Yesterday I compressed 5 files which take up most of the bandwidth
59Kb map.js
32Kb geometry.js
30Kb wz_jsgraphics.js
7Kb map_obj.js
6Kb point.js
totalling 131Kb of client side scripts.
Compressing with Shrinksafe resulted in a total of 66.5Kb, while JSMin
reduced the size to 74.2Kb.
Unfortunately, two issues arise with compression:
1) I encountered some evil eval code in Mapbender: there are register
functions that look like this
"functionName(parameterName)"
If we pack the files with Shrinksafe, the variable in the scope, where
the register function is evaluated
eval(mb_MapRequestSubFunctions[i]);
is no longer named "parameterName" but "_55". So JS throws an
exception like "unknown variable parameterName".
There are two possible solutions: use JSMin, or find a way to run
Shrinksafe in a way that variable names are not shortened. But then the
compression advantage of Shrinksafe compared to JSMin might vanish and
it might not make a difference which one to use.
2) Using JSMin, Firefox crashes randomly when the Firebug plugin is
enabled and "Net" is selected. I believe it is a Firebug bug. In IE
Mapbender loads without problems.
I propose we use JSMin for the upcoming release; but I would be happy to
discuss other solutions for the future.
But with about 57Kb we still have saved a considerable amount of
bandwidth.
Christoph
Christoph Baudson (WhereGroup) schrieb:
thanks for your suggestion, Marc.
I have checked the tool and the compression rates are better than JSMin's.
While JSMin compressed my sample file (map.js, around 60K) to 70%,
Shrinksafe made it to around 60%. I think I will try to compress the
relevant files with both and want to see if there is a difference. If
not, then Shrinksafe is definitely a good choice.
I have also found a nice online interface at
http://alex.dojotoolkit.org/shrinksafe/
The next step would be to find an easy way of compressing all the
relevant files in one go, preferably via Eclipse's "Export", as Uli
suggested. How do we proceed? I have created a ticket at
http://trac.osgeo.org/mapbender/ticket/54
Christoph
Marc Jansen schrieb:
Hi list,
I would love to see compression brought to the Javascript files and
have another suggestion as for the compression tool:
http://dojotoolkit.org/docs/shrinksafe (a nice article which shows how
to use the compression tool)
The Java-file custom_rhino.jar is used to pack Javascript. This is
used within the dojotoolkit (www.dojotoolkit.org) for example. One can
download the file here:
http://svn.dojotoolkit.org/dojo/trunk/buildscripts/lib/custom_rhino.jar
-- Marc
Christoph Baudson (WhereGroup) schrieb:
To enable Mapbender to load faster, the new release will employ
JavaScript compression.
There has been a lot of discussion about this in the past; I think
packing the JS files with JSMin is the best idea:
http://www.crockford.com/javascript/jsmin.html
+ the existing JS code must not stick to a given syntax
+ transparent (removes only linefeeds, whitespaces and comments)
+ no obfuscation
0 compared to real packers with still a good compression rate.
Files that are already compressed with other packers (like jQuery)
will of course not be re-compressed.
Some more questions arise:
1) Where to store the compressed/uncompressed files in the file
system. The default setting should be "compressed" IMHO. It should be
easy to switch back and forth from uncompressed to compressed.
2) Which settings? Take a look at
http://fmarcia.info/jsmin/test.html
You can add comments. The compressed JS files will not have a license
on top of the script, as comments are removed. Do we have to add a
license?
For compression settings, I chose "conservative" for my test run;
Some scripts like jsTree.js don't use the ; to end statements, so a
linefeed mustn't be removed.
Any ideas?
Christoph
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