SOURCE

function delegate(parent,type,id,callback){
  parent.addEventListener(type,function(e){
    if(e.target.id==id){
      callback(e);
    }
  },false);
    parent.attachEvent('on'+type,function(e){
      if(e.srcElement.id==id){
        callback(e);
      }
    },false);
}
var ul=document.getElementsByTagName('ul')[0];
//delegate(ul,'click','li1',function(e){alert(e.target.id);});
ul.addEventListener('click',function(e){
  switch(e.target.id){
    case 'li1':alert('li1');break;
    case 'li2':akert('li2');break;
    default:break;
  }
},false)

<ul>
  <li id='li1'>li1</li>
  <li id='li2'>li2</li>
</ul>

li{
  cursor:pointer;
}