var ua = request.headers['user-agent'],
    $ = {};

if (/mobile/i.test(ua))
    $.Mobile = true;

if (/like Mac OS X/.test(ua)) {
    $.iOS = /CPU( iPhone)? OS ([0-9\._]+) like Mac OS X/.exec(ua)[2].replace(/_/g, '.');
    $.iPhone = /iPhone/.test(ua);
    $.iPad = /iPad/.test(ua);
}

if (/Android/.test(ua))
    $.Android = /Android ([0-9\.]+)[\);]/.exec(ua)[1];

if (/webOS\//.test(ua))
    $.webOS = /webOS\/([0-9\.]+)[\);]/.exec(ua)[1];

if (/(Intel|PPC) Mac OS X/.test(ua))
    $.Mac = /(Intel|PPC) Mac OS X ?([0-9\._]*)[\)\;]/.exec(ua)[2].replace(/_/g, '.') || true;

if (/Windows NT/.test(ua))
    $.Windows = /Windows NT ([0-9\._]+)[\);]/.exec(ua)[1];

http://stackoverflow.com/questions/6163350/server-side-browser-detection-node-js

Browser detection before sending any resources to the client.

NodeJS: Server-side browser detection

javascript

JavaScript