#####This is a simple loading image demo ,you can use it in your xhr request easily .

• First you should generate the cover box like this .

   var str = '<div id="over" class="over"></div><div id="layout" class="layout"><img src="images/loading.gif"/></div>';
  

• Then append this javascript string into you page site, you can append it anywhere you want .

   $("body").append(str);
  

• Then display the loading cover and image

   $("#layout").show();
   $("#over").show();
  

• While request finished you can remove cover loading image easy. use :

   $("#over").remove();
  

• This demo and README depend on jquery syntax , style use bootstrap ; but they are not necessary ,you can also use original javascript syntax to do this.