How to get network data with JavaScript

How to get network data with JavaScript

Selenide Advent Calendar
Day 17

Good night!

In the yesterday post we tried to get browser logs with “goog:loggingPrefs” capability.
Now we will try to get browser network data with JavaScript.

It’s simple. We just need to call this JavaScript in the end of test:

String js = 
   "var performance = window.performance || window.mozPerformance" +
                   " || window.msPerformance || window.webkitPerformance || {};" +
   " return performance.getEntries() || {};";
String netData = executeJavaScript(js).toString();"Network traffic: {}", netData);

The result looks like this:

Network traffic: [
  {name=, connectEnd=0, connectStart=0, decodedBodySize=32582, domComplete=724, domContentLoadedEventEnd=119, domContentLoadedEventStart=115, domInteractive=104, domainLookupEnd=0, domainLookupStart=0, duration=724, encodedBodySize=32582, entryType=navigation, fetchStart=0, initiatorType=navigation, loadEventEnd=724, loadEventStart=724, nextHopProtocol=http/1.1, redirectCount=0, redirectEnd=0, redirectStart=0, requestStart=0, responseEnd=0, responseStart=0, secureConnectionStart=0, serverTiming=[], startTime=0, transferSize=0, type=navigate, unloadEventEnd=10, unloadEventStart=9, workerStart=0},
  {name=, connectEnd=12, connectStart=12, decodedBodySize=8177, domainLookupEnd=12, domainLookupStart=12, duration=29, encodedBodySize=8177, entryType=resource, fetchStart=12, initiatorType=link, nextHopProtocol=http/1.1, redirectEnd=0, redirectStart=0, requestStart=12, responseEnd=41, responseStart=21, secureConnectionStart=0, serverTiming=[], startTime=12, transferSize=0, workerStart=0},
  {name=, connectEnd=13, connectStart=13, decodedBodySize=84245, domainLookupEnd=13, domainLookupStart=13, duration=28, encodedBodySize=84245, entryType=resource, fetchStart=13, initiatorType=script, nextHopProtocol=http/1.1, redirectEnd=0, redirectStart=0, requestStart=13, responseEnd=41, responseStart=21, secureConnectionStart=0, serverTiming=[], startTime=13, transferSize=0, workerStart=0}


  • You don’t need to setup the browser. It works out of the box.
  • It works in all browsers (I guess?)


  • We still don’t see request body here.
  • It’s not a valid JSON. We cannot parse it with a standard parser. Would need to create some custom parser.

But this option is quite ok to look at and understand what happens.

What’s next?

Our last hope to get request bodies is built-in proxy server. We will look at it next time.

Andrei Solntsev