为什么和标准代码基本一样的键盘却没有办法执行出结果。在调试中index的值利用console显示不出来
window.onload=dropdown;
function dropdown(){
var showbox=document.getElementById("showbox"),
lists=document.getElementById("lists"),
tzj=document.getElementsByTagName("li");
//鼠标点击功能
showbox.onclick=function(event){
event=event||window.event
if(event.stopPropagation){
event.stopPropagation();
}else{
event.cancelBubble=true;
}
lists.style.display="block"
}
for(i=0,j=tzj.length;i<j;i++){
tzj[i].onmouseover=function(){
this.style.background="#ccc";
}
tzj[i].onmouseout=function(){
this.style.background="white";
}
tzj[i].onclick=function(e){
e=event||window.event
var classify=document.getElementById("classify")
if(e.stopPropagation){
e.stopPropagation();
}else{
e.cancelBubble=true;
}
classify.innerHTML=this.innerHTML
lists.style.display="none";
}
}
document.onclick=function(){
lists.style.display="none";
}
//键盘功能
document.onkeyup=function(event){
event=event||window.event
var index=-1;
for(i=0,j=tzj.length;i++;i<j){
if(event.keyCode==40){
index++;
console.log(index)
if(index>=tzj.length){
index=0;
}
tzj[index].style.background="#ccc";
}
if(event.keyCode==38){
if(index<=0){
index=as.length;
}
index--;
tzj[index].style.background="#ccc";
}
}
}
}
