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Tool to reverse Javascript minify? [duplicate]

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Are there any command line scripts and/or online tools that can reverse the effects of minification similar to how Tidy can clean up horrific HTML?
(I'm specifically looking to unminify a minified JavaScript file, so variable renaming might still be an issue.)

You can use this : http://jsbeautifier.org/
But it depends on the minify method you are using, this one only formats the code, it doesn't change variable names, nor uncompress base62 encoding.
edit: in fact it can unpack "packed" scripts (packed with Dean Edward's packer : http://dean.edwards.name/packer/)

Chrome developer tools has this feature built-in. Bring up the developer tools (pressing F12 is one way), in the Sources tab, the bottom left bar has a set of icons. The "{}" icon is "Pretty print" and does this conversion on demand.
UPDATE: IE9 "F12 developer tools" also has a "Format JavaScript" feature in the Script tab under the Tools icon there. (see Tip #4 in F12 The best kept web debugging secret)

Got it! JSBeautifier does exactly this, and you even have options for the auto-formatting.

Can't you just use a javascript formatter (http://javascript.about.com/library/blformat.htm) ?

In Firefox, SpiderMonkey and Rhino you can wrap any code into an anonymous function and call its toSource method, which will give you a nicely formatted source of the function.
toSource also strips comments.
E. g.:
(function () { /* Say hello. */ var x = 'Hello!'; print(x); }).toSource()
Will be converted to a string:
function () {
var x = "Hello!";
print(x);
}
P. S.: It's not an "online tool", but all questions about general beautifying techniques are closed as duplicates of this one.

If you have a Mac and TextMate - An easy alternative for formatting Javascript is:
Open the file with Textmate.
Click on > Bundles > JavaScript > Reformat Document
Crack open a beer.

Most of the IDEs also offer auto-formatting features. For example in NetBeans, just press CTRL+K.

As an alternative (since I didn't know about jsbeautifier.org until now), I have used a bookmarklet that reenabled the decode button in Dean Edward's Packer.
I found the instructions and bookmarklet here.
here is the bookmarklet (in case the site is down)
javascript:for%20(i=0;i<document.forms.length;++i)%20{for(j=0;j<document.forms[i].elements.length;++j){document.forms[i].elements[j].removeAttribute(%22readonly%22);document.forms[i].elements[j].removeAttribute(%22disabled%22);}}

I'm not sure if you need source code. There is a free online JavaScript formatter at http://www.blackbeltcoder.com/Resources/JSFormatter.aspx.

Try this one, with code coloration:
http://labs.swelen.com/tools/javascript/beauty.html

click on these link for JS deminification. That will install on FF as extension that help you in debugging js at runtime.
https://addons.mozilla.org/en-US/firefox/addon/javascript-deminifier/eula/141018?src=dp-btn-primary

Similar to Stone's answer, but for Windows/.NET developers:
If you have Visual Studio and ReSharper - An easy alternative for formatting Javascript is:
Open the file with Visual Studio;
Click on ReSharper > Tools > Cleanup Code (Ctrl+E, C);
Select "Default: Reformat code", and click OK;
Crack open a beer.

Despite its miles-away-from-being-pretty interface, JSPretty is a good, free and online tool for making javascript source codes human-readable. You can enforce your preferred type of indentation and it can also detect obfuscation.

If one is in JS possibility of using Firefox is more. And if its Firefox add on is for rescue. Following one is particularly useful.
https://addons.mozilla.org/en-US/firefox/addon/phoenix/

Pretty Diff will beautify (pretty print) JavaScript in a way that conforms to JSLint and JSHint white space algorithms.

Wasn't really happy with the output of jsbeautifier.org for what I was putting in, so I did some more searching and found this site: http://www.centralinternet.com.br/javascript-beautifier
Worked extremely well for me.

http://unminify.appspot.com/
Great tools for unminify javascript and json

IDE for JavaScript development [closed]

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What do you suggest for JS development IDE. Is there something similar to VisualStudio IDE, so I can run/debug my application in it?

At JetBrains we've just developed lightweight HTML/Javascript/CSS IDE WebStorm that includes very smart JavaScript Editor with DOM-based autocompletion and HTML5 API support.
It allows you to debug(breakpoints supported) and run your scripts directly from IDE.

A few options:
Visual Studio 2008 (including VWD Express, http://blog.berniesumption.com/software/how-to-debug-javascript-in-internet-explorer/)
Adobe Dreamweaver CS4
Notepad++ (or any other text editor), Firefox and Firebug

I think IntellJ's JavaScript support is excellent, just like everything else that they do.

Netbeans 6.x and Firefox+Firebug
In the past I used Aptana Standalone or as a Eclipse plugin. The Pro version has some nice addons like the embedded IE (to the always embedded Firefox) and debugging support for both browsers.
I found after hours of testing, that Suns Netbeans is the best PHP and Python IDE for Windows and Linux. I was surprised that also Javascript support can hold the candle to Aptana.
So Netbeans is my recommendation (not only for Javascript).
Give it a try, its free!

I've found Aptana Studio to be good.

I tend to recommend more and more Netbeans that has not been proposed yet (I am blind sometimes). Netbeans is developed by Sun and support not only Java but also a few other languages (PHP,Ruby,Python, Javascript).
I use it for a while now and I am very satisfied. It is fast, provides code completion and integrates easily major JS libraries (Prototype, YUI). It has also a debugger that you can tied to FF or IE.
Try it you won't be disappointed!

Here's a good list of IDEs you can use for writing JavaScript:
http://www.programmerfish.com/top-8-ide-integrated-development-environment-for-java-script-html5-ajax/

Nowadays I am using JetBrains' PHPStorm and I can easily say, this is the best editor I've ever tried. Comes with lots of features that I have not seen at other editors like,
find a word in a directory (grep equivalent)
extended and useful intellisense feature with multiple files and parent classes
internal GIT support
a tree view for application structure
an awesome version history support that works with GIT and your local history. This is very useful when you want to take a look at a GIT untracked file, you can see all history details of the file for weeks.
with a great addon named CSSXFire that works with Firebug and tracks the CSS changes and import them to editor and allows you easily reproduce the same changes that you've done in Firebug CSS Console. This is really awesome
another useful feature is, when you want to delete or rename a file, editor searches the file has been used in this directory and notifies you. This is called safe-refactor
intellisense for files, while you typing a css background-image, a src or an href attribute
Sometimes I deal with PHP so I prefer PHPStorm, so Front End Developers should prefer WebStrorm that is specialized for us.
I think, every FE Developer should try PHPStorm or WebStorm with Firefox and Firebug.

Komodo IDE (or the free Komodo Edit if you can live without an integrated debugger) are pretty nice.

I tried few IDE last week and NetBeans is my winner. It got silent upload option for file upload in background. And very good code completion, folding, etc.

Here is my experience with the applications based on Extjs in UI with Java as server side language. I am a big supporter of open source technologies/products.
I so far I have used Eclipse, Netbeans, Webstorm and notepad++ with some added plugins.
And I feel Netbeans is best in terms of Syntax highlighting and formating. It recognizes missing commas, global variables, duplicate keys for object literals in a very impressive way.
Almost similar things can be achieved by adding some pligins like Spket in eclipse too, but it asks for licence when you go for advance level of settings.
If you are not so much concern about an integrated environment with web server then Web storm is best in all the aspects, but the biggest drawback of it is, "Its paid". ( Even if it asks for 1000 Rs ).

Firebug and a good syntax highlighting text editor is about the best combo. It's not necessary to add in much else. With just this combo you get:
Ability to set breakpoints
Inspect objects
Traverse the DOM
Alter CSS rules on the fly
See network traffic/responses
Evaluate and substitute code on the fly in production
And there are tools which add on to Firebug:
YSlow - Determine "why" your page is slow
Fireunit - Run unit tests
One of the advantage of Javascript development is that it's flexible and you can get instantaneous feedback while developing. I see no reason to get in the way of that by adding an IDE which includes a "deployment" step.

Notepad++ comes with built-in javascript syntax highlighting and JSlint plugin is very handy. IMHO for debugging there is nothing better than Chrome developer tools or Firebug.

This page reviews the most advanced Javascript IDEs (in terms of refactoring and intellisense anyway) :
http://blue-walrus.com/2013/08/review-javascript-ides/

Eclipse and JSEclipse plugin and of course Firefox + Firebug the ultimate duo. You'll find this development setup satisfactory.

Aptana is a great IDE as it will provide intelli-sense for CSS, javascript, html, java, etc. The debugger gives you the choice to run in FF or IE and is a full featured debugger. The community edition allows you to run a server side javascript as well. A very solid and feature rich platform for free.

Decent JavaScript IDE [closed]

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Closed 11 years ago.
What is a decent IDE for developing JavaScript, I'll be writing both client side stuff and writing for Rhino. Ideally It needs to run on Mac OSX, although something that runs on Windows too would be nice.
ADDITIONAL:
Having had a play with both js2 and Aptana, I think I'll be continuing to use Aptana. Mainly because I find emacs a bit hard to get my head round, although I did think that the error hi-lighting in js2 was better than that in Aptana.
I'm still looking for a way to visually debug my js code that is running atop Rhino...

Aptana IDE, absolutely. Stable, great syntax support for all the major javascript libraries, very good css and html editors. Also good support for php, air, ruby on rails and iPhone app development (I never tested this one).
Aptana can also connect to remote site via ftp (sftp in the pro edition) and to svn and cvs repositories.
It's based on Eclipse, so it's not exactly a lightweight application. But it's really, really good. You can also use it as an Eclipse plugin if you develop java wab app, but when I tested it in this version, about 1 year ago, it was not stable. Much better to use the standalone version.

If you're familiar with Emacs Steve Yegge's js2-mode could be worth a look.

Aptana Studio, both standalone and Eclipse plugin versions were quite ok last time I used them.

I have found the Spket Eclipse plugin very useful.

Take a look at WebStorm HTML/JavaScript Editor. It's lightweight and runs on MacOS. It supports debugging and running your code right from IDE and has very smart autocompletion capabilities for JavaScript both DOM-based and browser-based.

Komodo Edit/IDE is definitely the best IDE/editor (that I have used) for developing JavaScript.
Notable features include live error reporting, JavaScript macros and syntax auto-complete for ALL major frameworks!

If you have a very big application written in Javascript, there's only IntelliJ Idea. It parses multiple Javascript files and highlights not only syntax errors but undeclared variables and functions, allows to jump from function call to function definition, and more.
I've tried Emacs (because that's my favorite editor) and Komodo, and they don't come close. I guess it's the same for Eclipse.
Personally, I think that superior parsing and navigation abilties of Idea are only required when you're working with crappy undocumented code, otherwise I'd happily write the code in Emacs using js2-mode, but I'm working with huge poorly documented and buggy framework and it really helps to be able to jump to the source of the function or superclass to check how they work.

Are there any JavaScript static analysis tools? [closed]

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I'm used to having my compiler complain when I do something stupid like a typo on a variable name but JavaScript has a habit of letting this pass.
Are there any static analysis tools for JavaScript?

UPDATED ANSWER, 2017: Yes. Use ESLint. http://eslint.org
In addition to JSLint (already mentioned in Flash Sheridan's answer) and the Closure compiler (previously mentioned in awhyte's answer) I have have also gotten a lot of benefit from running JSHint and PHP CodeSniffer. As of 2012, all four tools are free open-source and have a large and active developer community behind them. They're each a bit different (and I think, complementary) in the kinds of checks they perform:
JSLint was designed to be, and still is Douglas Crockford's personal linting tool. It ships with a great default ruleset -- Crockford's own, constantly updated as he continues to learn about JavaScript and its pitfalls. JSLint is highly opinionated and this is generally seen as a good thing. Thus there's (intentionally) a limited amount you can do to configure or disable individual rules. But this can make it tough to apply JSLint to legacy code.
JSHint is very similar to JSLint (in fact it began life as JSLint fork) but it is easier/possible to configure or disable all of JSLint's checks via command line options or via a .jshintrc file.
I particularly like that I can tell JSHint to report all of the errors in a file, even if there are hundreds of errors. By contrast, although JSLint does have a maxerr configuration option, it will generally bail out relatively early when attempting to process files that contain large numbers of errors.
The Closure compiler is extremely useful in that, if code won't compile with Closure, you can feel very certain said code is deeply hosed in some fundamental way. Closure compilation is possibly the closest thing that there is in the JS world to an "interpreter" syntax check like php -l or ruby -c
Closure also warns you about potential issues such as missing parameters and undeclared or redefined variables. If you aren't seeing the warnings you expect, try increasing the warning level by invoking Closure with an option of --warning_level VERBOSE
PHP CodeSniffer can parse JavaScript as well as PHP and CSS. CodeSniffer ships with several different coding standards, (say phpcs -i to see them) which include many useful sniffs for JavaScript code including checks against inline control structures and superfluous whitespace.
Here is a list of JavaScript sniffs available in PHP CodeSniffer as of version 1.3.6 and here is a custom ruleset that would allow you to run them all at once. Using custom rulesets, it's easy to pick and choose the rules you want to apply. And you can even write your own sniffs if you want to enforce a particular "house style" that isn't supported out of the box. Afaik CodeSniffer is the only tool of the four mentioned here that supports customization and creation of new static analysis rules. One caveat though: CodeSniffer is also the slowest-running of any of the tools mentioned.

I agree that JSLint is the best place to start. Note that JavaScript Lint is distinct from JSLint. I’d also suggest checking out JSure, which in my limited testing did better than either of them, though with some rough edges in the implementation—the Intel Mac version crashed on startup for me, though the PowerPC version ran fine even on Intel, and the Linux version ran fine as well. (The developer, Berke Durak, said he'd get back to me when this was fixed, but I haven't heard from him.)
Don’t expect as much from JavaScript static analysis as you get from a good C checker. As Durak told me, “any non-trivial analysis is very difficult due to Javascript's dynamic nature.”
(Another, even more obscure Mac-only bug, this time with JSLint’s Konfabulator widget: Dragging a BBEdit document icon onto the widget moves the document to the trash. The developer, Douglas Crockford, hadn’t tried the widget on a Mac.)
10 August 2009: Today at the Static Analysis Symposium, Simon Holm Jensen presented a paper on TAJS: Type Analyzer for JavaScript, written with Anders Møller and Peter Thiemann. The paper doesn’t mention the above tools, but Jensen told me he’d looked at some of them and wasn’t impressed. The code for TAJS should be available sometime this summer.

Google's "Closure" JS compiler produces configurable warnings and errors at compile-time. It definitely finds misspelled variables and methods, plus arity mistakes. If you're willing to write JsDoc the Closure way, it can do a lot with type information, too.
The YUI "Compressor" tool can produce warnings too, but haven't tried it yet.
I haven't had much luck with the Aptana IDE, built on Eclipse, but other people like it. See Stack Overflow discussion of JS IDEs.
The IntelliJ IDE, which isn't free last I checked, has frickin' excellent JS support. It will detect and highlight misspelled vars and methods as you type, and more. It's got autocomplete, too.

In summary, JSLint, JSHint, Plato, ESLint, Google Closure-Linter are the tools available.
I faced installation issues while trying out Google Closure-Linter for Windows. But, it does mention on the web page that its support for Windows is experimental.
I found and tried another tool which works well. Here is the link for it:
http://esprima.org/
Also, this is the github link for the tool Esprima:
https://github.com/ariya/esprima

You can see some tools for JavaScript static code analysis in this Wiki.
A tool in the Wiki, but not mentioned in this post, is DeepScan.
Its focus is to find runtime errors and quality issues rather than coding conventions of linters. It covers also TypeScript, React and Vue.js.
You can try it out for your GitHub project.

I tried out ESlint and found it good..you can also add custom rules there..Here is the github repo: https://github.com/nzakas/eslint and here is the introduction to it: http://www.nczonline.net/blog/2013/07/16/introducing-eslint/

More security focused than general purpose list can be found on the Mozilla Wiki at Security/B2G/JavaScript code analysis
The purpose of this document is to collect JavaScript code analysis
tools suitable for including in coming Mozilla projects or for
internal use.
Also there is at least one commercial product that does security analysis: Burp gets new JavaScript analysis capabilities
The latest release of Burp includes a new engine for static analysis of JavaScript code. This enables Burp Scanner to report a range of new vulnerabilities, including:
DOM-based XSS
JavaScript injection
Client-side SQL injection
WebSocket hijacking
Local file path manipulation
DOM-based open redirection
Cookie manipulation
Ajax request header manipulation
DOM-based denial of service
Web message manipulation
HTML5 storage manipulation

In the commercial realm, Coverity Static Analysis supports analysis of JavaScript as of version 7.7 (mid-2015). Regarding your specific inquiry about typos, my pet project appearing in the latest release (8.0, beginning of 2016) does find typos in names of program elements.
As a key developer on the project, please accept my shameless plug: Though not yet as mature as the venerated C/C++ analysis, Coverity's JavaScript analysis shares much of the same engine, with the same focus on finding high-value defects with a low rate of false positive defect reports. We are increasing our focus on finding security defects in JavaScript (and other languages), in addition to finding general programming errors.
Now, here are some typos it finds (exact typo left as an exercise for the reader, to emphasize how easily these can be overlooked):
merge.js: (stable link) (latest revision)
commands-packages-query.js: (stable link) (latest revision)
series-pie-tests.js: (stable link) (latest revision)
outline_case.js: (stable link) (latest revision)

I like Jslint for this sort of thing...

Flow does static analysis with and without annotations.
If you need annotations, the syntax is compatible to TypeScript.
Install the package with :
npm install --global flow-bin
There's also some tooling. Have a look at gulp-flowtype and perhaps SublimeLinter-flow

JSAnalyse has just been published on codeplex.
It is a tool which analyses the dependencies between javascript files. You can even define the allowed dependencies and JSAnalysis checks whether the defined rules are fulfilled or not. That allows to keep track about the javascript dependencies even in big projects and have a clean architecture.
JSAnalyse can be executed as a command line tool or configured via the Visual Studio Layer Diagramm. It is also easy to integrate into the build. With gated check-ins you can keep the dependencies under control.
http://jsanalyse.codeplex.com/

Our SD ECMAScript CloneDR is a tool for finding exact and near-miss copies of duplicated code across large JavaScript source code bases.
It uses the language syntax to guide the detection, so it will find clones in spite of format changes, inserted/deleted comments, renamed variables and even some inserted/deleted statements.
The site has a sample CloneDR run on Google's Closure library.

Full disclosure, I'm behind this: http://www.toptensoftware.com/minime which does minification, obfuscation and a reasonable set of lint style checks.

Are there any JavaScript live syntax highlighters? [closed]

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I've found syntax highlighters that highlight pre-existing code, but I'd like to do it as you type with a WYSIWYG-style editor. I don't need auto-completed functions, just the highlighting.
As a follow-up question, what is the WYSIWYG editor that stackoverflow uses?
Edit: Thanks to the answer below, I found two that look like they might suit my needs:
EditArea and CodePress
EDIT: See this question also:
https://stackoverflow.com/questions/379185/free-syntax-highlighting-editor-control-in-javascript

The question might be better stated as "What syntax-highlighting editor do you recommended to replace an html textarea in my web app?" (Some of the other answers here deal with desktop apps or pure-syntax highlighters, not client-side editors)
I also recommend CodeMirror, it's written in Javascript and supports lots of browsers. It uses a real parser (rather than regexps) so it can deal with complex problems like correctly highlighting escaped strings. The developer is also very responsive on the discussion group.

Here is a really interesting article about how to write one: (Even better, he gives the full source to a JavaScript formatter and colorizer.)
Implementing a syntax-higlighting JavaScript editor in JavaScript
or
A brutal odyssey to the dark side of the DOM tree
How does one do decent syntax
highlighting? A very simple scanning
can tell the difference between
strings, comments, keywords, and other
code. But this time I wanted to
actually be able to recognize regular
expressions, so that I didn't have any
blatant incorrect behaviour anymore.
Importantly, it handles regex correctly. Also of interest is that he used a continuation passing style lexer/parser instead of the more typical lex (or regex) based lexers that you'll see in the wild.
As a bonus he discusses a lot of real-world issues you'll run into when working with JavaScript in the browser.

See Google code pretify.
See this question for the edit control that stackoverflow uses.

Sorry to drag this back up but the best i have found in CodeMirror http://codemirror.net/

I dont program a lot of javascript but JSEclipse has been pretty helpful for me in the past. It comes as an Eclipse plug-in.
I've been using it for years for free
http://www.interaktonline.com/products/eclipse/jseclipse/overview/
I also rely heavily on FireBug for Firefox whenever I deal with Javascript

You can also try http://softwaremaniacs.org/soft/highlight/en/ - it's fast, it supports not only javascript but many other languages. And if you need a live preview of how the highlighting will work, you can use setInterval to run the highlighting and show it in a separate box.

Although it has a steep learning curve, Vim is the best editor out there, for any language. It has a GUI version, but really shines in terminal editing. Any time spent learning how to use this editor is not time wasted. It has syntax highlighting, as you're looking for, as well as thousands (literally) of other features and plugins.

Gotta go with Bespin by Mozilla. It's built using HTML5 features (so it's quick and fast, but doesn't support legacy browsers though), but definitely amazing to use and beats everything I've come across - probably beacause it's Mozilla backing it, and they develop Firefox so yeah... There's also a jQuery Plugin which contains a extension for it to make it a bit easier to use with jQuery.