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<!-- This Source Code Form is subject to the terms of the Mozilla Public
- License, v. 2.0. If a copy of the MPL was not distributed with this
- file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
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 ##
<span class="aside">
For more information on packaging, see the [Package Specification][] appendix.
</span>
The `packaging` global contains methods and metadata related to
the packages available in the current environment.
<code>packaging.**getURLForData**(*path*)</code>
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.
<code>memory.**track**(*object*, [*bin*])</code>
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`.
<code>memory.**getObjects**([*bin*])</code>
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:
<table>
<tr>
<td><code>weakref</code></td>
<td>A weak reference to the object being tracked. Call
<code>get()</code> on this object to retrieve its strong reference; if
a strong reference to the object no longer exists, <code>get()</code>
will return <code>null</code>.</td>
</tr>
<tr>
<td><code>created</code></td>
<td>A <code>Date</code> representing the date and time that
<code>memory.track()</code> was called on the object being
tracked.</td>
</tr>
<tr>
<td><code>filename</code></td>
<td>The name of the file that called <code>memory.track()</code> on
the object being tracked.</td>
</tr>
<tr>
<td><code>lineNo</code></td>
<td>The line number of the file that called
<code>memory.track()</code> on the object being tracked.</td>
</tr>
</table>
<code>memory.**getBins**()</code>
Returns an `Array` containing the names of all bins that aren't
currently empty.
[Package Specification]: dev-guide/package-spec.html
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