Issue with `saveas` in javascript

My code in `aspx` file is: <br>

    <input type="file" name="files" id="file" />
    <input type="submit" value="ActionResult" onclick="UpLoad(file)"  />

And my javascript is:

    <script type="text/javascript">
	function UpLoad(file) {
	    var gfile = file.files[0];
	    var gfileSize = gfile.size;
	    var gfileName = gfile.name;
	    var gfileType = gfile.type;
        if (gfileSize > 0) {
	        var x = ('<%=HttpUtility.JavaScriptStringEncode(Server.MapPath("~/App_Data/FileUpload"))%>');
	        var gpath = x + String.fromCharCode(92) + gfileName;
	        gfile.SaveAs(gpath);
	    };         
    };
    </script>

But `SaveAs` throws an error

> 0x800a01b6 - JavaScript runtime error: Object doesn't support property or method 'SaveAs'

<input type="file"  name="file1" id="file1" />
  <input type="button" value="Αποστολή αρχείου" onclick="uploadFile()"/><br />
  <progress id="progressBar" value="0" max="100" style="width:300px;"></progress>
  <h3 id="status"></h3>
  <p id="loaded_n_total"></p>

<script type="text/javascript">
function _(el){
	return document.getElementById(el);
}
function uploadFile(){
	var file = _("file1").files[0];
	// alert(file.name+" | "+file.size+" | "+file.type);
	var formdata = new FormData();
	formdata.append("file1", file);
	var ajax = new XMLHttpRequest();
	ajax.upload.addEventListener("progress", progressHandler, false);
	ajax.addEventListener("load", completeHandler, false);
	ajax.addEventListener("error", errorHandler, false);
	ajax.addEventListener("abort", abortHandler, false);
	ajax.open("POST","http://www.fileupload.ekkeross.com");
	ajax.send(formdata);
}
function progressHandler(event){
	_("loaded_n_total").innerHTML = "Uploaded "+event.loaded+" bytes of "+event.total;
	var percent = (event.loaded / event.total) * 100;
	_("progressBar").value = Math.round(percent);
	_("status").innerHTML = Math.round(percent)+"% uploaded... please wait";
}
function completeHandler(event){
	_("status").innerHTML = event.target.responseText;
	_("progressBar").value = 0;
}
function errorHandler(event){
	_("status").innerHTML =  "Upload Failed  " ;
}
function abortHandler(event){
	_("status").innerHTML = "Upload Aborted";
}
</script>