JS Truncate String Function

truncateString.js

function truncateString(str, len, suffix) {
	var suffix = suffix || "...";
	var len = len || 10;
	
	if (str.length <= len) {
		return str;
	} else {
		return str.slice(0, len - suffix.length) + suffix;
	}
}

/* Examples */
truncateString("1234567890abcdefghij1234567890abcdefghij");
truncateString("1234567890abcdefghij1234567890abcdefghij",20);
truncateString("1234567890abcdefghij1234567890abcdefghij",11,"(truncated)");
truncateString("1234567890abcdefghij1234567890abcdefghij",20,"(truncated)");

And this is GTM Custom Javascript variable:

function() {
	var len = 100;
	var suffix = "...";
	var str = "{{YOUR DATALAYER VARIABLE}}";
	
	if (str.length <= len) {
		return str;
	} else {
		return str.slice(0, len - suffix.length) + suffix;
	}
}