Minimizing Javascript and CSS in Eclipse

Websites need to load as quickly as possible. The results of Internet connections being faster and faster is that we can’t stand anymore waiting for a page to load. We’re used to speed and if the page doesn’t load, I’ll just close the tab and go somewhere else.

Minimizing is the process of reducing the size of CSS and JavaScript files by compressing it. This is achieved by removing unnecessary white spaces and newlines and also by renaming JavaScript variables to something shorter. With this technique I’ve managed to reduce the size of some JS files by 50%. Yahoo! provides a wonderful tool called YUICompressor that does the job for you.

I’ve been looking for a way to automatically minimize JS and CSS files upon save in Eclipse in my PHP projects… finally found out how to do it!

The idea is to edit .src.js and .src.css files. When saving the file, Eclipse will minimize it and create or update the corresponding .js or .css file using YUICompressor. So you will be editing the .src.js or .src.css file while of course, your website uses the .js or .css files. Note that I’m using Eclipse PDT.

We simply need a shell script (Mac OS or Linux) or Batch script (Windows) that minifies the file. Here’s the Mac OS / Linux shell script:

# minifies js and css files
# by Nicolas DEBARNOT
if [ -f $1 ]
 file=`echo $1 | sed 's/\.src//'`
 java -jar yuicompressor-2.4.2.jar $1 -o $file --charset utf-8 --nomunge

And the Windows batch script:

@echo off
set inputfile=%1
set outputfile=%inputfile:.src=%
java -jar yuicompressor-2.4.2.jar %inputfile% -o %outputfile% --charset utf-8 --nomunge

In Eclipse, open project properties, add a new builder, put under “location” the path to the minimizer script. Working directory should contain the yuucompressor-2.4.2.jar file and give it as argument the current resource using Eclipse’s variables: ${resource_loc}.

Make sure that “The selected resource” is checked in the “Refresh tab” and that “During auto builds” is checked in the “Build Options” tab.

Save your new builder and make sure that “Build Automatically” is checked in the “Project” menu and voilà!

10 thoughts on “Minimizing Javascript and CSS in Eclipse

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  4. Tom Jenkins

    Hi there

    This is brilliant and I am trying to implement it. I have it kind of working to a point but I wonder if you could help me further?

    I only want this to run when saving down .js and .css files? I use a coldfusion environment and when i try and save .cfm page, this build script tries to fire and errors.

    Also my files are named things like site.js or admin.js … and I would like the compressed files to be named site.min.js or admin.min.js … basically anything {filename}.min.js. How would I modify the script for this?

    Thank you for any help you can give

    Many thanks

    Tom Jenkins

  5. emolah

    Nice one. Saves so many time. Thanks a lot 🙂
    @Tom Jenkins: If you want the files to be named like min.js try this small script modification:

    @echo off
    set inputfile=%1
    set outputfile=%inputfile:.src=.min%
    java -jar yuicompressor-2.4.2.jar %inputfile% -o %outputfile% --charset utf-8 --preserve-semi

  6. emolah

    Does anybody know, if there is a possibility to make this project specific build configuration as a default configuration for web and/or php projects in Eclipse IDE?

  7. Nicolas Post author

    Hi, thanks emolah for answering Tom Jenkins quicker than me 😉

    Regarding making this a default configuration for similar projects in Eclipse, I’m not sure that’s possible. I’ll keep you posted if I find a way to do it though!

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