CVM
commented
10 years ago GitHub seems to have eaten the code in your post, but I'd guess what you're saying is motivated by discussion in this G+ post.
Brian's code illustrates how to do a dataLayer.push() when you're not confident that the dataLayer is within current scope or think it might have been set to be something else other than an array. It can also help in situations where GTM has been declared in the wrong place, causing dataLayer.push() calls to occur prior to gtm.js loading.
This extension will always put gtm.js in the correct place, so dataLayer.push() calls anywhere in the body below this point should reliably queue up - you won't be able to push before the initial declaration.
In terms of scope, the dataLayer is declared globally, as normal. You can reference it from within other JavaScript functions without any problems, provided that it has not been overwritten, so prefixing with window. shouldn't be necessary. Example below:
<script>
dataLayer = [];
</script>
...
<script>
function fireEvent(eventName) {
dataLayer.push({'event':eventName});
}
fireEvent('my_special_event');
</script>Rather than add further code to every dataLayer.push() in order to guard against possible misuse, I feel that the edge case would be better dealt with by writing good code and not destroying it in the first place. No code within the extension will be doing this and it's very unlikely other extensions will be using the variable name for anything else.
phildpearce
Change
To...
This reduces the chance of conflicts if dataLayer is called by onload video events later in the page.
Also using the "window." means that if the dataLayer loads in a frame it wont trigger or be overwritten.