CS242

SpiderMonkey JavaScript Shell

SpiderMonkey is the JavaScript engine used in Firefox 2.0. On this page, you can download the SpiderMonkey engine as a stand-alone JavaScript shell.

Download SpiderMonkey for Windows:

To download the JavaScript shell, download the SpiderMonkey executable and the Cygwin DLL to the same folder.

• SpiderMonkey executable
• Cygwin DLL

Download SpiderMonkey for Mac OS X:

To download the JavaScript shell, download the SpiderMonkey zip file and extract the executable.

• SpiderMonkey zip file

Example Usage:

To run the shell, double-click js.exe. If you see the error message "This application has failed to start because cygwin1.dll was not found.", be sure the Cygwin DLL is in the same folder as js.exe. You should now see the following prompt:

js> 

js> function f(x) { return x + 5; }
js> f(7);
12
js> function curriedAdd(x) { return function(y) { return x + y; } }
js> var h = curriedAdd(3);
js> h(4);
7
js> quit();

Useful Built-in Functions:

The SpiderMonkey shell has a number of useful built-in functions. The function help(); prints a list. Listed below are a few that are particularly instructive:

Command        Usage                  Description
=======        =====                  ===========
print          print([exp ...])       Evaluate and print expressions
help           help([name ...])       Display usage and help messages
quit           quit()                 Quit the shell
dis            dis([fun])             Disassemble functions into bytecodes
dissrc         dissrc([fun])          Disassemble functions with source