Regarding Martech script loading early on pageload, affecting the performance of the page.

[suhjainadobe]

Hello,
Currently, martech script is relying on MILO_EVENTS.DEFERRED event to check if the page has loaded or they wait for 3 seconds to run their scripts. But if there are fragments on the page, they use the loadArea function as well which has loadDeferred function triggering MILO_EVENTS.DEFERRED event before the whole page loads. Thus, the martech scripts starts loading early causing the TBT to increase as it blocks the main script.

Therefore, I would like to have your viewpoint on if it's ok to call the loadDeferred inside the isDoc check which checks if the function is being called by the fragment or the document. By doing this, we have observed that the martech scripts are loading after the page loading has completed, decreasing the TBT.
Before : https://pagespeed.web.dev/analysis/https-main--cc--adobecom-hlx-live-creativecloud-business-teams-resources-how-to-marketing-plan/yx67vje1ko?form_factor=mobile
After: https://pagespeed.web.dev/analysis/https-main--cc--adobecom-hlx-live-creativecloud-business-teams-resources-how-to-marketing-plan/jxe7tsuyvx?form_factor=mobile

For same, we will have to test other blocks like carousel, tables, tabs etc which listen to MILO_EVENTS.DEFERRED event for their respective operations.

[chrischrischris]

If the MILO_EVENTS.DEFERRED event only fires for the document, then any blocks which listen for it that are in fragments will not work properly, so another solution will need to be found.

I don't see where martech loading depends on the deferred event though ... when target or MEP is not enabled, then loadMartech happens in the loadPostLcp function. loadPostLcp only fires for the document and not for fragments.

[suhjainadobe]

The martech team has written the following code in their script to listen to the milo:deferred event for initialise the martech scripts.
`var
w = window,
d = document,
wm = w.marketingtech,
_satellite = w._satellite,
marketingGlobal = true,
marketingCS = true;

Promise.resolve()
// 1) milo:deferred depending on the situation
.then(function () {
return new Promise(function (resolve) {
// if we are on a milo page, wait for milo:deferred
if (wm && wm.milo) {
// TODO: What if milo:deferred already fired? Will we miss it?
// TODO: We need a flag to tell us whether milo:deferred already fired
d.addEventListener('milo:deferred', resolve);
// otherwise just resolve
} else {
resolve();
}
});
})
// 2) also just make sure that window loaded has fired as well
.then(function () {
return new Promise(function (resolve) {
if (d.readyState === 'complete') {
resolve();
} else {
w.addEventListener('load', resolve);
}
});
})
// 3) wait another 4 seconds
.then(function () {
return new Promise(function (resolve) {
setTimeout(resolve, 4000);
});
})
// 4) make sure that we have been given consent
.then(function () {
// if it's a student, exit immediately, we don't fire any of these tags
// for students...
if (_satellite.getVar('isStudent')) {
return;
}

var consent = _satellite.getVar('consent');

//check for marketingTag Flags
if (wm && (wmm = wm.marketingTags)) {
  if (wmm.disableGlobalTags) {
    marketingGlobal = false;
  }
  if (wmm.disableContentsquare) {
    marketingCS = false;
  }
}

consent('C0002', function () {
  if (marketingCS) {
    _satellite.track('CSC2');
  }
  if (marketingGlobal) {
    _satellite.track('C2');
  }
});

if (marketingGlobal) {
  consent('C0004', function () {
    _satellite.track('C4');
  });
}

});
`

[suhjainadobe]

In this case can we introduce a new event for martech team which will tell the martech team that the page has been loaded and they can initialise the scripts.

[salonijain3]

@suhjainadobe
There was a discussion on this in the MEP meeting, and @chrischrischris showed us that Milo deferred for fragments does not bubble up and only the milo deferred for document is getting fired for launch, lets look into this a bit more to confirm and go from there.

cc: @mokimo @aishwaryamathuria