Nodejs error encoding when get external site's content

I used get method of request module to get content of external site. If encoding of external site is utf-8, it is ok, but it has display error with other encodings such as shift-jis

function getExternalUrl(request, response, url){

    mod_request.get(url, function (err, res, body) {
    //mod_request.get({uri: url, encoding: 'binary'}, function (err, res, body) {
        if (err){
            console.log("\terr=" + err);
        }else{
            var result = res.body;
            // Process res.body
            response.write(result);
        }
        response.end();
    });
}

How can I get content of external site with correct encoding?

via GSP