Extract largest image thumbnail from url using node and cheerio

gistfile1.txt

var   cheerio = require('cheerio')
    , Shred = require('shred')
    , shred = new Shred()
    , http = require('http')
    , URL = require('url');

var server = http.createServer(function(request, response) {
  var url, urlToDiscover;
  url = URL.parse(request.url, true);
  urlToDiscover = url.query['url'];
  return startDiscovery(urlToDiscover, function(theImageURL) {
    if (theImageURL != null) {
      response.writeHead(200, {
        "Content-Type": 'application/json'
      });
      return response.end(JSON.stringify(theImageURL));
    } else {
      console.log("Did not find image for " + urlToDiscover);
      response.writeHead(404, "Cant find theImage");
      return response.end();
    }
  });
});

server.listen(process.env.PORT || 5000, '0.0.0.0');

var startDiscovery = function(url, cb) {
  return shred.get({
    url: url,
    on: {
      redirect: function(response) {
        return discoverImage(response.request.url, null, cb);
      },
      200: function(response) {
        return discoverImage(response.request.url, response.content.data, cb);
      }
    }
  });
};

var discoverImage = function(url, data, cb) {
  var discoveredURL;
  discoveredURL = discoverImageFromURL(url);
  if (data) {
    discoveredURL || (discoveredURL = discoverImageFromData(url, data));
  }
  discoveredURL = cleanURL(url, discoveredURL);
  return cb(discoveredURL);
};

var cleanURL = function(baseURL, discoveredURL) {
  if (!discoveredURL) {
    return null;
  }
  if (discoveredURL.indexOf("/") === 0) {
    return "" + baseURL + discoveredURL;
  }
  return discoveredURL;
};

var discoverImageFromURL = function(url) {
  console.log(url.indexOf('yfrog'));
  if (url.indexOf('yfrog') !== -1) {
    return url + ":medium";
  }
};

var discoverImageFromData = function(url, data) {
  var $, currDimension, image, images, maxDimension, maxImage, _i, _len;
  $ = cheerio.load(data);
  images = $('img');
  maxImage = null;
  maxDimension = 0;
  for (_i = 0, _len = images.length; _i < _len; _i++) {
    image = images[_i];
    currDimension = $(image).attr('width') * $(image).attr('height');
    if (currDimension > maxDimension) {
      maxDimension = currDimension;
      maxImage = image;
    }
  }
  return $(maxImage).attr('src');
};