一个div里有多个a标签，改变a标签的字体颜色方法

<script type="text/javascript">
var all=document.getElementById("big");
var allDiv=all.getElementsByTagName("div");

for(var i=1;i<allDiv.length+1;i++){
allDiv[i-1].onmouseover=function(){
var alla=this.getElementsByTagName("a");
for(var ele in alla){
alla[ele].style.color="red";
}
}
allDiv[i-1].onmouseout=function(){
var alla=this.getElementsByTagName("a");
for(var ele in alla){
alla[ele].style.color=" ghostwhite";
}
}
}