JS之下拉菜单案例鼠标经过显示

// 1. 获取元素
var nav = document.querySelector('.nav');
var lis = nav.children; //得到4个小li
// 2.循环注册事件
for(var i=0;i<lis.length;i++){
lis[i].onmouseover = function(){
this.children[1].style.display = 'block';
}
lis[i].onmouseout = function(){
this.children[1].style.display = 'none';
}
}