Code snippets

This is a quick list of useful code snippets (small code samples) available for developers of extensions for the various Mozilla applications. Many of these samples can also be used in XULRunner applications, as well as in actual Mozilla code itself.

These examples demonstrate how to accomplish basic tasks that might not be immediately obvious.


Examples and demos from MDN articles
A collection of examples and demos from articles.
Window code
Opening and manipulating windows
Toolbar related code
Sidebar related code
Forms related code
Code used to parse, write, manipulate, etc. XML
File I/O
Code used to read, write and process files
Drag & Drop
Code used to setup and handle drag and drop events
Code used to display and process dialog boxes
Alerts and Notifications
Modal and non-modal ways to notify users
Code used to read, write, and modify preferences
Code used to define and call XPCOM components in JavaScript
Running applications
Code used to run other applications
<canvas> related
WHAT WG Canvas-related code
Signing a XPI
How to sign an XPI with PKI
Delayed Execution
Performing background operations.
Miscellaneous useful code fragments
Using a hidden browser element to parse HTML to a window's DOM

JavaScript libraries

Here are some JavaScript libraries that may come in handy.

A library that implements a StringView view for JavaScript typed arrays. This lets you access data in typed arrays using C-like string functions.
By default, the only possible standardized scripting language for HTML is ECMAScript. Hence, if you are going to use another scripting language you might expect that most of the browsers will not recognize it. Nevertheless, the increasing computational power of modern browsers together with the introduction of typed arrays in ECMAScript allow us, in theory, to build full virtual machines in pure ECMAScript. Therefore, it is also possible, in theory, to use ECMAScript for a smaller task: parsing exotic programming languages (i.e., creating compilers). This snippets shows a possible way to start from.

Browser-oriented code

Tabbed browser code (Firefox/SeaMonkey)
Basic operations, such as page loading, with the tabbed browser, which is the heart of Mozilla's browser applications
Reading, writing, modifying, and removing cookies
Page Loading
Code used to load pages, reload pages, and listen for page loads
Interaction between privileged and non-privileged code
How to communicate from extensions to websites and vice-versa.
Downloading Files
Code to download files, images, and to monitor download progress
Password Manager
Code used to read and write passwords to/from the integrated password manager
Code used to read and write bookmarks
JavaScript Debugger Service
Code used to interact with the JavaScript Debugger Service


General information and utilities
SVG Animation
Animate SVG using JavaScript and SMIL
SVG Interacting with Script
Using JavaScript and DOM events to create interactive SVG
Embedding SVG in HTML and XUL
Using SVG to enhance HTML or XUL based markup

XUL Widgets

HTML in XUL for Rich Tooltips
Dynamically embed HTML into a XUL element to attain markup in a tooltip
Label and description
Special uses and line breaking examples
Setup and manipulation of trees using XUL and JS
Changing style of scrollbars. Applies to scrollbars in browser and iframe as well.
Code used to enable form autocomplete in a browser
Tips and tricks when using boxes as containers
Removing and manipulating tabs in a tabbox


Finding Window Handles (HWND) (Firefox)
How to use Windows API calls to find various kinds of Mozilla window handles. Window handles can be used for IPC and Accessibility purposes.
Using the Windows Registry with XPCOM
How to read, write, modify, delete, enumerate, and watch registry keys and values.

The content at MozillaZine Example Code is slowly being moved here, but you can still find useful examples there for now.