wait for button click javascript

<script type="text/javascript">

     function loadCommand(btn) {

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

         btn.innerHTML = '<i class="fa fa-spinner fa-spin fa-lg"></i> Please Wait';

     }

</script>

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<asp:LinkButton ID="btnUpload" runat="server" CssClass="btn-u btn-u-orange btn-u-lg" OnClientClick ="loadCommand(this);" > upload file</asp:LinkButton>

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http://fortawesome.github.io/Font-Awesome/examples/