Will dataLayer.push() definitely send data to google when triggered on an anchor?

Question

This may seem like a simple question, but it doesn't seem to be answered anywhere that i can find.

I am writing an onClick event handler that simply calls dataLayer.push() when an anchor is clicked.

Is dataLayer.push() a synchronous operation?

Will the GET request to google definitely be sent, even though the browser has unloaded the page it was requested from due to the link being followed?

Some browsers show the connection get cancelled, some show it success.

My question is if the computer is slow, is it possible for the page to get unloaded before the request is sent?

This is why i assume that google started using the eventCallback property to redirect the user after the link has been followed. e.g. https://developers.google.com/tag-manager/enhanced-ecommerce#product-clicks

This source code does not include the click handler, but implies that the onClick event should stop propogation and let the eventCallback function set document.location.

However, as soon as you cancel the event, all its information has gone.

This (in my opinion) is just the wrong way to do it. e.g. (CTRL or COMMAND) + Click opens a new tab on browsers. This will not work unless the onClick event handler allows the prorogation to continue.

Relying on eventCallback also means that if the google scrips didn't load for one of the many reasons it could (but is still unlikely), your links don't work. And your site is broken.

So this leaves the correct way to do it for the onClick event handler to allow the event to propagate and return true.

Which also means that dataLayer.push() would need return after the GET request was sent for any of this to work properly.

Code example: NOTE: You will get mixed results in mixed environments.

<a href="/somewhere-else">Link</a>


$(document).on('click', 'a', function(event) {

    // Is dataLayer.push() guaranteed to fire a GET ?
    // data set externally
    dataLayer.push(data);

    return true;

});

Is there anyone out there that can guarantee that the GET request will get fired to the google server?

Have the google developers forgotten something here?

EDIT: Updated title to be more relevant to the question.

Answer 1

datalayer.push does not send anything to Google. It pushes objects with key/value pairs to the datalayer array. This might contain an event which in turn fires a tag. Whether the tag is sent depends on the setup of the tag, not on the dataLayer.push.

As a consequence, when you write your own click handlers your are yourself responsible to make sure your tags are actually fired.

If you use the built-in click handler you can configure a delay to make sure your tag has time to fire before the link redirects:

Since link clicks usually cause the browser to load a new page and interrupt any pending HTTP request, you have the option to add a small delay to allow tags fired by Tag Manager to execute properly before redirecting to the next page. Checking the “Wait For Tags” option will delay opening of links until all tags have fired or the specified timeout has elapsed, whichever comes first.

You should be able to mix both methods (push data on the click, but still use the "native" link click handler for the event).

You can also try to specify "beacon" as the transport method in your Google Analytics tags, on browsers that support this (which I think is only Chrome at the moment) GA will then use the navigator.sendBeacon interface, which sends the data even in case the page unloads.

You might think that Google's solution is not very elegant (but the simple delay has the advantage that it works for all tags, not just for GA), but they have not "forgotten" the problem.

Also solutions that combine GA hit callbacks with timeouts that redirects if the callback fails as proposed i.e. by Simo Ahava somewhere should be be doable with GTM, even if they are probably more cumbersome to implement in GA.