function fillLi(words, parent) {
	for(var i = 0; i < words.length; ++i) {
		var li = document.createElement('li');
		li.innerHTML = words[i];
		parent.appendChild(li);
	}
}

function getULS(parent) {
	var lists = parent.getElementsByTagName('li');
	var uls = new Array();
	for(var i = 0; i < lists.length; ++i) {
		uls.push(document.createElement('ul'));
		lists[i].appendChild(uls[i]);
	}
	return uls;
}

function recursive(elem) {
	var childs = elem.childNodes;
	var index = childs.length;
	console.log('NodeName: ' + elem.nodeName + ', NodeType: ' + elem.nodeType + ', Childs Length: ' + childs.length);
	while(index--) {
		if(elem.nodeType === 1) {
			recursive(childs[index]);
		}
	}
}

var mainElem = document.getElementById('center-content');

var h = document.createElement('h1');
h.innerHTML = 'Создание списка с помощью JS';
mainElem.appendChild(h);

var ul = document.createElement('ul');
mainElem.appendChild(ul);

var words = ['Животные', 'Рыбы'];
fillLi(words, ul);

var uls = getULS(ul);
words = ['Млекопитающие', 'Другие'];
fillLi(words, uls[0]);
words = ['Аквариумные', 'Морские'];
fillLi(words, uls[1]);

var secondULS = getULS(uls[0]);
words = ['Коровы', 'Ослы', 'Собаки', 'Тигры'];
fillLi(words, secondULS[0]);
words = ['Змеи', 'Птицы', 'Ящерицы'];
fillLi(words, secondULS[1]);

secondULS = getULS(uls[1]);
words = ['Гуппи', 'Скалярии'];
fillLi(words, secondULS[0]);
words = ['Морская форель'];
fillLi(words, secondULS[1]);

document.addEventListener("DOMContentLoaded", function(event) {
	recursive(document.documentElement);
});