download.js

var fs = require('fs');
var path = require('path');

require('http').Server(function(req, res) {
  if (!fs.existsSync(req.url)) {
    res.statusCode = 404;
    res.end();
  }
  
  var name = path.basename(req.url);
  res.writeHead(200, {
    'Content-Disposition': 'attachment; filename="' + name + '"'
  });
  
  fs.createReadStream(req.url).pipe(res);
}).listen(8888);