JavaScript Shell Extended

A command-line interface for JavaScript and DOM.

Open the shell or get the Shell bookmarklet.

Features

• You can enter statements and expressions at the same prompt.
• All code is evaluated under the latest JavaScript version supported by the browser.
• The result of each non-void statement or expression is shown.
• User-defined variables.
  • b = document.body
• User-defined functions.
  • function f() { return 5; } or function f() 5; in JavaScript 1.8
• JavaScript error messages are shown in red.
• Previous statements and expressions are available through Up and Down arrow keys.
• Tab completion.
• Multiline input (Shift+Enter to insert a line break).
• If the shell is opened using a bookmarklet, JavaScript typed into the shell runs in the context of the original window.
• Shell.JavaScript_version is set to the highest explicitly defined JavaScript version supported.
• If no native support for JSON is detected, loads a YUI compressed and packed version of json2.js
• Works well in Firefox, Opera 9 (which will give an annoyingly huge error backtrace), and Safari. I need testers for other browsers. Contact me if you want to be a tester.

Built-in functions

Please note: Hotkeys (the "Alt+Key" codes) may also require you to push the Shift key on Linux.

• ans: the result of the previous expression.
• print(expr): prints expr on its own line. If passed mutiple arguments, they will all be printed on one line as an array joined by ", "
  • for(i = 0; i < 6; ++i) print(i * i)
  • If the function, console.log is not already defined, all calls to console.log are forwarded to print
• pr(expr): prints and returns its input, so you can use it to print intermediate results in the middle of an expression.
  • function fact(n) { return n>0 ? pr(n*fact(n-1)) : 1 }
• load(scriptURI [, printLoadMessage [, forcedVersion]]): loads a JavaScript script. printLoadMessage and forcedVersion are optional. printLoadMessage defaults to true and determines if a loading message should be displayed. forcedVersion defaults to the current JavaScript version and determines the version of JavaScript a script should be run under.
  • load("http://example.com/foo.js", false, 1.8)
  • There are a quite a few libraries that you can load on the online version just by typing in their names in a load() call (case-sensitive) listed in a directory.
• blink(node) or Alt+B: makes a node blink for a second.
  • blink(document.links[3])
• props(obj) or Alt+P: lists the methods and fields of an object.
  • props(document.body)
  • In Firefox, props also shows which properties belong to the object itself and which belong to objects in its prototype chain.
• JSON.stringify(object) or Alt+J: creates a JSON representation of an object.
  • JSON.stringify({foo: "bar", id: 9814})
• JSON.parse(JSON string): parses a JSON string and returns an object.
  • JSON.parse('{"foo":"bar","id":9814}')

Suggested uses

• Test short bits of JavaScript, bookmarklets, or user scripts. (For longer bits of JavaScript, try the JavaScript development enviornment too.)
• Explore DOM objects such as document.body using props (Alt+P) to figure out what is possible.
• Explore the DOM of a specific page using the bookmarklet version of the shell.
• Modify the DOM of a specific page using the bookmarklet version of the shell.
• Use the shell like you would use the home screen of a calculator such as a TI-83. Alt+M gives you easy access to math functions such as sin and pow.

About

The JavaScript shell was created by Jesse Ruderman. Ted Mielczarek added the tab completion feature in 1.1, Edward Lee added the multiline input feature in 1.2, Jesper Rønn-Jensen fixed a few bugs for 1.4, and Elijah Grey added JSON support, enhanced print(), and latest JavaScript version evaling in 1.4 Extended. Changelogs for some versions are available. The JavaScript Shell is GPL/LGPL/MPL tri-licensed.

Last modified October 11, 2009.