client/lib/analytics/ad-tracking.js
function floodlightUserParams() {
	const params = {};

	const currentUser = user.get();
	if ( currentUser ) {
		params.u4 = hashPii( currentUser.ID );
	}

	const anonymousUserId = tracksAnonymousUserId();
	if ( anonymousUserId ) {
		params.u5 = anonymousUserId;
	}

	return params;
}
function floodlightUserParams() {
	const params = {};

	const currentUser = user.get();
	if ( currentUser ) {
		params.u4 = hashPii( currentUser.ID );
	}

	const anonymousUserId = tracksAnonymousUserId();
	if ( anonymousUserId ) {
		params.u5 = anonymousUserId;
	}

	return params;
}
Returns an object with DCM Floodlight user params

@returns {Object} With the WordPress.com user id and/or the logged out Tracks id