How to preview a image before upload

How to preview a image before upload ?


<\script type="text/javascript">
        function readURL(input) {
            if (input.files && input.files[0]) {
                var reader = new FileReader();

                reader.onload = function (e) {
                    $('#blah').attr('src', e.target.result);
                }

                reader.readAsDataURL(input.files[0]);
            }
        }
    <\/script>

<\body>
    <\form id="form1" runat="server">
        <\input type='file' onchange="readURL(this);" />
        <\img id="blah" src="#" alt="your image" />
    <\/form>
<\/body>

Note :- Before using this code remove "\" from the tags