def runtime
      @runtime ||= ExecJS::ExternalRuntime.new(
        name:        'Node.js (V8)',
        command:     ['nodejs', 'node'],
        runner_path: File.expand_path('../runtime/runner.js', __FILE__)
        )
    end
def runtime
      @runtime ||= ExecJS::ExternalRuntime.new(
        name:        'Node.js (V8)',
        command:     ['nodejs', 'node'],
        runner_path: File.expand_path('../runtime/runner.js', __FILE__)
        )
    end
Internal: Create the ExecJS external runtime with a old runner script that
 maintains the state of 'require', so we can use it to load modules like on
 any Node.JS program.