therubyrhino/README.rdoc

= therubyrhino

* http://github.com/cowboyd/therubyrhino
* irc://irc.freenode.net/therubyrhino

== DESCRIPTION:

Embed the Mozilla Rhino JavaScript interpreter into Ruby

== FEATURES/PROBLEMS:

* Evaluate JavaScript from with in Ruby
* Embed your Ruby objects into the JavaScript world

== SYNOPSIS:

1. JavaScript goes into Ruby
2. Ruby Objects goes into JavaScript
3. Our shark's in the JavaScript!

  require 'rhino'
  
# evaluate some simple javascript
  eval_js "7 * 6" #=> 42

# that's quick and dirty, but if you want more control over your
# environment, use a Context:
  Rhino::Context.open do |cxt|
    cxt['foo'] = "bar"
    cxt.eval('foo') # => "bar"
  end

# evaluate a ruby function from JS
  
  Rhino::Context.open do |context|
    context["say"] = lambda {|word, times| word * times}
    context.eval("say("Hello", 3)") #=> HelloHelloHello
  end
  
# embed a ruby object into your JS environment

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

  Rhino::Context.open do |context|
    context["math"] = MyMath.new
    context.eval("math.plus(20, 22)") #=> 42
  end
  
# make a ruby object *be* your JS environment
  math = MyMath.new
  Rhino::Context.open(:with => math) do |context|
    context.eval("plus(20, 22)") #=> 42
  end
  
  #or the equivalent
  
  math.eval_js("plus(20, 22)")

# Configure your embedding setup

  # Make your standard objects (Object, String, etc...) immutable
  Rhino::Context.open(:sealed => true) do |context|
    context.eval("Object.prototype.toString = function() {}") # this is an error!
  end
  
  #Turn on Java integration from javascript (probably a bad idea)
  Rhino::Context.open(:java => true) do |context|
    context.eval("java.lang.System.exit()") # it's dangerous!
  end

  #limit the number of instructions that can be executed in order to prevent
  #rogue scripts
  Rhino::Context.open(:restrictable => true) do |context|
    context.instruction_limit = 100000
    context.eval("while (true);") # => Rhino::RunawayScriptError
  end

  #limit the time a script executes
  #rogue scripts
  Rhino::Context.open(:restrictable => true, :java => true) do |context|
    context.timeout_limit = 1.5 # seconds
    context.eval %Q{ 
        for (var i = 0; i < 100; i++) {
            java.lang.Thread.sleep(100);
        }
    } # => Rhino::ScriptTimeoutError
  end

==== 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|
    eval_js file, "mysource.js"
  end

# or load it by filename
  Rhino::Context.open do |context|
    context.load("mysource.js")
  end

==== Configurable Ruby access

By default accessing Ruby objects from JavaScript is compatible with *therubyracer*:
https://github.com/cowboyd/therubyracer/wiki/Accessing-Ruby-Objects-From-JavaScript

Thus you end-up calling arbitrary no-arg methods as if they were JavaScript properties, 
since instance accessors (properties) and methods (functions) are indistinguishable:

  Rhino::Context.open do |context|
    context['Time'] = Time
    context.eval('Time.now')
  end

However, you can customize this behavior and there's another access implementation
that attempts to mirror only attributes as properties as close as possible:

  class Foo
    attr_accessor :bar
    
    def initialize
      @bar = "bar"
    end
    
    def check_bar
      bar == "bar"
    end
  end
  
  Rhino::Ruby::Scriptable.access = :attribute
  Rhino::Context.open do |context|
    context['Foo'] = Foo
    context.eval('var foo = new Foo()')
    context.eval('foo.bar') # get property using reader
    context.eval('foo.bar = null') # set property using writer
    context.eval('foo.check_bar()') # called like a function
  end

If you happen to come up with your own access strategy, just set it directly :

  Rhino::Ruby::Scriptable.access = FooApp::BarAccess.instance

=== Safe by default

The Ruby Rhino 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 objects and 
functions. Nothing from the Ruby world is accessible at all.

For Ruby objects that you explicitly embed into JavaScript, only the +public+ 
methods "defined in their classes" are exposed by default e.g.

  class A
    def a
      "a"
    end
  end

  class B < A
    def b
      "b"
    end
  end


  Rhino::Context.open do |cxt|
    cxt['a'] = A.new
    cxt['b'] = B.new
    cxt.eval("a.a()") # => 'a'
    cxt.eval("b.b()") # => 'b'
    cxt.eval("b.a()") # => 'TypeError: undefined property 'a' is not a function'
  end
  
==== Using a custom Rhino version

Officially supported versions of Rhino's _js.jar_ are packaged separately as 
*therubyrhino_jar* gem. Make sure you're using the latest gem version if you 
feel like missing something available with Rhino. For experimenters the jar can
be overriden by defining a +Rhino::JAR_PATH+ before +require 'rhino'+ e.g. :

  module Rhino
    JAR_PATH = File.expand_path('lib/rhino/build/rhino1_7R5pre/js.jar')
  end
  # ...
  require 'rhino'

==== Context customizations

Just like the JVM packaged Rhino scripting engine, therubyrhino gem supports
specifying JavaScript context properies (optimization level and language version)
using system properties e.g. to force interpreted mode :

  jruby -J-Drhino.opt.level=-1 -rtherubyrhino -S ...

You might also set these programatically as a default for all created contexts :

  Rhino::Context.default_optimization_level = 1
  Rhino::Context.default_javascript_version = 1.6

Or using plain old JAVA_OPTS e.g. when setting JavaScript version :

  -Drhino.js.version=1.7

== Rhino

Rhino is currently maintained at https://github.com/mozilla/rhino
Release downloads are available at http://www.mozilla.org/rhino/download.html
Rhino is licensed under the MPL 1.1/GPL 2.0 license.

== REQUIREMENTS:

* JRuby >= 1.6

== INSTALL:

* jruby -S gem install therubyrhino

== LICENSE:

(The MIT License)

Copyright (c) 2009-2012 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.