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Embed the V8 Javascript Interpreter into Ruby

README.md

therubyracer

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DESCRIPTION

Embed the V8 JavaScript interpreter into Ruby.

FEATURES

  • Evaluate JavaScript from within Ruby
  • Embed your Ruby objects into the JavaScript world
  • Manipulate JavaScript objects and call JavaScript functions from Ruby
  • API compatible with the The Ruby Rhino (for JRuby: http://github.com/cowboyd/therubyrhino)

SYNOPSIS

gem install therubyracer

then in your Ruby code

require 'v8'
# or if using bundler (as with Rails), add the following to your Gemfile
gem "therubyracer"

evaluate some simple JavaScript

cxt = V8::Context.new
cxt.eval('7 * 6') #=> 42

access values inside your JavaScript context from Ruby

cxt.eval 'var val = {num: 5, fun: function isTruthy(arg) { return !!arg }}'
val = cxt[:val] #=> V8::Object
cxt[:val] == cxt.scope.val #=> true
val.num #=> 5
val.isTruthy(1) #=> true

this includes references to JavaScript functions

truthy = val[:isTruthy] #=> V8::Function
truthy.call(' ') #=> true
truthy.call(0) #=> false

embed values into the scope of your context

cxt['foo'] = "bar"
cxt.eval('foo') # => "bar"

embed Ruby code into your scope and call it from JavaScript

cxt["say"] = lambda {|this, word, times| word * times}
cxt.eval("say('Hello', 3)") #=> HelloHelloHello

embed a Ruby object into your scope and access its properties/methods from JavaScript

class MyMath
  def plus(lhs, rhs)
    lhs + rhs
  end
end

cxt['math'] = MyMath.new
cxt.eval("math.plus(20,22)") #=> 42

make a Ruby object be your global JavaScript scope.

math = MyMath.new
V8::Context.new(:with => math) do |cxt|
  cxt.eval("plus(20,22)") #=> 42
end

you can do the same thing with Object#eval_js

math.eval_js("plus(20,22)")

Different ways of loading JavaScript source

In addition to just evaluating strings, you can also use streams, such as files.

evaluate bytes read from any File/IO object:

File.open("mysource.js") do |file|
  cxt.eval(file, "mysource.js")
end

or load it by filename

cxt.load("mysource.js")

Safe by default, dangerous by demand

The Ruby Racer is designed to let you evaluate JavaScript as safely as possible unless you tell it to do something more dangerous. The default context is a hermetically sealed JavaScript environment with only the standard JavaScript objects and functions. Nothing from the Ruby world is accessible at all.

For Ruby objects that you explicitly embed into JavaScript, by default only the public methods below Object are exposed by default. E.g.

class A
  def a
    "a"
  end

  def to_s
    super
  end
end

class B < A
  def b
    "b"
  end
end


V8::Context.new do |cxt|
  cxt['a'] = A.new
  cxt['b'] = B.new
  cxt.eval("a.a") # => 'a'
  cxt.eval("b.b") # => 'b'
  cxt.eval("b.a") # => 'a'
  cxt.eval("b.to_s") # => #<B:0x101776be8> (because A explicitly defined it)
  cxt.eval("b.object_id") #=> undefined, object_id is on Object
end

If needed, you can override the Ruby Access to allow whatever behavior you'd like.

More documentation can be found on the GitHub wiki

Protecting Your CPU cycles

When running untrusted JavaScript code, you not only have to protect which functions it has access to, but also how much of your CPU it can consume. Take this simple, yet thoroughly malicious script:

while (true) {}

It will loop forever and never return control to the calling Ruby thread. To protect against such JavaScript code that either deliberately or accidentally runs longer that it should, you can set an explicit timeout on your context. If the code runs longer that the allowed timeout, then it will throw an exception. Note that this exception could be raised at any point in the execution of the JavaScript.

To specify the timeout (in milliseconds), pass in the timeout option to the constructor.

cxt = V8::Context.new timeout: 700
cxt.eval "while (true);" #= exception after 700ms!

PREREQUISITES

The Ruby Racer requires the V8 Javascript engine, but it offloads the handling of this dependency to the libv8 gem. Because libv8 is now a gem dependency, you do not need a separate libv8 entry in your project's Gemfile.

Please see libv8 for V8 runtime installation options.

DEVELOP

git clone git://github.com/cowboyd/therubyracer.git
cd therubyracer
bundle install
rake compile

Sponsored by

The Frontside

LICENSE:

(The MIT License)

Copyright (c) 2009,2010,2011,2012 Charles Lowell

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.

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