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The simple-prefs module lets you 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.

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?"
    }]
}

Setting Attributes

Mandatory Common Attributes

These are attributes that all settings must have.

Attribute Description
type The type of setting, as defined in the "Setting Types" section below.
name

An identifier for the setting. This is used to access the setting 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 setting in the Add-ons Manager user interface.

Optional Common Attributes

These are attributes that all settings may have:

Attribute Description
description This appears below the setting title in the Add-ons Manager UI.
value A default value for the setting. Depending on the setting type, this may be an integer, string, or boolean value.
hidden

A boolean value which, if present and set to true, means that the setting won't appear in the Add-ons Manager interface, so users of your add-on won't be able to see or alter it.

{
    "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.

Setting-Specific Attributes

These are settings that are only applicable to certain setting types.
They are documented along with the
setting types themselves.

Setting Types

The setting types map to the
inline settings types
used by the Add-on Manager. All the inline settings 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 true or false, the "on" or "off" checkbox states are mapped to integers using "on" or "off" properties in the specification.

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 on() function for this preference is called.

This type requires an 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.

<api name="prefs">
@property {object}
experimental A persistent object private to your add-on. Properties with boolean,
number, and string values will be persisted in the Mozilla preferences system.
</api>

<api name="on">
@function
experimental Registers an event listener that will be called when a preference is changed.

Example:

function onPrefChange(prefName) {
    console.log("The " + prefName + " preference 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);

@param prefName {String}
The name of the preference to watch for changes.
@param listener {Function}
The listener function that processes the event.
</api>

<api name="removeListener">
@function
experimental Unregisters an event listener for the specified preference.

@param prefName {String}
The name of the preference to watch for changes.
@param listener {Function}
The listener function that processes the event.
</api>

Using the Preferences Service to Access Simple Prefs

If you ever need to access your simple-prefs with the preferences/service module,
you can do so using the extended preference name. To get this
just prepend "extensions." + require("sdk/self").id + "." to the preference name "somePreference".

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']

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