怎么利用JS将下面三个小方块中的图片通过onmouseover()将图片显示于上面的大方块中？

html：

 <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Photo Gallery</title>
    <link rel="stylesheet" href="css/gallery.css">
    <script src = "js/gallery.js"></script>
</head>
<body onload="load()">

    <div id = "image">
        Hover over an image below to display here.
    </div>

    <img class = "preview" alt = "Styling with a Bandana" src = "https://s3-us-west-2.amazonaws.com/s.cdpn.io/389177/bacon.jpg" onmouseover = "upDate(this)" onmouseout = "unDo()" >

    <img class = "preview" alt = "With My Boy" src = "https://s3-us-west-2.amazonaws.com/s.cdpn.io/389177/bacon2.JPG" onmouseover = "upDate(this)" onmouseout = "unDo()">

    <img class = "preview" src = "https://s3-us-west-2.amazonaws.com/s.cdpn.io/389177/bacon3.jpg" alt = "Young Puppy" onmouseover = "upDate(this)" onmouseout = "unDo()">

</body>
</html>

css：

 body{
        margin: 2%;
        border: 1px solid black;
        background-color: #b3b3b3;
}
#image{
    line-height:650px;
        width: 575px;
    height: 650px;
        border:5px solid black;
        margin:0 auto;
    background-color: #8e68ff;
    background-image: url('');
    background-repeat: no-repeat;
    color:#FFFFFF;
    text-align: center;
    background-size: 100%;
    margin-bottom:25px;
    font-size: 150%;
}
.preview{
        width:10%;
        margin-left:17%;
    border: 10px solid black;
}
img{
        width:95%;
}

图片说明

鼠标移动到图片上时 ,把这个节点复制到div中,包含节点内容 ,,如果移动之后小图不需要,那就删除这个节点,或者设置visible:hidden;



     function upDate(img) {
        document.getElementById('image').innerHTML='<img src="'+img.src+'"/>'
    }在这里书写代码片

把三张图片加到这个框框里面，并且都设置程display：none；鼠标经过就把那一张显示出来，移出在隐藏

 function upDate(previewPic) {

    var div = document.getElementById("image");

    div.style.backgroundImage = 'URL(' + previewPic.src + ')';
    div.innerHTML = previewPic.alt;
   }