xpcshell

xpcshell is an XPConnect-enabled JavaScript Shell. It is a console application that lets you run JavaScript code. Unlike the ordinary JS shell (js), xpcshell lets the scripts running in it access XPCOM functionality.

Prerequisites

You need your own build of Mozilla to use xpcshell.

Running xpcshell

./run-mozilla.sh ./xpcshell

xpcshell is almost always in the same directory as run-mozilla.sh.

$ locate run-mozilla.sh
/usr/lib/firefox-0.10.1/run-mozilla.sh
/usr/lib/thunderbird-0.9/run-mozilla.sh
/usr/local/mozilla/run-mozilla.sh
/opt/mozilla/run-mozilla.sh
/root/.Trash/mozilla/run-mozilla.sh

Just pick one, cd over there, and run-mozilla.sh xpcshell, if it's present. (However, it might not be there if you have a non-debug version of Firefox, Mozilla, Thunderbird, etc.)

$ cd /opt/mozilla
$ ./run-mozilla.sh ./xpcshell
js> 

Using the Latest Version of Javascript

At present, xpcshell doesn't use the latest version of JavaScript, so newer language features, such as the let statement introduced in JavaScript 1.7, are not available. To rectify this, run xpcshell with the -v 180 command-line option, which tells xpcshell to use JavaScript 1.8.

Example

You can input JavaScript, straight to Mozilla.

js> 5+7
12
js> print("Hello, world!")
Hello, world!
js>

See also

• HOWTO for common problems in writing xpcshell scripts, e.g., doing async network calls or using JS modules.
• Pretty much all Mozilla programs use XPCOM components via XPConnect.
• Read XPConnect:Using components to get started with that.
• See the XPCShell Reference for information on command line arguments and extension functions.
• Learn how to write xpcshell-based unit tests.
• Read XPCShell:Profiling for information on how to profile scripts.