Pass additional arguments to node.js callack

I have created a rest client to make calls outside of my application. I want to send the data I receive back from the rest calls to the client's web browser.

Something like the following, but what is the best way to structure the code to allow access to the response to write back to the web browser with as loose coupling as possible? I don't want to define the rest client within a request handler.

var servReq = http.request(options, function(restResponse){
    var status = restResponse.statusCode
    var headers = restResponse.headers
    restResponse.setEncoding("utf8");
    d='';
    restResponse.on('data', function(chunk){
        d += chunk;
    })
    restResponse.on('end', function(restResponse){
        // res would be a response to write back to the client's web browser
        // with the data received from the rest client.
        res.writeHead(200, {"content-type":"text/plain"})    
        res.write(d)
        res.end();
    })
}