", "type": "menulist", "title": "Type of breath", "value": 0, "options": [ { "value": "0", "label": "Fire" }, { "value": "1", "label": "Cold" }, { "value": "2", "label": "Disintegration" } ] } |
radio |
Displayed as radio buttons. The type of the stored value depends on the default value. The options are specified by a mandatory "options" attribute, that is an array of objects with mandatory attributes "label" and "value"
The values of the "value" attributes must be supplied as strings. The values of the "label" attributes prefixed with "{name}_options.", where {name} is the name of the preference, are used as localization keys. If no matching entries are found, the value of the "label" attributes is used verbatim as labels. |
{ "name": "alignment", "type": "radio", "title": "Alignment", "value": "N", "options": [ { "value": "L", "label": "Lawful" }, { "value": "N", "label": "Neutral" }, { "value": "C", "label": "Chaotic" } ] } |
control |
Displays a button. When the user clicks the button, the function listening to the This type requires a mandatory attribute called "label" which is provided as a string. It is used to label the button. |
In "package.json": { "type": "control", "label": "Click me!", "name": "sayHello", "title": "Say Hello" } In "main.js": var sp = require("sdk/simple-prefs"); sp.on("sayHello", function() { console.log("hello"); }); |
Localization
Using the SDK's localization system, you can provide translated forms of the title
and description
attributes. See the localization tutorial for more details.
Getting and setting preferences
Unless you've marked them as hidden
, the user will be able to see and change the preferences in the Add-on Manager.
You can also see them and change them programmatically using the prefs
property, and listen for changes to a preference using on()
.
Simple-prefs in the preferences system
Preferences defined using simple-prefs are stored in the Firefox preferences system alongside all the other preferences. This means that they're visible in about:config, and they can be accessed using the global simple-preferences
module. By default, simple preferences are stored in a preference like:
extensions.<addon-id>.<preference-name>
For example, if you had a simple-pref named "somePreference"
then you could get its value like so:
require('sdk/preferences/service').get(['extensions', require('sdk/self').id, 'somePreference'].join('.'))
This would give you the same value as:
require('sdk/simple-prefs').prefs['somePreference']
The ability to change the default preferences branch is new in Add-on SDK 1.15.
The branch of the preferences tree under which simple-prefs are stored is, by default, the add-on ID. Sometimes you might need to use a different branch, especially if you are porting an add-on to the SDK. You can change the sub-branch of extensions
using the preferences-branch
key in your add-on's package.json file.
Globals
Functions
on(prefName, listener)
Registers an event listener
that will be called when a preference is changed.
The event listener may take an optional parameter that specifies the name of the property which changed.
Preference change events are triggered for every character typed by the user. They are also triggered once during add-on initialization.
Example:
function onPrefChange(prefName) { console.log("The preference " + prefName + " value has changed!"); } require("sdk/simple-prefs").on("somePreference", onPrefChange); require("sdk/simple-prefs").on("someOtherPreference", onPrefChange); // `""` listens to all changes in the extension's branch require("sdk/simple-prefs").on("", onPrefChange);
Parameters
prefName : String
The name of the preference to watch for changes.
listener : Function
The listener function that processes the event.
removeListener(prefName, listener)
Unregisters an event listener
for the specified preference.
Parameters
prefName : String
The name of the preference to watch for changes.
listener : Function
The listener function that processes the event.
Properties
prefs
This property is an object containing the simple-prefs you have defined for your add-on. You can use it to access preference values and to change them. Suppose you've defined a preference like this:
"preferences": [{ "name": "somePreference", "title": "Some preference title", "description": "Some short description for the preference", "type": "string", "value": "this is the default string value" }]
You can access somePreference
using the prefs
property:
var preferences = require("sdk/simple-prefs").prefs; console.log(preferences.somePreference); preferences.somePreference = "this is a new value"; console.log(prefs["somePreference"]); // bracket notation preferences["somePreference"] = "this is the default string value";
console.log: my-addon: this is the default string value console.log: my-addon: this is a new value