Find The Size Of File Before Saving Using Html5 & Javascript

<input type="file" id="fileUpload" onchange="GetSize()" />
<script type="text/javascript">
       function GetSize() {
           var fileUpload = document.getElementById("fileUpload");
           if (typeof (fileUpload.files) != "undefined") {
               var size = parseFloat(fileUpload.files[0].size / 1024).toFixed(2);
               alert(size + " KB");
           } else {
               alert("Sorry! This browser does not support HTML5.");
           }
       }
</script>