gistfile1.rb

require 'rubygems'
require 'net/http'
require 'uri'
require 'json'

class GoogleClosure
  class Error < RuntimeError; end
  
  HOST = URI.parse('http://closure-compiler.appspot.com/compile')

  def self.compile(contents)
    response = Net::HTTP.post_form(HOST, {
      :js_code => contents,
      :compilation_level => 'SIMPLE_OPTIMIZATIONS',
      :output_format => 'json',
      :output_info => 'compiled_code',
    })
    
    case response
    when Net::HTTPSuccess
      info = JSON.parse(response.body)
      
      if info["serverErrors"]
        raise Error, "Errors returned from closure-compiler service: #{info["serverErrors"].inspect}"
      else
        return info["compiledCode"]
      end
    else
      raise Error, "Unexpected response from closure-compiler service: #{response.class}"
    end
  end
end

p GoogleClosure.compile("var f = function() { var foo = 76; return foo;}")