利用JavaScript的if语句判断元素显示隐藏

<html>
<head>
<meta charset="utf-8">
<title>无标题文档</title>
<style type="text/css">
    #div1 {
        width: 100px;
        height:100px;
        background: red;
        display: none;
    }
</style>
<script>
    function showhide(){
        var odiv=document.getElementById('div1');
        if(odiv.style.display=='block')
            {
                odiv.style.display='none';
            }
        else{
            odiv.style.display='block';
        }
    }
</script>
</head>

<body>
<input type="button" value="显示隐藏" onClick="showhide()" />
<div id="div1">
    
</div>
</body>
</html>