NOTE when choosing to use a single container across multiple domains, it's important to carefully configure your tags and triggers within Google Tag Manager. Using the default “All Pages” trigger in Google Tag Manager (i.e. $url matches RegEx) will fire tags on all pages of all domains on which your container snippet is deployed.
here is an example of how to use node, node-fs, express and pug to dynamically generate HTML and JS that includes your NEW google tag manager id from your ENV so that if someone clones your @glitch or @zeit node project they DONT get a copy of your GTM ID :)
the top of your rendered html should end up like this note the code between the "Google Tag Manager" comments
the entire project on glitch
the entire project on github
a map jigsaw mashup based on node express pug & prettier (see BADGES below)
mapsaw map tiles from maptiler https://tileserver.maptiler.com/nasa/
see it running on glitch @