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JavaScript code modules

JavaScript code modules let multiple privileged JavaScript scopes share code. For example, a module could be used by Firefox itself as well as by extensions, in order to avoid code duplication.

General topics

Using JavaScript code modules
An introduction to how to use JavaScript code modules.
Components.utils.import
How to import a JavaScript code module.
Components.utils.unload
How to unload a JavaScript code module.
Code snippets: Modules
Examples of how to use code modules.
Mozilla Labs JS Modules
This page features a list of JS modules, along with download links and documentation, that extension developers can use in their code.

Standard code modules

AddonManager.jsm
Interface to install, manage, and uninstall add-ons.
AddonRepository.jsm
Allows searching of the add-ons repository.
Assert.jsm
Implements the CommonJS Unit Testing specification version 1.1, which provides a basic, standardized interface for performing in-code logical assertions with optional, customizable error reporting.
ctypes.jsm
Provides an interface that allows JavaScript code to call native libraries without requiring the development of an XPCOM component.
CustomizableUI.jsm
Allows you to interact with customizable buttons and items in Firefox's main window UI.
DeferredTask.jsm
Run a task after a delay.
Dict.jsm
Provides an API for key/value pair dictionaries.
DownloadLastDir.jsm
Provides the path to the directory into which the last download occurred.
Downloads.jsm
Provides a single entry point to interact with the downloading capabilities of the platform.
FileUtils.jsm
Provides helpers for dealing with files.
Geometry.jsm
Provides routines for performing basic geometric operations on points and rectangles.
ISO8601DateUtils.jsm
Provides routines to convert between JavaScript Date objects and ISO 8601 date strings.
Log.jsm (formerly log4moz)
Provides a log4j style API for logging log messages to various endpoints, such as the Browser Console or a file on disk. This module was formerly
NetUtil.jsm
Provides helpful networking utility functions, including the ability to easily copy data from an input stream to an output stream asynchronously.
openLocationLastURL.jsm
Provides access to the last URL opened using the "Open Location" option in the File menu.
OSFile.jsm
Provides routines to access files. Read, write, rename, create directories, ...
PerfMeasurement.jsm
Provides access to low-level hardware and OS performance measurement tools.
PluralForm.jsm
Provides an easy way to get the correct plural forms for the current locale, as well as ways to localize to a specific plural rule.
PopupNotifications.jsm
Provides an easy way to present non-modal notifications to users.
Promise.jsm
Implements the Promises/A+ proposal as known in April 2013.
PromiseWorker.jsm
A version of ChromeWorker which uses promises to return the worker's result instead of using an event to do so.
Services.jsm
Provides getters for conveniently obtaining access to commonly-used services.
source-editor.jsm
The Source Editor is used by developer tools such as the Style Editor; this interface implements the editor and lets you interact with it.
Sqlite.jsm
A Promise-based API to mozIStorage/SQLite.
Task.jsm
Implements a subset of Task.js to make sequential, asynchronous operations simple, using the power of JavaScript's yield operator.
Timer.jsm
A pure JS implementation of window.setTimeout.
Webapps.jsm
Provides an interface to manager Open Web Apps.
WebRequest.jsm Requires Gecko 41.0
Provides an API to add event listeners for the various stages of making an HTTP request. The event listener receives detailed information about the request, and can modify or cancel the request.
XPCOMUtils.jsm
Contains utilities for JavaScript components loaded by the JS component loader.

Document Tags and Contributors

Last updated by: wbamberg,