gtm-macros.js

// Macro: "data-track-gtm - get from element"
// Returns: Boolean - does this element, or one of its parents, have a data-track-gtm attribute?
function() {
	var isSet = function(val) {
		return val !== null && val !== '';
	};
	var el = {{element}};
	var val = el.getAttribute('data-track-gtm');

	while (el && el !== document.body && !isSet(val)) {
		el = el.parentElement;
		val = el.getAttribute('data-track-gtm'); 
	}

	return isSet(val) ? val : false;
}

// Macro: "has data-track-gtm attribute"
// Returns: Boolean - does this element, or one of its parents, have a data-track-gtm attribute?
function() {
	return !!{{data-track-gtm - get from element}};
}

// Macro: "data-track-gtm - event action"
// Returns: String
// Is only run if "has data-track-gtm attribute" returns true
function() {
	val = {{data-track-gtm - get from element}};
	return val[1] ? val[1] : false;
}

This is awesome. I made a small change to Macro: "data-track-gtm - event action" to return the full parameter value, rather than a single character. The updated Macro is visible here: https://gist.github.com/mitchdaniels/8651603

(Not sure how best to collaborate on this kind of stuff over Gist. Your feedback is welcome.)