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Re: What Does This Code Do?

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[This follow-up accidentally went out as an e-mail at first; please ignore 
that.]

Gene Wirchenko wrote:

>      I suspect that this code was run through a compresser of some
> sort.  ("3e3" to save a byte over "3000" and the like.)  I can
> understand bits of it, but I can not parse it in total.

This source code was generated by a tool called a “minifier”, which you can 
deduce from observing that all variable and parameter identifiers are only 
one character long where the characters have successive Unicode code points 
(“a”, “b”, “c”, “d”, …).

Presumably you have seen this source code in a Web browser.  If so, and you 
have seen it in a script resource (usually with suffix “.js”) as well, you 
can use the *built-in* developer tools’ “pretty print” feature to make the 
source code easier readable.

For example, in Chrome Dev Tools it is toggled with the “{}” icon in the 
left bottom corner of the source code pane of the “Sources” tab; in 
Firefox/Iceweasel it is available as “Auto Prettify Minified Sources” in 
the Settings menu of the source code pane, and as “Prettify Sources” in its 
context menu, of the Web Developer Tools (not to be confused with the Web 
Developer extension [0a]).  Firebug 2.0.x [0b] also has the “{}” button; as 
a point of note, it also has a “Pretty Print” Command in the Command Editor 
of the Console (triangle buttons) that works if block braces were used, and 
a “Copy” button that is suited to create (non-minified) one-line code for 
bookmarklets out of the code in the Command Editor.

See also <http://devtoolsecrets.com/> (referred to by the FAQ in the 
section “Debugging”), section “Debugging Minified JavaScript” there.
 
As indicated, you can then use an editor that supports ECMAScript 
implementations insofar as that it can refactor a symbol in context to make 
the source code even easier to understand.  Eclipse JSDT [1] is one such 
editor (Ctrl+1 → “Rename in file”, or Ctrl+2 → R by default), Visual Studio 
Code (which is available even for Linux, and looks like a Sublime/Atom 
clone ;-)) is another; Atom can do it with the js-refactor package, and 
Sublime Text with Multiple Selections (built-in).

[0a] <http://chrispederick.com/work/web-developer/>
[0b] <http://getfirebug.com/>
[1]  <https://www.eclipse.org/webtools/jsdt/> pp.
[2]  <https://www.visualstudio.com/>
[3]  <https://atom.io/>
[4]  <http://www.sublimetext.com/>

-- 
PointedEars
FAQ: <http://PointedEars.de/faq> | SVN: <http://PointedEars.de/wsvn/>
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What Does This Code Do? Gene Wirchenko <genew@telus.net> - 2015-12-09 10:44 -0800
  Re: What Does This Code Do? Joao Rodrigues <groups_jr-1@yahoo.com.br> - 2015-12-09 18:17 -0200
  Re: What Does This Code Do? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-12-10 00:31 +0100

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