应该来说这是两两配对的时间
mouseenter和mouseleave是只对选中的元素的生效
mouseenter
mouseleave
mouseover和mouseout是只对选中的元素及其子元素生效
mouseover
mouseout
<iframe width="100%" height="300" src="//jsfiddle.net/xiadd/4hno1wgf/embedded/" allowfullscreen="allowfullscreen" frameborder="0"></iframe>
