利用目标点判断速度speed正负值、利用目标点函数封装传参，
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport"
content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>分享划过简单效果</title>
<style>
#share{width:100px;height:260px;background:#ccc;position:absolute;left:-100px;top:50%;margin-top:-130px; }
#share span{width: 30px;height: 50px;background: orange;display: block;position: absolute;right: -30px;top: 100px;
z-index: 0;border-left: 1px solid #ccc;} </style>
</head>
<body>
<div id="share">
分享
<span></span>
</div>
<script>
var oSpan = document.querySelector('#share span');
var oShare = document.querySelector('#share');
var timer =null;
//利用目标点函数封装传参，
function animate(dest){
dest-oShare.offsetLeft<0?speed=-5:speed=5;
clearInterval(timer);
timer = setInterval(function(){
if(Math.abs(dest-oShare.offsetLeft)<Math.abs(speed)){//显示
oShare.style.left =dest+'px';
clearInterval(timer);
timer = null;
}else {
oShare.style.left =oShare.offsetLeft+speed+'px';
}
},20)
}
oShare.onmouseover=function(){
animate(0);
}
oShare.onmouseout=function(){
animate(-100); }
</script>
</body>
</html>