Globals in this section are subject to change in the future and/or are likely to be of interest to SDK module developers, rather than add-on developers. ## Components ## To access the infamous and powerful `Components` object, see the [Chrome Authority](dev-guide/tutorials/chrome.html) documentation. ## \_\_url\_\_ ## The `__url__` global is a string identifying the URL from which the code has been retrieved. If the code has no identifiable URL, this value may be `null`. ## packaging ## For more information on packaging, see the [Package Specification][] appendix. The `packaging` global contains methods and metadata related to the packages available in the current environment. packaging.**getURLForData**(*path*) Given a unix-style path relative to the calling package's `data` directory, returns an absolute URL to the file or directory. By "calling package", we mean the package in which the caller's source code resides. Thus, for example, if a package contains a resource at `data/mydata.dat` and a module at `lib/foo.js`, the module at `lib/foo.js` may make the following call to retrieve an absolute URL to `data/mydata.dat`: var myDataURL = packaging.getURLForData("/mydata.dat"); If the calling package has no `data` directory, an exception is thrown. ## memory ## `memory` is an object that exposes functionality to track objects of interest and help diagnose and prevent memory leaks. memory.**track**(*object*, [*bin*]) Marks *object* for being tracked, and categorizes it with the given bin name. If *bin* isn't specified, the memory tracker attempts to infer a bin name by first checking the object's `constructor.name`; if that fails or results in the generic `Object`, the stack is inspected and the name of the current function being executed—which is assumed to be a constructor function—is used. If that fails, then the object is placed in a bin named `generic`. memory.**getObjects**([*bin*]) Returns an `Array` containing information about tracked objects that have been categorized with the given bin name. If *bin* isn't provided, information about all live tracked objects are returned. Each element of the array is an object with the following keys:

weakref	A weak reference to the object being tracked. Call get() on this object to retrieve its strong reference; if a strong reference to the object no longer exists, get() will return null.
created	A Date representing the date and time that memory.track() was called on the object being tracked.
filename	The name of the file that called memory.track() on the object being tracked.
lineNo	The line number of the file that called memory.track() on the object being tracked.

memory.**getBins**() Returns an `Array` containing the names of all bins that aren't currently empty. [Package Specification]: dev-guide/package-spec.html