练习：javascript分享划过简单效果

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>