show image in client not need upload server

<script type="text/javascript">

function file_change(f){

    var reader = new FileReader();

    reader.onload = function (e) {

        var img = document.getElementById("img");

        img.src = e.target.result;

        img.style.display = "inline";

    };

    reader.readAsDataURL(f.files[0]);

}

</script>

<input id="f" type="file" onchange="file_change(this)" style="display: none" /><input type="button" value="Chọn ảnh" onclick="document.getElementById('f').click()" />

<img id="img" style="display: none" />