每天一个JavaScript实例-获取元素当前高度

<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>每天一个JavaScript实例-获取元素当前高度</title>
<style>
        #date{width:90%;height:25%;padding:10px;background: red;}
</style>
<script>
window.onload = function(){
        var height = getHeight();
        console.log(height);
}
function getHeight(){
        var height = 0;
        var div = document.getElementById("date").getBoundingClientRect();
        if(div.height){
                height = div.height;
        }else{
                height = div.bottom - div.top;
        }
        return height;
}
</script>
</head>

<body>
<div >
<div id = "date">
</div>
</div>
</body>
</html>