javascript: How to upload a file on the click of a button.

<script type="text/javascript">

function loadCommand(btn) {

document.getElementById("fiUpload").click();

}

function AlertFilesize(ClientID) {

if (window.ActiveXObject) {

var fso = new ActiveXObject("Scripting.FileSystemObject");

var filepath = ClientID.value;

var thefile = fso.getFile(filepath);

var sizeinbytes = thefile.size;

} else {

var sizeinbytes = ClientID.files[0].size;

}

var fSExt = new Array('Bytes', 'KB', 'MB', 'GB');

fSize = sizeinbytes / 1024; i = 0;

if (Math.round(fSize * 100) / 100 >= 7168) {

ClientID.value = null;

alert("ขนาดเกิน:" + fSize);

}

document.getElementById("btnLoad").innerHTML = '<i class="fa fa-spinner fa-spin fa-lg"></i> Please Wait';

document.getElementById("btnUpload").click();

}

</script>

<asp:FileUpload ID="fiUpload" runat="server" Width="455px"   style ="display:none" onchange="AlertFilesize(this);" />

<asp:LinkButton ID="btnUpload" runat="server"  style ="display:none"   ></asp:LinkButton>                                      

<input id ="btnLoad" type ="button" onclick="loadCommand(this); return;" value ="Upload File" />

************** VB.net ****************

    Protected Sub btnUpload_Click(sender As Object, e As EventArgs) Handles btnUpload.Click

        fiUpload.SaveAs(Server.MapPath(fiUpload.FileName))

    End Sub