Parts of this page show the use of the XPInstall API. The majority of this API is now deprecated and as of Gecko 1.9 no longer available. Extension, Theme, and plug-in developers must switch away from install.js based packages to the new packaging scheme with an install.rdf manifest. In particular plugin developers should see how to package a plugin as an extension.
File
Use the File object to manipulate local files and directories during the installation process.
Overview
The File object has methods for analyzing the file system and preparing it (as when new directories, program shortcuts, version comparisons, or deletions are required) for newly installed software packages. The File object works in conjunction with the Install object.