在a标签上加事件

a-hover.js

var dropdown = function(e) {
	e = e || window.event;
	var targ = e.target || e.srcElement;
	if(targ.tagName === "A" && targ.parentNode.parentNode.className === "general"){
		var second = targ.parentNode.getElementsByClassName(targ.parentNode.className)[0];		
		var status = window.getComputedStyle(second,"").getPropertyValue('display');
		if(status ==="none") {
			second.style.display = "inline-block";
		}
	}
	e.preventDefault();
}
var leave = function(e) {
	e = e || window.event;
	var targ = e.target || e.srcElement;
	if(targ.tagName === "A" && targ.parentNode.parentNode.className === "general"){
		var second = targ.parentNode.getElementsByClassName(targ.parentNode.className)[0];		
		second.style.display = "none";
	}
	e.preventDefault();
}
var ul = document.getElementsByClassName('general');
ul[0].addEventListener('mouseover', dropdown, false);
ul[0].addEventListener('mouseout',leave,false);