mouseenter:只有移入当前元素才会触发，对应mouseleave

 

                        hover使用的是mouseenter与mouseleave

mouseover：在移入子元素时也会触发，对应mouseout

	<div id="div1">div1<div id="div2">div2</div></div><div id="div3">div3<div id="div4">div4</div></div>

			#div1,#div3 {width: 200px;height: 200px;background: #bfa;position: absolute;}#div3{left: 250px;}#div2,#div4 {width: 100px;height: 100px;background: skyblue;position: relative;top: 50px;left: 50px;}

在进入子元素的时候 也会使得出现进入 离开的触发 

			$('#div1').mouseover(function(){console.log('mouseover进入')}).mouseout(function(){console.log('mouseout离开')})$('#div3').mouseenter(function(){console.log('mouseenter进入')}).mouseleave(function(){console.log('mouseleave离开')})

	//可以加多个document.getElementById('div1').addEventListener('click',function(){console.log('click1');})document.getElementById('div1').addEventListener('click',function(){console.log('click2');})

		//不可以两次document.getElementById('div1').onclick=function(){console.log('click1');}//只有一个生效document.getElementById('div1').onclick=function(){console.log('click2');}