添加元素

var ulbox =document.getElementByTagName("ul")[0];

function addElement (obj,cont){
var newli = docuemnt.creatElement("li");
newli.setAttribute("class","newli");
newli.innerHtml= cont;
obj.appendChild(newli);
}
addElement (ulbox ,"WHAT MEAN");

<ul class="ul">
<li class="last">last li</li>
</ul>
<button>add new li<button>
<script>
btn.onclick=function  () {
creatEle(ulbox,lili,"hi")
}
function  creatEle(obj,who,cont) {
var newLi = document.createElement("li");
newLi.setAttribute("class", "newli");
newLi.innerHTML = cont;
obj.insertBefore(newLi,who);
}
</script>

function insertAfter(newElement,targetElement)
{
var parent = targetElement.parentNode;
if(parent.lastChild == targetElement)
{
parent.insertBefore(newElement);
}
else
{
parent.insertBefore(newElement,targetElement.nextSibling);
}
}

function addWhat (obj,objtype,cont){
var newele = document.createElement(objtype);
newele.setAttribute("class","newone");
newele.innerHTML=cont;
obj.appendChild(newele);

}

addWhat (divbox,"span","try this result")