Is the code to get _domContentLoadedTime correct?

[Kota]

Your question

I am trying to get performance metrics for a site I accessed using the browsertime command.

browsertime https://www.youtube.com/ -n 1 --headless true --b chrome

For example, part of the HAR file obtained by executing the above command looks like this:

"pageTimings": {
    "onContentLoad": 3344.498,
    "onLoad": 4376.424,
    "_firstPaint": 2887,
    "_largestContentfulPaint": 3992,
    "_firstContentfulPaint": 2887,
    "_domInteractiveTime": 3345,
    "_domContentLoadedTime": 3345
},

I have a question about how to get the _domContentLoadedTime shown here. Looking at this code, I see that you are using domContentLoadedEventStart to get _domContentLoadedTime, is this correct?

According to MDN

The DOMContentLoaded event fires when the HTML document has been completely parsed, and all deferred scripts (<script defer src="…"> and <script type="module">) have downloaded and executed. It doesn't wait for other things like images, subframes, and async scripts to finish loading.

So, I think _domContentLoadedTime should be obtained as follows:

// domContentLoadedTime: Number(t.domContentLoadedEventStart.toFixed(d)),
domContentLoadedTime: Number(t.domContentLoadedEventEnd.toFixed(d)),

Thank you for your feedback.

[Peter Hedenskog]

Hi @yagikota thanks for creating the issue! Yes I thinks it's unclear. I think the metrics in https://github.com/sitespeedio/browsertime/blob/main/browserscripts/timings/pageTimings.js comes from a old Google Analytics guidance, so domContentLoadedTime isn't the exact same thing as the DOMContentLoaded event. The start fires right before the event https://w3c.github.io/navigation-timing/#dom-performancetiming-domcontentloadedeventstart and the end fires right after. I personally uses https://github.com/sitespeedio/browsertime/blob/main/browserscripts/timings/navigationTiming.js when monitoring a site. Maybe the best would be just to remove the pageTimings to avoid confusion.

[Kota]

thanks!