[monolithed]

<ul id="ul">
  <li>0</li>
  <li>1</li>
  <li>3</li>
  <li>4</li>  
</ul>

<script>
var ul = document.getElementById('ul');
var li = document.createElement('li');
li.innerHTML = '2';

ul.insertBefore(li, ul.getElementsByTagName('li')[2]);
</script>