client/lib/post-normalizer/rule-create-better-excerpt.js
function firstElementIsBreakline( dom ) {
	if ( dom.childNodes.length === 0 ) {
		return dom.nodeName === 'BR' && dom;
	}

	return firstElementIsBreakline( dom.firstChild );
}
function firstElementIsBreakline( dom ) {
	if ( dom.childNodes.length === 0 ) {
		return dom.nodeName === 'BR' && dom;
	}

	return firstElementIsBreakline( dom.firstChild );
}
Returns the node if first element ( checking nested ) is a br
else returns falsy