Getting Started Join the conversation
Opal is a Ruby to JavaScript source-to-source compiler.
It comes packed with the Ruby corelib you know and love.
It is both fast as a runtime and small in its footprint.
Opal is truly amazing and it has taken me in a whole new direction.โ @mistergibson from Gitter, on Jan 22 2018
[about Opal 1.7] Fantastic! No failing specs for [isomorfeus](https://github.com/isomorfeus/isomorfeus-project#readme), asset size reduced, performance a tiny bit improved too :+1:โ @janbiedermann, on Dec 25th 2022
These guys are great. We have a large production app (www.catprint.com) that thanks to opal is 100% RUBY. The UI part is about 17K of opal code, using the hyperstack (www.hyperstack.org) framework.โ @catmando from Gitter, on Dec 1 2018
In practice Opal == MRI Ruby, very reliable and solid.
class User
attr_accessor :name
def initialize(name)
@name = name
end
def admin?
@name == 'Admin'
end
end
user = User.new('Bob')
# the output will go to your browser's console
puts user
puts user.admin?
Add opal
, rack
and rackup
to your Gemfile
.
bundle add opal rack rackup
Setup the Opal rack-app in your config.ru
as follows:
require 'opal'
run(Opal::SimpleServer.new do |s|
# the name of the ruby file to load. To use more files they must be required from here (see app)
s.main = 'application'
# the directory where the code is (add to opal load path )
s.append_path 'app'
end)
Add a file named application.js.rb
to app/
with your hello world:
require 'opal'
require 'native'
$$.alert 'Hello World from Opal!'
Then start the server with bundle exec rackup
and visit http://localhost:9292.
Learn more about Opal Sprockets
Add opal-rails
to your Rails app's Gemfile
:
bundle add opal-rails
Rename app/assets/javascripts/application.js
to app/assets/javascripts/application.js.rb
and replace its contents with this code:
require 'opal'
require 'opal_ujs'
require 'turbolinks'
require_tree '.'
Create a "Hello World" controller:
bin/rails generate controller HelloWorld index
Replace the contents of app/assets/javascripts/hello_world.js.rb
with:
Document.ready? do
Element.find('body').html = '<h1>Hello World from Opal!</h1>'
end
Start the server with bin/rails server
and visit: http://localhost:3000/hello_world/index.
Install opal
from Rubygems:
gem install opal
Write this code to hello_world.js.rb
:
require 'ostruct'
greeting = OpenStruct.new(type: :Hello, target: :World, source: :Opal)
puts "#{greeting.type} #{greeting.target} from #{greeting.source}!"
Run it with Node.js (assuming it's installed):
opal hello_world.js.rb
# => Hello World from Opal!
Compile it to a JavaScript file:
opal -c hello_world.js.rb > hello_world.js
node hello_world.js
# => Hello World from Opal!
For a full list of supported options see:
opal --help
Opal is hosted on GitHub .
You can join the community by chatting on Slack.
Ask questions on stackoverflow by using the #opalrb tag.
Discuss on the mailing list or on Twitter @opalrb.