Opal is a Ruby to JavaScript source-to-source compiler.
It also has an implementation of the Ruby corelib and stdlib.
Community:
Code:
Sponsors:
See the website for more detailed instructions and guides for Rails, jQuery, Sinatra, rack, CDN, etc. https://opalrb.com.
Contents of app.rb:
puts 'Hello world!'
Then from the terminal
$ opal --compile app.rb > app.js # The Opal runtime is included by default
# but can be skipped with the --no-opal flag
The resulting JavaScript file can be used normally from an HTML page:
<script src="app.js"></script>
Be sure to set the page encoding to UTF-8 inside your <head> tag as follows:
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<script src="app.js"></script>
…
</head>
<body>
…
</body>
</html>
Just open this page in a browser and check the JavaScript console.
Opal.compile is a simple interface to just compile a string of Ruby into a
string of JavaScript code.
Opal.compile("puts 'wow'") # => "(function() { ... self.$puts("wow"); ... })()"
Running this by itself is not enough; you need the opal runtime/corelib.
Opal::Builder can be used to build the runtime/corelib into a string.
Opal::Builder.build('opal') #=> "(function() { ... })()"
or to build an entire app including dependencies declared with require:
builder = Opal::Builder.new
builder.build_str('require "opal"; puts "wow"', '(inline)')
File.binwrite 'app.js', builder.to_s # must use binary mode for writing
opal-parser allows you to eval Ruby code directly from your HTML (and from Opal) files without needing any other building process.
So you can create a file like the one below, and start writing ruby for your web applications.
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<script src="https://cdn.opalrb.com/opal/current/opal.js"></script>
<script src="https://cdn.opalrb.com/opal/current/opal-parser.js" onload="Opal.load('opal-parser')"></script>
<script type="text/ruby">
puts "hi"
</script>
</head>
<body>
</body>
</html>
Just open this page and check the JavaScript console.
NOTE: Although this is possible, this is not really recommended for production and should only be used as a quick way to get your hands on opal.
Setup the project:
$ bin/setup
The test suite can be run using:
$ bundle exec rake
This command will run all RSpec and MSpec examples in sequence.
MSpec tests can be run with:
$ rake mspec
Alternatively, you can just load up a rack instance using rackup, and
visit http://localhost:9292/ in any web browser.
RSpec tests can be run with:
$ rake rspec
A Guardfile with decent mappings between specs and lib/corelib/stdlib files is in place.
Run bundle exec guard -i to start guard.
What code is supposed to run where?
lib/ code runs inside your Ruby env. It compiles Ruby to JavaScript.opal/ is the runtime+corelib for our implementation (runs in browser).stdlib/ is our implementation of Ruby's stdlib. It is optional (runs in browser).The lib directory holds the Opal parser/compiler used to compile Ruby
into JavaScript. It is also built ready for the browser into opal-parser.js
to allow compilation in any JavaScript environment.
This directory holds the Opal runtime and corelib implemented in Ruby and JavaScript.
Holds the stdlib currently supported by Opal. This includes Observable,
StringScanner, Date, etc.
Any problems encountered using the browsers listed above should be reported as bugs.
(Current - 1) or Current denotes that we support the current stable version of the browser and the version that preceded it. For example, if the current version of a browser is 24.x, we support the 24.x and 23.x versions.
12.1x or (Current - 1) or Current denotes that we support Opera 12.1x as well as the last 2 versions of Opera. For example, if the current Opera version is 20.x, then we support Opera 12.1x, 19.x and 20.x but not Opera 15.x through 18.x.
This project exists thanks to all the people who contribute. 
Opal will broadly follow semver as a version policy, trying to bump the major version when introducing breaking changes. Being a language implementation we're also aware that there's a fine line between what can be considered breaking and what is expected to be "safe" or just "additive". Moving forward we'll attempt to better clarify what interfaces are meant to be public and what should be considered private.
Thank you to all our backers! 🙏 [Become a backer]
Support this project by becoming a sponsor. Your logo will show up here with a link to your website. [Become a sponsor]
(The MIT License)
Copyright (C) 2013-2021 by Adam Beynon and the Opal contributors
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
FAQs
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We found that opal demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 3 open source maintainers collaborating on the project.
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