show image from local file for preview, how?

submit

<textarea>CKEDITOR.replace()ckeditor\plugins\image\dialogs\image.jsUpload

<head>
<style type="text/css">
    #prevImage {
        border: 3px solid #ccc;
    }
</style>

<script type="text/javascript">
    function previewImg(file)
    {
        var elm=document.getElementById('prevImage');
        if (elm) {
            elm.src=file.files.item(0).getAsDataURL();
        }
        if (elm.src.length > 0)
            elm.style.display = 'block';
    }
</script>
</head>

<body>
<div id="upload-preview">
    <img id="prevImage" style="display:none;" />
    <form>
        <input type="file" name="imgFile" onchange="previewImg(this);" style="font-family: Verdana, Arial; font-size: 12px;" />
    </form>
</div>
</body>