The `preferences/service` module provides access to the
application-wide preferences service singleton.
To define preferences for your own add-on and expose them to the user in
the [Add-on Manager](https://developer.mozilla.org/en-US/docs/Addons/Add-on_Manager),
you can use the [simple-prefs](modules/sdk/simple-prefs.html) module.
@function
Sets the application preference `name` to `value`.
@param name {string} Preference name.
@param value {string,number,boolean} Preference value.
**Example:**
var name = "extensions.checkCompatibility.nightly";
require("sdk/preferences/service").set(name, false);
@function
Gets the application preference `name`.
@param name {string}
@param defaultValue {string,number,boolean} Preference value.
@returns {string,number,boolean} Preference value, returns a default value if no
preference is set.
**Example:**
var name = "extensions.checkCompatibility.nightly";
var nightlyCompatChk = require("sdk/preferences/service").get(name);
@function
@param name {string} Preference name.
@returns {boolean} Returns whether or not the application preference `name` exists.
**Example:**
var name = "extensions.checkCompatibility.nightly";
if (require("sdk/preferences/service").has(name)) {
// ...
}
@function
@param root {string} Preference root name.
@returns {array} Returns an array of strings representing the child preferences of the root of this branch.
@function
@param name {string} Preference name.
@returns {boolean}
Returns whether or not the application preference `name` both exists
and has been set to a non-default value by the user (or a program
acting on the user's behalf).
**Example:**
var name = "extensions.checkCompatibility.nightly";
if (require("sdk/preferences/service").isSet(name)) {
// ...
}
@function
Clears a non-default, user-set value from the application preference
`name`. If no user-set value is defined on `name`, the function
does nothing. If no default value exists the preference will cease to exist.
@param name {string} Preference name.
**Example:**
var name = "extensions.checkCompatibility.nightly";
require("sdk/preferences/service").reset(name);
@function
Gets the localized value for an application preference `name`.
@param name {string}
@param defaultValue {string} Preference value.
@returns {string} Localized preference value, returns a default value if no
preference is set. Some preferences refer to a properties file.
So that `prefs.get` returns the properties file URL whereas
`prefs.getLocalized` returns the value defined in the properties file.
**Example:**
var prefs = require("sdk/preferences/service");
var name = "general.useragent.locale";
prefs.get(name); // is equal to "chrome://global/locale/intl.properties"
prefs.getLocalized(name) // is equal to "en-US"
@function
Sets the localized application preference `name` to `value`.
@param name {string} Preference name.
@param value {string} Preference value, a URL to a properties file
**Example:**
require("sdk/preferences/service").set("general.useragent.locale",
"chrome://global/locale/intl.properties");