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Page optimizations done at the Rack level
Ruby JavaScript
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A Rack middleware for grouping Javascripts into one single file. It also works for stylesheets, grouping them by media type.



use Rack::Bundle, :public_dir => "path to your application's public directory"
run app

Sinatra it's almost the same as above, except you don't need to explicitly call run as Sinatra will handle that:

use Rack::Bundle, :public_dir => Sinatra::Application.public

As for Rails, google around how to add Rack middlewares to the stack. I'm too lazy right now to look it up. But as a general pointer, I know it's in ROOT/config/environment.rb.

A few assumptions

There's a few assumptions that this middleware makes in order to work. Note that all of those will change soon:

  • That your app can write to a directory that's visible to the internet (a.k.a.: the application's public dir). I'm aware that from a security perspective (and for the sake of this working on Heroku), this is a bad idea. Consider this an interim measure so I can get something out quickly.
  • That external Javascripts (read: not hosted on the same web server as the app itself) come first in the DOM. This may or may not be an issue for you, but I've experienced a few. I'll add automatic reordering soon.
  • That you're linking Javascripts inside the tag. It won't break your app if you don't. But scripts that sit outside will be ignored.

How does it work

It parses the response body using Nokogiri, finds every reference to external scripts/stylesheets, locates them in the file system, bundles them, saves the bundle in the application's public directory, and replaces the references in the response for one single reference to the bundle(s).


This project is currently at very early stages of development, which in my case means I haven't bothered making it do what it's supposed to do fast. It's quite possible however that your app will still perform a lot better with it as is, depending on how lazy you were when writing your layouts/templates. After the first release I'll be addressing performance almost exclusively.

Compared to...

rack-bundle is, as of now, a lot simpler (as in less features) than solutions such as Jammit. But it is plug-and-play: you load up the middleware with a few configuration parameters and you're set. No need to modify templates, no helpers, nothing. Oh also, it's framework agnostic, and that's priceless.


Heroku support is in the works. As Heroku doesn't won't allow an application to write to the filesystem, rack-bundle won't work. That will be addressed soon.


It's as free as sneezing. Just give me credit ( if you make some extraordinary out of this.

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