ajax请求加载Loading或错误提示

<div id="loadingDiv" style="color:#f39800;">Loading...</div>

<script type="text/javascript">

var $loading = $('#loadingDiv').hide();
$(document).ajaxStart(function () {
$('#loadingDiv').css("position", "absolute");
$('#loadingDiv').css("top", Math.max(0, (($(window).height() - $('#loadingDiv').outerHeight()) / 2) +
$(window).scrollTop()) + "px");
$('#loadingDiv').css("left", Math.max(0, (($(window).width() - $('#loadingDiv').outerWidth()) / 2) +
$(window).scrollLeft()) + "px");
$('#loadingDiv').show();
})
.ajaxStop(function () {
$('#loadingDiv').hide();
});
$(document).ajaxError(function (event, jqXHR, request, settings) {
var text = jqXHR.statusText + "(" + jqXHR.status + ")";
if (jqXHR.responseJSON)
text = jqXHR.responseJSON.message;
alert('操作出现异常：' + text + '重试后仍出现请联系开发');
});
</script>