Count the number of domains used to load a page (see http://www.peterbe.com/plog/number-of-domains)

count-page-domains.js

/* global phantom */
// Inspired by https://gist.github.com/cjoudrey/1341747
"use strict";

var system = require('system'),
    webPage = require('webpage');

if (system.args.length != 2) {
    console.log('Usage:', system.args[0], 'URL');
    phantom.exit(2);
}

var url = system.args[1],
    original_domain = getDomain(url);

var page = webPage.create();

var maxRenderWait = 30 * 1000,
    minQuietTime = 1000, // Minimum time (ms) before assuming load has completed
    pendingRequestCount = 0,
    lastRequestTime;

var domains = {};

page.viewportSize = { width: 1280, height : 1024 };

page.settings.resourceTimeout = 5000;

page.onConsoleMessage = function(msg, lineNum, sourceId) {
    if (lineNum || sourceId) {
        console.log('PAGE CONSOLE:', msg, '(Source:', lineNum, sourceId, ')');
    } else {
        console.log('PAGE CONSOLE:', msg);
    }
};

function getDomain(url) {
  return url.split('//')[1].split('/')[0];
}

page.onResourceTimeout = function(e) {
  console.error('HTTP', e.errorCode, e.errorString, 'loading', e.url);
  phantom.exit(1);
};

page.onResourceRequested = function (req) {
    pendingRequestCount++;
    lastRequestTime = Date.now();

    if (req.url.substring(0, 5) != 'data:') {
        domains[getDomain(req.url)] = 1;
    }

    console.debug('Request start', req.id, req.url.substring(0, 70));
};

page.onResourceReceived = function (res) {
    if (!res.stage || res.stage === 'end') {
        pendingRequestCount--;
        console.debug('Request end', res.id, res.status, res.url);
    }
};

function checkLoadComplete() {
    var elapsed = Date.now() - startTime;

    console.debug(pendingRequestCount, 'requests pending;', elapsed, 'ms');

    if (pendingRequestCount > 0 && (elapsed < maxRenderWait)) {
        return;
    }

    if (minQuietTime > (Date.now() - lastRequestTime)) {
        console.log('Waiting at least', minQuietTime, 'ms for deferred load events to complete');
        return;
    }

    if (elapsed > maxRenderWait) {
        console.warn('Render terminated after', elapsed, 'milliseconds; ',
                     pendingRequestCount, 'requests still pending');
    }

    var domainCount = 0;
    for (var domain in domains) {
        console.log('DOMAIN:', domain);
        domainCount++;
    }

    console.log('DOMAIN COUNT:', domainCount);

    phantom.exit();
}


var startTime = Date.now();

lastRequestTime = startTime;

console.log('Opening', url);

page.open(url, function (status) {
    console.log('onLoadFinished event triggered after', Date.now() - startTime, 'milliseconds');

    if (status !== 'success') {
        console.error('Error', status, 'loading', url);
        phantom.exit(1);
    } else {
        // Attempt to trigger deferred loaders by scroll to the bottom of the page
        page.evaluate(function() {
            var __testTriggerScroll = function () {
                window.document.body.scrollTop = 0;
                window.document.body.scrollTop = document.body.scrollHeight;
                console.log("Scrolled window");
            };

            window.addEventListener("load", function load() {
                window.setTimeout(__testTriggerScroll, 100);
                console.log('window load event fired, triggering scroll event');
            });

            window.setTimeout(__testTriggerScroll, 50);
        });
    }
});

// We'll check under the minQuietTime threshold to avoid aliasing:
setInterval(checkLoadComplete, Math.floor(minQuietTime / 3));