这段代码哪里有问题？

window.onload = function(){
            var Lis = document.getElementsByTagName("li");
            if(var i=0 ; i<Lis.length ; i++){
                Lis[i].i = i;
                Lis[i].onmouseover = function(){
                    this.className = "lihover";
                }
                Lis[i].onmouseout = function(){
                    this.className = "";
                }
            }
        }