class Origami::PDF::JavaScript::Global

def [](name)
    @vars[name][:value] if @vars.include?(name)
end

def []=(name, value)
    @vars[name] ||= {callbacks: []}
    @vars[name][:value] = value
    @vars[name][:callbacks].each do |callback|
        callback.call(value)
    end
end

def initialize(engine)
    super(engine)
    @vars = {}
end