昨晚在發(fā)布這個(gè)問題后,關(guān)了電腦后,突發(fā)奇想的手寫一段JS代碼,然后到今天下班了再小修小改了下,發(fā)現(xiàn)可以了
具體思路是通過在css里就把每一個(gè)li里的子元素高度設(shè)為目標(biāo)高度,然后就用JS來操作,不寫每個(gè)li的移出事件,只寫移入事件`
下面是我的JS代碼
var oNav = document.getElementById("nav"),

oUl = oNav.getElementsByTagName("ul")[0],
aLi = oUl.children;

var onoff = true,num = 0;
for (var i = 0; i < aLi.length; i++) {

aLi[i].index = i;
aLi[i].onmouseenter = function(){
    if( aLi[this.index].getAttribute("class")==="fl conversion" ){
        if( onoff ){
            this.children[1].style.height = "0";
            this.children[1].style.display = "block";
            animate(aLi[this.index].children[1],"height",232,500);
            num = this.index;
            onoff = false;
        }else{
            aLi[num].children[1].style.display = "none";
            num  = this.index;
            aLi[num].children[1].style.display = "block";
        }
    }else{
        animate(aLi[num].children[1],"height",0,500);
        onoff = true;
    }
};
oUl.onmouseleave = function () {
    animate(aLi[num].children[1],"height",0,500);
    onoff = true;
}

}
如果您發(fā)現(xiàn)有問題,歡迎指出并指正,謝謝