Jekyll Build Tools Part I - Minifying Javascript

I love Jekyll, a static site generator. However it does not automatically minify javascript files.

Rather than use something like gulp.js (which I also dig), I challenged myself to write a script in Ruby. The result was suprisingly concise and I didn't need to add any unnecessary abstraction.

require 'uglifier'

Dir[File.join('_site', '**', '*')].reject { |file| File.directory? file }
.each do |file|
  next unless file[/\.js/]
  compressed = Uglifier.compile(
    File.read(file)
  )
  File.open(file, 'w') { |newfile| newfile.write(compressed) }
  puts "#{file} uglified."
end

I was able to write the code in a functional/streaming style, emulating gulp.js's streaming build principles.

The first line gets all of the files in the directory _site

Dir[File.join('_site', '**', '*')].reject { |p| File.directory? p }

this line does two things

• Using the Dir class, we get an Array of all the items in the _site directory as Files.
• The block passed to the reject method removes the directories from the array.

Now that we have an array of files, we can uglify them by calling the each method on the array and passing a block.

.each do |file|
  next unless file[/\.js/]
  compressed = Uglifier.compile(
    File.read(file)
  )
  File.open(file, 'w') { |newfile| newfile.write(compressed) }
  puts "#{file} uglified."
end

The first line moves to the next item if the file does not have the .js extension. It does this by using the [] regex method on the file object. If there is no match, then the method returns nil, which evaluates to false and moves to the next element in the array.

The next 3 lines call the Uglifier.compile method on a file read as a string.

Then we use Ruby's File class to open the file and write the compressed string.