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dia nashorner

Embed the Mozilla Rhino Nashorn JavaScript interpreter into Ruby.

Nashorn JavaScript engine is part of OpenJDK (since 8u40), try jjs -v.

Requirements

Java (Open/Oracle JRE) >= 8

jruby -S gem install dienashorner # make sure you have JRuby >= 1.7.x

Features

  • Evaluate JavaScript bits from the Ruby side
  • Embed Ruby objects into the JavaScript world
require 'nashorn'
  • evaluate some simple JavaScript
Nashorn.eval 'true + 100' #=> 101
Nashorn.eval_js '"4" + 2' #=> "42"
include Nashorn
eval_js "'1' + '' * 2" #=> "10"
  • if you need more control, use a Context
Nashorn::Context.open do |js|
  js['foo'] = "bar"
  js.eval('foo') # => "bar"
end
  • evaluate a Ruby function from JavaScript
Nashorn::Context.open do |js|
  js['say'] = lambda { |word, times| word * times }
  js.eval("say('Szia', 3) + '!'") #=> SziaSziaSzia!
end
  • embed a Ruby object into your JavaScript environment
class MyMath
  def plus(a, b); a + b + 1 end
end

Nashorn::Context.open do |js|
  js["math"] = MyMath.new
  js.eval("math.plus(20, 21)") #=> 42
end
  • make a Ruby object a JavaScript (global) environment
math = MyMath.new
Nashorn::Context.open(:with => math) do |js|
  js.eval("plus(20, 21)") #=> 42
end

Context Options

Mostly the same as with jjs e.g. Nashorn::Context.open(:strict => true).

Loading .js

  File.open('___.js') { |file| eval_js file }
  Nashorn::Context.open { |js| js.load('___.js') }

Configurable Ruby access

Ported over from Rhino

Rhino Compatibility

Nashorn was inspired (and crafted) from Rhino a.k.a therubyrhino JRuby gem. Far from being a drop-in replacement although there's require 'nashorn/rhino'.

ExecJS

dienashorner gem ships with an ExecJS compatible runtime, its best to load it (require 'nashorn/execjs/load') before ExecJS's auto-detection takes place :

gem 'execjs', require: false
gem 'dienashorner', platform: :jruby, require: [ 'nashorn/execjs/load', 'execjs' ]

when auto-detection is not used, set the runtime manually :

require 'execjs/module'
require 'nashorn/execjs/load'
ExecJS.runtime = ExecJS::NashornRuntime.new

Less.rb

Less.rb seems to be working (with hacks), for now you will need to :require 'nashorn/rhino/less' before require 'less'.

Copyright

Copyright (c) 2017 Karol Bucek. Apache License v2 (see LICENSE for details).