Minify a folder of js with `rake minify`

Rakefile

desc "minify js and put into one file"
task :minify do 
  require 'jsmin'
  
  out = 'min.js'
  glb = '*.js'
  res = ''

  Dir[glb].each do |path|
    res << File.read(path) << "\n"
  end

  res = JSMin.minify(res)
  File.open(out, 'w') {|f| f.write(res) }
end