                        课程
                    
                        /前端开发
                        
                            /JavaScript
                        
                        /JS动画效果

为什么没效果，求解答

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>鼠标移入</title>
    <style>
        body,div,span{
            margin: 0;
            padding: 0;
        }
        #div1{
            width: 200px;
            height: 200px;
            background-color: red;
            position: relative;
            left: -200px;
        }
        #div1 span{
            width: 40px;
            line-height: 100px;
            background-color: #336699;
            color: #ffffff;
            position: absolute;
            left: 200px;
            top: 50px;
        }
    </style>
</head>
<body>
<div id="div1"><span id="share">分享</span></div>
<script>
    window.onload=function(){
        var moveDiv=document.getElementById("div1");
        moveDiv.mouseover=function(){
            startMove();
        }
    };
    function startMove() {
        var moveDiv=document.getElementById("div1");
        setInterval(function () {
            moveDiv.style.left=moveDiv.offsetLeft+10+'px';
        },30)
    }
</script>
</body>
</html>